From patchwork Fri May 13 22:42:03 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Maciej W. Rozycki" X-Patchwork-Id: 572481 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 55A9CC433FE for ; Fri, 13 May 2022 22:42:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378913AbiEMWmI (ORCPT ); Fri, 13 May 2022 18:42:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48520 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1349751AbiEMWmG (ORCPT ); Fri, 13 May 2022 18:42:06 -0400 Received: from angie.orcam.me.uk (angie.orcam.me.uk [78.133.224.34]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 6C8572B266; Fri, 13 May 2022 15:42:04 -0700 (PDT) Received: by angie.orcam.me.uk (Postfix, from userid 500) id B7A3E92009D; Sat, 14 May 2022 00:42:03 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by angie.orcam.me.uk (Postfix) with ESMTP id B231B92009B; Fri, 13 May 2022 23:42:03 +0100 (BST) Date: Fri, 13 May 2022 23:42:03 +0100 (BST) From: "Maciej W. Rozycki" To: Jonathan Corbet , Greg Kroah-Hartman , Jiri Slaby cc: Stephen Rothwell , Andy Shevchenko , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, linux-next@vger.kernel.org Subject: [PATCH 1/3] Documentation: Move Oxford Semiconductor PCIe (Tornado) 950 to misc-devices In-Reply-To: Message-ID: References: User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org Documentation/tty has been moved to driver-api, which is not suitable for user documentation, so move the Oxford Semiconductor PCIe (Tornado) 950 description to misc-devices instead. Signed-off-by: Maciej W. Rozycki --- Documentation/misc-devices/oxsemi-tornado.rst | 129 ++++++++++++++++++++ Documentation/tty/device_drivers/oxsemi-tornado.rst | 129 -------------------- 2 files changed, 129 insertions(+), 129 deletions(-) linux-doc-oxsemi-tornado-move.diff Index: linux-macro/Documentation/misc-devices/oxsemi-tornado.rst =================================================================== --- /dev/null +++ linux-macro/Documentation/misc-devices/oxsemi-tornado.rst @@ -0,0 +1,129 @@ +.. SPDX-License-Identifier: GPL-2.0 + +==================================================================== +Notes on Oxford Semiconductor PCIe (Tornado) 950 serial port devices +==================================================================== + +Oxford Semiconductor PCIe (Tornado) 950 serial port devices are driven +by a fixed 62.5MHz clock input derived from the 100MHz PCI Express clock. + +The baud rate produced by the baud generator is obtained from this input +frequency by dividing it by the clock prescaler, which can be set to any +value from 1 to 63.875 in increments of 0.125, and then the usual 16-bit +divisor is used as with the original 8250, to divide the frequency by a +value from 1 to 65535. Finally a programmable oversampling rate is used +that can take any value from 4 to 16 to divide the frequency further and +determine the actual baud rate used. Baud rates from 15625000bps down +to 0.933bps can be obtained this way. + +By default the oversampling rate is set to 16 and the clock prescaler is +set to 33.875, meaning that the frequency to be used as the reference +for the usual 16-bit divisor is 115313.653, which is close enough to the +frequency of 115200 used by the original 8250 for the same values to be +used for the divisor to obtain the requested baud rates by software that +is unaware of the extra clock controls available. + +The oversampling rate is programmed with the TCR register and the clock +prescaler is programmed with the CPR/CPR2 register pair[1][2][3][4]. +To switch away from the default value of 33.875 for the prescaler the +the enhanced mode has to be explicitly enabled though, by setting bit 4 +of the EFR. In that mode setting bit 7 in the MCR enables the prescaler +or otherwise it is bypassed as if the value of 1 was used. Additionally +writing any value to CPR clears CPR2 for compatibility with old software +written for older conventional PCI Oxford Semiconductor devices that do +not have the extra prescaler's 9th bit in CPR2, so the CPR/CPR2 register +pair has to be programmed in the right order. + +By using these parameters rates from 15625000bps down to 1bps can be +obtained, with either exact or highly-accurate actual bit rates for +standard and many non-standard rates. + +Here are the figures for the standard and some non-standard baud rates +(including those quoted in Oxford Semiconductor documentation), giving +the requested rate (r), the actual rate yielded (a) and its deviation +from the requested rate (d), and the values of the oversampling rate +(tcr), the clock prescaler (cpr) and the divisor (div) produced by the +new `get_divisor' handler: + +r: 15625000, a: 15625000.00, d: 0.0000%, tcr: 4, cpr: 1.000, div: 1 +r: 12500000, a: 12500000.00, d: 0.0000%, tcr: 5, cpr: 1.000, div: 1 +r: 10416666, a: 10416666.67, d: 0.0000%, tcr: 6, cpr: 1.000, div: 1 +r: 8928571, a: 8928571.43, d: 0.0000%, tcr: 7, cpr: 1.000, div: 1 +r: 7812500, a: 7812500.00, d: 0.0000%, tcr: 8, cpr: 1.000, div: 1 +r: 4000000, a: 4000000.00, d: 0.0000%, tcr: 5, cpr: 3.125, div: 1 +r: 3686400, a: 3676470.59, d: -0.2694%, tcr: 8, cpr: 2.125, div: 1 +r: 3500000, a: 3496503.50, d: -0.0999%, tcr: 13, cpr: 1.375, div: 1 +r: 3000000, a: 2976190.48, d: -0.7937%, tcr: 14, cpr: 1.500, div: 1 +r: 2500000, a: 2500000.00, d: 0.0000%, tcr: 10, cpr: 2.500, div: 1 +r: 2000000, a: 2000000.00, d: 0.0000%, tcr: 10, cpr: 3.125, div: 1 +r: 1843200, a: 1838235.29, d: -0.2694%, tcr: 16, cpr: 2.125, div: 1 +r: 1500000, a: 1492537.31, d: -0.4975%, tcr: 5, cpr: 8.375, div: 1 +r: 1152000, a: 1152073.73, d: 0.0064%, tcr: 14, cpr: 3.875, div: 1 +r: 921600, a: 919117.65, d: -0.2694%, tcr: 16, cpr: 2.125, div: 2 +r: 576000, a: 576036.87, d: 0.0064%, tcr: 14, cpr: 3.875, div: 2 +r: 460800, a: 460829.49, d: 0.0064%, tcr: 7, cpr: 3.875, div: 5 +r: 230400, a: 230414.75, d: 0.0064%, tcr: 14, cpr: 3.875, div: 5 +r: 115200, a: 115207.37, d: 0.0064%, tcr: 14, cpr: 1.250, div: 31 +r: 57600, a: 57603.69, d: 0.0064%, tcr: 8, cpr: 3.875, div: 35 +r: 38400, a: 38402.46, d: 0.0064%, tcr: 14, cpr: 3.875, div: 30 +r: 19200, a: 19201.23, d: 0.0064%, tcr: 8, cpr: 3.875, div: 105 +r: 9600, a: 9600.06, d: 0.0006%, tcr: 9, cpr: 1.125, div: 643 +r: 4800, a: 4799.98, d: -0.0004%, tcr: 7, cpr: 2.875, div: 647 +r: 2400, a: 2400.02, d: 0.0008%, tcr: 9, cpr: 2.250, div: 1286 +r: 1200, a: 1200.00, d: 0.0000%, tcr: 14, cpr: 2.875, div: 1294 +r: 300, a: 300.00, d: 0.0000%, tcr: 11, cpr: 2.625, div: 7215 +r: 200, a: 200.00, d: 0.0000%, tcr: 16, cpr: 1.250, div: 15625 +r: 150, a: 150.00, d: 0.0000%, tcr: 13, cpr: 2.250, div: 14245 +r: 134, a: 134.00, d: 0.0000%, tcr: 11, cpr: 2.625, div: 16153 +r: 110, a: 110.00, d: 0.0000%, tcr: 12, cpr: 1.000, div: 47348 +r: 75, a: 75.00, d: 0.0000%, tcr: 4, cpr: 5.875, div: 35461 +r: 50, a: 50.00, d: 0.0000%, tcr: 16, cpr: 1.250, div: 62500 +r: 25, a: 25.00, d: 0.0000%, tcr: 16, cpr: 2.500, div: 62500 +r: 4, a: 4.00, d: 0.0000%, tcr: 16, cpr: 20.000, div: 48828 +r: 2, a: 2.00, d: 0.0000%, tcr: 16, cpr: 40.000, div: 48828 +r: 1, a: 1.00, d: 0.0000%, tcr: 16, cpr: 63.875, div: 61154 + +With the baud base set to 15625000 and the unsigned 16-bit UART_DIV_MAX +limitation imposed by `serial8250_get_baud_rate' standard baud rates +below 300bps become unavailable in the regular way, e.g. the rate of +200bps requires the baud base to be divided by 78125 and that is beyond +the unsigned 16-bit range. The historic spd_cust feature can still be +used by encoding the values for, the prescaler, the oversampling rate +and the clock divisor (DLM/DLL) as follows to obtain such rates if so +required: + + 31 29 28 20 19 16 15 0 ++-----+-----------------+-------+-------------------------------+ +|0 0 0| CPR2:CPR | TCR | DLM:DLL | ++-----+-----------------+-------+-------------------------------+ + +Use a value such encoded for the `custom_divisor' field along with the +ASYNC_SPD_CUST flag set in the `flags' field in `struct serial_struct' +passed with the TIOCSSERIAL ioctl(2), such as with the setserial(8) +utility and its `divisor' and `spd_cust' parameters, and the select +the baud rate of 38400bps. Note that the value of 0 in TCR sets the +oversampling rate to 16 and prescaler values below 1 in CPR2/CPR are +clamped by the driver to 1. + +For example the value of 0x1f4004e2 will set CPR2/CPR, TCR and DLM/DLL +respectively to 0x1f4, 0x0 and 0x04e2, choosing the prescaler value, +the oversampling rate and the clock divisor of 62.500, 16 and 1250 +respectively. These parameters will set the baud rate for the serial +port to 62500000 / 62.500 / 1250 / 16 = 50bps. + +References: + +[1] "OXPCIe200 PCI Express Multi-Port Bridge", Oxford Semiconductor, + Inc., DS-0045, 10 Nov 2008, Section "950 Mode", pp. 64-65 + +[2] "OXPCIe952 PCI Express Bridge to Dual Serial & Parallel Port", + Oxford Semiconductor, Inc., DS-0046, Mar 06 08, Section "950 Mode", + p. 20 + +[3] "OXPCIe954 PCI Express Bridge to Quad Serial Port", Oxford + Semiconductor, Inc., DS-0047, Feb 08, Section "950 Mode", p. 20 + +[4] "OXPCIe958 PCI Express Bridge to Octal Serial Port", Oxford + Semiconductor, Inc., DS-0048, Feb 08, Section "950 Mode", p. 20 + +Maciej W. Rozycki Index: linux-macro/Documentation/tty/device_drivers/oxsemi-tornado.rst =================================================================== --- linux-macro.orig/Documentation/tty/device_drivers/oxsemi-tornado.rst +++ /dev/null @@ -1,129 +0,0 @@ -.. SPDX-License-Identifier: GPL-2.0 - -==================================================================== -Notes on Oxford Semiconductor PCIe (Tornado) 950 serial port devices -==================================================================== - -Oxford Semiconductor PCIe (Tornado) 950 serial port devices are driven -by a fixed 62.5MHz clock input derived from the 100MHz PCI Express clock. - -The baud rate produced by the baud generator is obtained from this input -frequency by dividing it by the clock prescaler, which can be set to any -value from 1 to 63.875 in increments of 0.125, and then the usual 16-bit -divisor is used as with the original 8250, to divide the frequency by a -value from 1 to 65535. Finally a programmable oversampling rate is used -that can take any value from 4 to 16 to divide the frequency further and -determine the actual baud rate used. Baud rates from 15625000bps down -to 0.933bps can be obtained this way. - -By default the oversampling rate is set to 16 and the clock prescaler is -set to 33.875, meaning that the frequency to be used as the reference -for the usual 16-bit divisor is 115313.653, which is close enough to the -frequency of 115200 used by the original 8250 for the same values to be -used for the divisor to obtain the requested baud rates by software that -is unaware of the extra clock controls available. - -The oversampling rate is programmed with the TCR register and the clock -prescaler is programmed with the CPR/CPR2 register pair[1][2][3][4]. -To switch away from the default value of 33.875 for the prescaler the -the enhanced mode has to be explicitly enabled though, by setting bit 4 -of the EFR. In that mode setting bit 7 in the MCR enables the prescaler -or otherwise it is bypassed as if the value of 1 was used. Additionally -writing any value to CPR clears CPR2 for compatibility with old software -written for older conventional PCI Oxford Semiconductor devices that do -not have the extra prescaler's 9th bit in CPR2, so the CPR/CPR2 register -pair has to be programmed in the right order. - -By using these parameters rates from 15625000bps down to 1bps can be -obtained, with either exact or highly-accurate actual bit rates for -standard and many non-standard rates. - -Here are the figures for the standard and some non-standard baud rates -(including those quoted in Oxford Semiconductor documentation), giving -the requested rate (r), the actual rate yielded (a) and its deviation -from the requested rate (d), and the values of the oversampling rate -(tcr), the clock prescaler (cpr) and the divisor (div) produced by the -new `get_divisor' handler: - -r: 15625000, a: 15625000.00, d: 0.0000%, tcr: 4, cpr: 1.000, div: 1 -r: 12500000, a: 12500000.00, d: 0.0000%, tcr: 5, cpr: 1.000, div: 1 -r: 10416666, a: 10416666.67, d: 0.0000%, tcr: 6, cpr: 1.000, div: 1 -r: 8928571, a: 8928571.43, d: 0.0000%, tcr: 7, cpr: 1.000, div: 1 -r: 7812500, a: 7812500.00, d: 0.0000%, tcr: 8, cpr: 1.000, div: 1 -r: 4000000, a: 4000000.00, d: 0.0000%, tcr: 5, cpr: 3.125, div: 1 -r: 3686400, a: 3676470.59, d: -0.2694%, tcr: 8, cpr: 2.125, div: 1 -r: 3500000, a: 3496503.50, d: -0.0999%, tcr: 13, cpr: 1.375, div: 1 -r: 3000000, a: 2976190.48, d: -0.7937%, tcr: 14, cpr: 1.500, div: 1 -r: 2500000, a: 2500000.00, d: 0.0000%, tcr: 10, cpr: 2.500, div: 1 -r: 2000000, a: 2000000.00, d: 0.0000%, tcr: 10, cpr: 3.125, div: 1 -r: 1843200, a: 1838235.29, d: -0.2694%, tcr: 16, cpr: 2.125, div: 1 -r: 1500000, a: 1492537.31, d: -0.4975%, tcr: 5, cpr: 8.375, div: 1 -r: 1152000, a: 1152073.73, d: 0.0064%, tcr: 14, cpr: 3.875, div: 1 -r: 921600, a: 919117.65, d: -0.2694%, tcr: 16, cpr: 2.125, div: 2 -r: 576000, a: 576036.87, d: 0.0064%, tcr: 14, cpr: 3.875, div: 2 -r: 460800, a: 460829.49, d: 0.0064%, tcr: 7, cpr: 3.875, div: 5 -r: 230400, a: 230414.75, d: 0.0064%, tcr: 14, cpr: 3.875, div: 5 -r: 115200, a: 115207.37, d: 0.0064%, tcr: 14, cpr: 1.250, div: 31 -r: 57600, a: 57603.69, d: 0.0064%, tcr: 8, cpr: 3.875, div: 35 -r: 38400, a: 38402.46, d: 0.0064%, tcr: 14, cpr: 3.875, div: 30 -r: 19200, a: 19201.23, d: 0.0064%, tcr: 8, cpr: 3.875, div: 105 -r: 9600, a: 9600.06, d: 0.0006%, tcr: 9, cpr: 1.125, div: 643 -r: 4800, a: 4799.98, d: -0.0004%, tcr: 7, cpr: 2.875, div: 647 -r: 2400, a: 2400.02, d: 0.0008%, tcr: 9, cpr: 2.250, div: 1286 -r: 1200, a: 1200.00, d: 0.0000%, tcr: 14, cpr: 2.875, div: 1294 -r: 300, a: 300.00, d: 0.0000%, tcr: 11, cpr: 2.625, div: 7215 -r: 200, a: 200.00, d: 0.0000%, tcr: 16, cpr: 1.250, div: 15625 -r: 150, a: 150.00, d: 0.0000%, tcr: 13, cpr: 2.250, div: 14245 -r: 134, a: 134.00, d: 0.0000%, tcr: 11, cpr: 2.625, div: 16153 -r: 110, a: 110.00, d: 0.0000%, tcr: 12, cpr: 1.000, div: 47348 -r: 75, a: 75.00, d: 0.0000%, tcr: 4, cpr: 5.875, div: 35461 -r: 50, a: 50.00, d: 0.0000%, tcr: 16, cpr: 1.250, div: 62500 -r: 25, a: 25.00, d: 0.0000%, tcr: 16, cpr: 2.500, div: 62500 -r: 4, a: 4.00, d: 0.0000%, tcr: 16, cpr: 20.000, div: 48828 -r: 2, a: 2.00, d: 0.0000%, tcr: 16, cpr: 40.000, div: 48828 -r: 1, a: 1.00, d: 0.0000%, tcr: 16, cpr: 63.875, div: 61154 - -With the baud base set to 15625000 and the unsigned 16-bit UART_DIV_MAX -limitation imposed by `serial8250_get_baud_rate' standard baud rates -below 300bps become unavailable in the regular way, e.g. the rate of -200bps requires the baud base to be divided by 78125 and that is beyond -the unsigned 16-bit range. The historic spd_cust feature can still be -used by encoding the values for, the prescaler, the oversampling rate -and the clock divisor (DLM/DLL) as follows to obtain such rates if so -required: - - 31 29 28 20 19 16 15 0 -+-----+-----------------+-------+-------------------------------+ -|0 0 0| CPR2:CPR | TCR | DLM:DLL | -+-----+-----------------+-------+-------------------------------+ - -Use a value such encoded for the `custom_divisor' field along with the -ASYNC_SPD_CUST flag set in the `flags' field in `struct serial_struct' -passed with the TIOCSSERIAL ioctl(2), such as with the setserial(8) -utility and its `divisor' and `spd_cust' parameters, and the select -the baud rate of 38400bps. Note that the value of 0 in TCR sets the -oversampling rate to 16 and prescaler values below 1 in CPR2/CPR are -clamped by the driver to 1. - -For example the value of 0x1f4004e2 will set CPR2/CPR, TCR and DLM/DLL -respectively to 0x1f4, 0x0 and 0x04e2, choosing the prescaler value, -the oversampling rate and the clock divisor of 62.500, 16 and 1250 -respectively. These parameters will set the baud rate for the serial -port to 62500000 / 62.500 / 1250 / 16 = 50bps. - -References: - -[1] "OXPCIe200 PCI Express Multi-Port Bridge", Oxford Semiconductor, - Inc., DS-0045, 10 Nov 2008, Section "950 Mode", pp. 64-65 - -[2] "OXPCIe952 PCI Express Bridge to Dual Serial & Parallel Port", - Oxford Semiconductor, Inc., DS-0046, Mar 06 08, Section "950 Mode", - p. 20 - -[3] "OXPCIe954 PCI Express Bridge to Quad Serial Port", Oxford - Semiconductor, Inc., DS-0047, Feb 08, Section "950 Mode", p. 20 - -[4] "OXPCIe958 PCI Express Bridge to Octal Serial Port", Oxford - Semiconductor, Inc., DS-0048, Feb 08, Section "950 Mode", p. 20 - -Maciej W. Rozycki From patchwork Fri May 13 22:42:08 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Maciej W. Rozycki" X-Patchwork-Id: 572480 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 06FDAC4332F for ; Fri, 13 May 2022 22:42:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1384832AbiEMWmU (ORCPT ); Fri, 13 May 2022 18:42:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48950 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1384829AbiEMWmQ (ORCPT ); Fri, 13 May 2022 18:42:16 -0400 Received: from angie.orcam.me.uk (angie.orcam.me.uk [IPv6:2001:4190:8020::34]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 358812B266; Fri, 13 May 2022 15:42:10 -0700 (PDT) Received: by angie.orcam.me.uk (Postfix, from userid 500) id 9295092009E; Sat, 14 May 2022 00:42:08 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by angie.orcam.me.uk (Postfix) with ESMTP id 8B68892009B; Fri, 13 May 2022 23:42:08 +0100 (BST) Date: Fri, 13 May 2022 23:42:08 +0100 (BST) From: "Maciej W. Rozycki" To: Jonathan Corbet , Greg Kroah-Hartman , Jiri Slaby cc: Stephen Rothwell , Andy Shevchenko , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, linux-next@vger.kernel.org Subject: [PATCH 2/3] Documentation: Reformat Oxford Semiconductor PCIe (Tornado) 950 In-Reply-To: Message-ID: References: User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org Reformat Oxford Semiconductor PCIe (Tornado) 950 description in terms of reStructuredText markup, fixing warnings with `make htmldocs'. While at it remove typos: s/the the/the/ and s/the/then/ in lines changed anyway. Signed-off-by: Maciej W. Rozycki --- Documentation/misc-devices/oxsemi-tornado.rst | 136 +++++++++++++------------- 1 file changed, 69 insertions(+), 67 deletions(-) linux-doc-oxsemi-tornado-fix.diff Index: linux-macro/Documentation/misc-devices/oxsemi-tornado.rst =================================================================== --- linux-macro.orig/Documentation/misc-devices/oxsemi-tornado.rst +++ linux-macro/Documentation/misc-devices/oxsemi-tornado.rst @@ -24,15 +24,15 @@ used for the divisor to obtain the reque is unaware of the extra clock controls available. The oversampling rate is programmed with the TCR register and the clock -prescaler is programmed with the CPR/CPR2 register pair[1][2][3][4]. -To switch away from the default value of 33.875 for the prescaler the -the enhanced mode has to be explicitly enabled though, by setting bit 4 -of the EFR. In that mode setting bit 7 in the MCR enables the prescaler -or otherwise it is bypassed as if the value of 1 was used. Additionally -writing any value to CPR clears CPR2 for compatibility with old software -written for older conventional PCI Oxford Semiconductor devices that do -not have the extra prescaler's 9th bit in CPR2, so the CPR/CPR2 register -pair has to be programmed in the right order. +prescaler is programmed with the CPR/CPR2 register pair [OX200]_ [OX952]_ +[OX954]_ [OX958]_. To switch away from the default value of 33.875 for +the prescaler the enhanced mode has to be explicitly enabled though, by +setting bit 4 of the EFR. In that mode setting bit 7 in the MCR enables +the prescaler or otherwise it is bypassed as if the value of 1 was used. +Additionally writing any value to CPR clears CPR2 for compatibility with +old software written for older conventional PCI Oxford Semiconductor +devices that do not have the extra prescaler's 9th bit in CPR2, so the +CPR/CPR2 register pair has to be programmed in the right order. By using these parameters rates from 15625000bps down to 1bps can be obtained, with either exact or highly-accurate actual bit rates for @@ -43,48 +43,50 @@ Here are the figures for the standard an the requested rate (r), the actual rate yielded (a) and its deviation from the requested rate (d), and the values of the oversampling rate (tcr), the clock prescaler (cpr) and the divisor (div) produced by the -new `get_divisor' handler: +new ``get_divisor`` handler: -r: 15625000, a: 15625000.00, d: 0.0000%, tcr: 4, cpr: 1.000, div: 1 -r: 12500000, a: 12500000.00, d: 0.0000%, tcr: 5, cpr: 1.000, div: 1 -r: 10416666, a: 10416666.67, d: 0.0000%, tcr: 6, cpr: 1.000, div: 1 -r: 8928571, a: 8928571.43, d: 0.0000%, tcr: 7, cpr: 1.000, div: 1 -r: 7812500, a: 7812500.00, d: 0.0000%, tcr: 8, cpr: 1.000, div: 1 -r: 4000000, a: 4000000.00, d: 0.0000%, tcr: 5, cpr: 3.125, div: 1 -r: 3686400, a: 3676470.59, d: -0.2694%, tcr: 8, cpr: 2.125, div: 1 -r: 3500000, a: 3496503.50, d: -0.0999%, tcr: 13, cpr: 1.375, div: 1 -r: 3000000, a: 2976190.48, d: -0.7937%, tcr: 14, cpr: 1.500, div: 1 -r: 2500000, a: 2500000.00, d: 0.0000%, tcr: 10, cpr: 2.500, div: 1 -r: 2000000, a: 2000000.00, d: 0.0000%, tcr: 10, cpr: 3.125, div: 1 -r: 1843200, a: 1838235.29, d: -0.2694%, tcr: 16, cpr: 2.125, div: 1 -r: 1500000, a: 1492537.31, d: -0.4975%, tcr: 5, cpr: 8.375, div: 1 -r: 1152000, a: 1152073.73, d: 0.0064%, tcr: 14, cpr: 3.875, div: 1 -r: 921600, a: 919117.65, d: -0.2694%, tcr: 16, cpr: 2.125, div: 2 -r: 576000, a: 576036.87, d: 0.0064%, tcr: 14, cpr: 3.875, div: 2 -r: 460800, a: 460829.49, d: 0.0064%, tcr: 7, cpr: 3.875, div: 5 -r: 230400, a: 230414.75, d: 0.0064%, tcr: 14, cpr: 3.875, div: 5 -r: 115200, a: 115207.37, d: 0.0064%, tcr: 14, cpr: 1.250, div: 31 -r: 57600, a: 57603.69, d: 0.0064%, tcr: 8, cpr: 3.875, div: 35 -r: 38400, a: 38402.46, d: 0.0064%, tcr: 14, cpr: 3.875, div: 30 -r: 19200, a: 19201.23, d: 0.0064%, tcr: 8, cpr: 3.875, div: 105 -r: 9600, a: 9600.06, d: 0.0006%, tcr: 9, cpr: 1.125, div: 643 -r: 4800, a: 4799.98, d: -0.0004%, tcr: 7, cpr: 2.875, div: 647 -r: 2400, a: 2400.02, d: 0.0008%, tcr: 9, cpr: 2.250, div: 1286 -r: 1200, a: 1200.00, d: 0.0000%, tcr: 14, cpr: 2.875, div: 1294 -r: 300, a: 300.00, d: 0.0000%, tcr: 11, cpr: 2.625, div: 7215 -r: 200, a: 200.00, d: 0.0000%, tcr: 16, cpr: 1.250, div: 15625 -r: 150, a: 150.00, d: 0.0000%, tcr: 13, cpr: 2.250, div: 14245 -r: 134, a: 134.00, d: 0.0000%, tcr: 11, cpr: 2.625, div: 16153 -r: 110, a: 110.00, d: 0.0000%, tcr: 12, cpr: 1.000, div: 47348 -r: 75, a: 75.00, d: 0.0000%, tcr: 4, cpr: 5.875, div: 35461 -r: 50, a: 50.00, d: 0.0000%, tcr: 16, cpr: 1.250, div: 62500 -r: 25, a: 25.00, d: 0.0000%, tcr: 16, cpr: 2.500, div: 62500 -r: 4, a: 4.00, d: 0.0000%, tcr: 16, cpr: 20.000, div: 48828 -r: 2, a: 2.00, d: 0.0000%, tcr: 16, cpr: 40.000, div: 48828 -r: 1, a: 1.00, d: 0.0000%, tcr: 16, cpr: 63.875, div: 61154 +:: + + r: 15625000, a: 15625000.00, d: 0.0000%, tcr: 4, cpr: 1.000, div: 1 + r: 12500000, a: 12500000.00, d: 0.0000%, tcr: 5, cpr: 1.000, div: 1 + r: 10416666, a: 10416666.67, d: 0.0000%, tcr: 6, cpr: 1.000, div: 1 + r: 8928571, a: 8928571.43, d: 0.0000%, tcr: 7, cpr: 1.000, div: 1 + r: 7812500, a: 7812500.00, d: 0.0000%, tcr: 8, cpr: 1.000, div: 1 + r: 4000000, a: 4000000.00, d: 0.0000%, tcr: 5, cpr: 3.125, div: 1 + r: 3686400, a: 3676470.59, d: -0.2694%, tcr: 8, cpr: 2.125, div: 1 + r: 3500000, a: 3496503.50, d: -0.0999%, tcr: 13, cpr: 1.375, div: 1 + r: 3000000, a: 2976190.48, d: -0.7937%, tcr: 14, cpr: 1.500, div: 1 + r: 2500000, a: 2500000.00, d: 0.0000%, tcr: 10, cpr: 2.500, div: 1 + r: 2000000, a: 2000000.00, d: 0.0000%, tcr: 10, cpr: 3.125, div: 1 + r: 1843200, a: 1838235.29, d: -0.2694%, tcr: 16, cpr: 2.125, div: 1 + r: 1500000, a: 1492537.31, d: -0.4975%, tcr: 5, cpr: 8.375, div: 1 + r: 1152000, a: 1152073.73, d: 0.0064%, tcr: 14, cpr: 3.875, div: 1 + r: 921600, a: 919117.65, d: -0.2694%, tcr: 16, cpr: 2.125, div: 2 + r: 576000, a: 576036.87, d: 0.0064%, tcr: 14, cpr: 3.875, div: 2 + r: 460800, a: 460829.49, d: 0.0064%, tcr: 7, cpr: 3.875, div: 5 + r: 230400, a: 230414.75, d: 0.0064%, tcr: 14, cpr: 3.875, div: 5 + r: 115200, a: 115207.37, d: 0.0064%, tcr: 14, cpr: 1.250, div: 31 + r: 57600, a: 57603.69, d: 0.0064%, tcr: 8, cpr: 3.875, div: 35 + r: 38400, a: 38402.46, d: 0.0064%, tcr: 14, cpr: 3.875, div: 30 + r: 19200, a: 19201.23, d: 0.0064%, tcr: 8, cpr: 3.875, div: 105 + r: 9600, a: 9600.06, d: 0.0006%, tcr: 9, cpr: 1.125, div: 643 + r: 4800, a: 4799.98, d: -0.0004%, tcr: 7, cpr: 2.875, div: 647 + r: 2400, a: 2400.02, d: 0.0008%, tcr: 9, cpr: 2.250, div: 1286 + r: 1200, a: 1200.00, d: 0.0000%, tcr: 14, cpr: 2.875, div: 1294 + r: 300, a: 300.00, d: 0.0000%, tcr: 11, cpr: 2.625, div: 7215 + r: 200, a: 200.00, d: 0.0000%, tcr: 16, cpr: 1.250, div: 15625 + r: 150, a: 150.00, d: 0.0000%, tcr: 13, cpr: 2.250, div: 14245 + r: 134, a: 134.00, d: 0.0000%, tcr: 11, cpr: 2.625, div: 16153 + r: 110, a: 110.00, d: 0.0000%, tcr: 12, cpr: 1.000, div: 47348 + r: 75, a: 75.00, d: 0.0000%, tcr: 4, cpr: 5.875, div: 35461 + r: 50, a: 50.00, d: 0.0000%, tcr: 16, cpr: 1.250, div: 62500 + r: 25, a: 25.00, d: 0.0000%, tcr: 16, cpr: 2.500, div: 62500 + r: 4, a: 4.00, d: 0.0000%, tcr: 16, cpr: 20.000, div: 48828 + r: 2, a: 2.00, d: 0.0000%, tcr: 16, cpr: 40.000, div: 48828 + r: 1, a: 1.00, d: 0.0000%, tcr: 16, cpr: 63.875, div: 61154 With the baud base set to 15625000 and the unsigned 16-bit UART_DIV_MAX -limitation imposed by `serial8250_get_baud_rate' standard baud rates +limitation imposed by ``serial8250_get_baud_rate`` standard baud rates below 300bps become unavailable in the regular way, e.g. the rate of 200bps requires the baud base to be divided by 78125 and that is beyond the unsigned 16-bit range. The historic spd_cust feature can still be @@ -92,15 +94,17 @@ used by encoding the values for, the pre and the clock divisor (DLM/DLL) as follows to obtain such rates if so required: - 31 29 28 20 19 16 15 0 -+-----+-----------------+-------+-------------------------------+ -|0 0 0| CPR2:CPR | TCR | DLM:DLL | -+-----+-----------------+-------+-------------------------------+ +:: -Use a value such encoded for the `custom_divisor' field along with the -ASYNC_SPD_CUST flag set in the `flags' field in `struct serial_struct' + 31 29 28 20 19 16 15 0 + +-----+-----------------+-------+-------------------------------+ + |0 0 0| CPR2:CPR | TCR | DLM:DLL | + +-----+-----------------+-------+-------------------------------+ + +Use a value such encoded for the ``custom_divisor`` field along with the +ASYNC_SPD_CUST flag set in the ``flags`` field in ``struct serial_struct`` passed with the TIOCSSERIAL ioctl(2), such as with the setserial(8) -utility and its `divisor' and `spd_cust' parameters, and the select +utility and its ``divisor`` and ``spd_cust`` parameters, and then select the baud rate of 38400bps. Note that the value of 0 in TCR sets the oversampling rate to 16 and prescaler values below 1 in CPR2/CPR are clamped by the driver to 1. @@ -111,19 +115,17 @@ the oversampling rate and the clock divi respectively. These parameters will set the baud rate for the serial port to 62500000 / 62.500 / 1250 / 16 = 50bps. -References: - -[1] "OXPCIe200 PCI Express Multi-Port Bridge", Oxford Semiconductor, - Inc., DS-0045, 10 Nov 2008, Section "950 Mode", pp. 64-65 +Maciej W. Rozycki -[2] "OXPCIe952 PCI Express Bridge to Dual Serial & Parallel Port", - Oxford Semiconductor, Inc., DS-0046, Mar 06 08, Section "950 Mode", - p. 20 +.. [OX200] "OXPCIe200 PCI Express Multi-Port Bridge", Oxford Semiconductor, + Inc., DS-0045, 10 Nov 2008, Section "950 Mode", pp. 64-65 -[3] "OXPCIe954 PCI Express Bridge to Quad Serial Port", Oxford - Semiconductor, Inc., DS-0047, Feb 08, Section "950 Mode", p. 20 +.. [OX952] "OXPCIe952 PCI Express Bridge to Dual Serial & Parallel Port", + Oxford Semiconductor, Inc., DS-0046, Mar 06 08, Section "950 Mode", + p. 20 -[4] "OXPCIe958 PCI Express Bridge to Octal Serial Port", Oxford - Semiconductor, Inc., DS-0048, Feb 08, Section "950 Mode", p. 20 +.. [OX954] "OXPCIe954 PCI Express Bridge to Quad Serial Port", Oxford + Semiconductor, Inc., DS-0047, Feb 08, Section "950 Mode", p. 20 -Maciej W. Rozycki +.. [OX958] "OXPCIe958 PCI Express Bridge to Octal Serial Port", Oxford + Semiconductor, Inc., DS-0048, Feb 08, Section "950 Mode", p. 20 From patchwork Fri May 13 22:42:13 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Maciej W. Rozycki" X-Patchwork-Id: 572767 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D5645C433EF for ; Fri, 13 May 2022 22:42:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1384836AbiEMWmV (ORCPT ); Fri, 13 May 2022 18:42:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48982 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1384840AbiEMWmQ (ORCPT ); Fri, 13 May 2022 18:42:16 -0400 Received: from angie.orcam.me.uk (angie.orcam.me.uk [IPv6:2001:4190:8020::34]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id D7C1B60D82; Fri, 13 May 2022 15:42:13 -0700 (PDT) Received: by angie.orcam.me.uk (Postfix, from userid 500) id 319889200B3; Sat, 14 May 2022 00:42:13 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by angie.orcam.me.uk (Postfix) with ESMTP id 2BB6192009B; Fri, 13 May 2022 23:42:13 +0100 (BST) Date: Fri, 13 May 2022 23:42:13 +0100 (BST) From: "Maciej W. Rozycki" To: Jonathan Corbet , Greg Kroah-Hartman , Jiri Slaby cc: Stephen Rothwell , Andy Shevchenko , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, linux-next@vger.kernel.org Subject: [PATCH 3/3] Documentation: Wire Oxford Semiconductor PCIe (Tornado) 950 In-Reply-To: Message-ID: References: User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org Wire Oxford Semiconductor PCIe (Tornado) 950 description as a chapter into the misc-devices document. Signed-off-by: Maciej W. Rozycki --- Documentation/misc-devices/index.rst | 1 + 1 file changed, 1 insertion(+) linux-doc-oxsemi-tornado-wire.diff Index: linux-macro/Documentation/misc-devices/index.rst =================================================================== --- linux-macro.orig/Documentation/misc-devices/index.rst +++ linux-macro/Documentation/misc-devices/index.rst @@ -25,6 +25,7 @@ fit into other categories. isl29003 lis3lv02d max6875 + oxsemi-tornado pci-endpoint-test spear-pcie-gadget uacce