From patchwork Mon Aug 10 14:27:42 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sakari Ailus X-Patchwork-Id: 251761 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 838B7C433E4 for ; Mon, 10 Aug 2020 14:25:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 65A172076B for ; Mon, 10 Aug 2020 14:25:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726917AbgHJOZf (ORCPT ); Mon, 10 Aug 2020 10:25:35 -0400 Received: from mga01.intel.com ([192.55.52.88]:45121 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727017AbgHJOYt (ORCPT ); Mon, 10 Aug 2020 10:24:49 -0400 IronPort-SDR: fmnMgSU1eGDFHffPoQ8Z7ySs3KSf39qQZE/m70MMsTU5K9/NL9biIjEhO8JmLovc0cfU/j/bdl pFNqzRQ6XLHA== X-IronPort-AV: E=McAfee;i="6000,8403,9708"; a="171579268" X-IronPort-AV: E=Sophos;i="5.75,457,1589266800"; d="scan'208";a="171579268" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Aug 2020 07:24:48 -0700 IronPort-SDR: YPl2fZSOAy/e24cOsyis2lgV58Q+EebSHq2FtPjmpDgwqTwRi6JPwKGv1w2wD8V5dxRmZwRLD+ gLTO5k8u7hoQ== X-IronPort-AV: E=Sophos;i="5.75,457,1589266800"; d="scan'208";a="494329333" Received: from paasikivi.fi.intel.com ([10.237.72.42]) by fmsmga006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Aug 2020 07:24:44 -0700 Received: from punajuuri.localdomain (punajuuri.localdomain [192.168.240.130]) by paasikivi.fi.intel.com (Postfix) with ESMTP id 9EABA2056B; Mon, 10 Aug 2020 17:24:41 +0300 (EEST) Received: from sailus by punajuuri.localdomain with local (Exim 4.92) (envelope-from ) id 1k58mC-0003Er-5a; Mon, 10 Aug 2020 17:27:48 +0300 From: Sakari Ailus To: linux-i2c@vger.kernel.org Cc: Wolfram Sang , "Rafael J. Wysocki" , linux-acpi@vger.kernel.org, Bingbu Cao , linux-media@vger.kernel.org, Chiranjeevi Rapolu , Hyungwoo Yang , Bartosz Golaszewski , Arnd Bergmann , linux-kernel@vger.kernel.org, Greg Kroah-Hartman , rajmohan.mani@intel.com, Tomasz Figa , "Qiu, Tian Shu" Subject: [PATCH v5 1/6] i2c: Allow driver to manage the device's power state during probe Date: Mon, 10 Aug 2020 17:27:42 +0300 Message-Id: <20200810142747.12400-2-sakari.ailus@linux.intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200810142747.12400-1-sakari.ailus@linux.intel.com> References: <20200810142747.12400-1-sakari.ailus@linux.intel.com> MIME-Version: 1.0 Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org Enable drivers to tell ACPI that there's no need to power on a device for probe. Drivers should still perform this by themselves if there's a need to. In some cases powering on the device during probe is undesirable, and this change enables a driver to choose what fits best for it. Add a field called "flags" into struct i2c_driver for driver flags, and a flag I2C_DRV_FL_ALLOW_LOW_POWER_PROBE to tell a driver supports probe in low power state. Signed-off-by: Sakari Ailus --- drivers/i2c/i2c-core-base.c | 17 ++++++++++++++--- include/linux/i2c.h | 14 ++++++++++++++ 2 files changed, 28 insertions(+), 3 deletions(-) diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c index 34a9609f256da..cde9cf49a07e6 100644 --- a/drivers/i2c/i2c-core-base.c +++ b/drivers/i2c/i2c-core-base.c @@ -436,6 +436,14 @@ static int i2c_smbus_host_notify_to_irq(const struct i2c_client *client) return irq > 0 ? irq : -ENXIO; } +static bool allow_low_power_probe(struct device *dev) +{ + struct i2c_driver *driver = to_i2c_driver(dev->driver); + + return driver->flags & I2C_DRV_FL_ALLOW_LOW_POWER_PROBE && + device_property_present(dev, "allow-low-power-probe"); +} + static int i2c_device_probe(struct device *dev) { struct i2c_client *client = i2c_verify_client(dev); @@ -514,7 +522,8 @@ static int i2c_device_probe(struct device *dev) if (status < 0) goto err_clear_wakeup_irq; - status = dev_pm_domain_attach(&client->dev, true); + status = dev_pm_domain_attach(&client->dev, + !allow_low_power_probe(&client->dev)); if (status) goto err_clear_wakeup_irq; @@ -536,7 +545,8 @@ static int i2c_device_probe(struct device *dev) return 0; err_detach_pm_domain: - dev_pm_domain_detach(&client->dev, true); + dev_pm_domain_detach(&client->dev, + !allow_low_power_probe(&client->dev)); err_clear_wakeup_irq: dev_pm_clear_wake_irq(&client->dev); device_init_wakeup(&client->dev, false); @@ -562,7 +572,8 @@ static int i2c_device_remove(struct device *dev) status = driver->remove(client); } - dev_pm_domain_detach(&client->dev, true); + dev_pm_domain_detach(&client->dev, + !allow_low_power_probe(&client->dev)); dev_pm_clear_wake_irq(&client->dev); device_init_wakeup(&client->dev, false); diff --git a/include/linux/i2c.h b/include/linux/i2c.h index fc55ea41d3237..6824719c24ebe 100644 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -11,6 +11,7 @@ #define _LINUX_I2C_H #include /* for acpi_handle */ +#include #include #include /* for struct device */ #include /* for completion */ @@ -217,6 +218,16 @@ enum i2c_alert_protocol { I2C_PROTOCOL_SMBUS_HOST_NOTIFY, }; +/** + * enum i2c_driver_flags - Flags for an I2C device driver + * + * @I2C_DRV_FL_ALLOW_LOW_POWER_PROBE: Let the driver manage the device's power + * state during probe and remove + */ +enum i2c_driver_flags { + I2C_DRV_FL_ALLOW_LOW_POWER_PROBE = BIT(0), +}; + /** * struct i2c_driver - represent an I2C device driver * @class: What kind of i2c device we instantiate (for detect) @@ -231,6 +242,7 @@ enum i2c_alert_protocol { * @detect: Callback for device detection * @address_list: The I2C addresses to probe (for detect) * @clients: List of detected clients we created (for i2c-core use only) + * @flags: A bitmask of flags defined in &enum i2c_driver_flags * * The driver.owner field should be set to the module owner of this driver. * The driver.name field should be set to the name of this driver. @@ -289,6 +301,8 @@ struct i2c_driver { int (*detect)(struct i2c_client *client, struct i2c_board_info *info); const unsigned short *address_list; struct list_head clients; + + unsigned int flags; }; #define to_i2c_driver(d) container_of(d, struct i2c_driver, driver) From patchwork Mon Aug 10 14:27:44 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sakari Ailus X-Patchwork-Id: 251763 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 13FC9C433E0 for ; Mon, 10 Aug 2020 14:24:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E930E2070B for ; Mon, 10 Aug 2020 14:24:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726917AbgHJOYs (ORCPT ); Mon, 10 Aug 2020 10:24:48 -0400 Received: from mga04.intel.com ([192.55.52.120]:28442 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726910AbgHJOYs (ORCPT ); Mon, 10 Aug 2020 10:24:48 -0400 IronPort-SDR: sB39yN+BVDu2PoWjFb+GvvuwE1xCzGOF9zhlrYpHtajDLw82dcwzNdyBRKMi1WHilBONsBlZaQ ft10DzkhgKjw== X-IronPort-AV: E=McAfee;i="6000,8403,9708"; a="150973817" X-IronPort-AV: E=Sophos;i="5.75,457,1589266800"; d="scan'208";a="150973817" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Aug 2020 07:24:46 -0700 IronPort-SDR: 6faF++bStC7CbW7JmF76TSaiiQB8K0ag+qY7CtjTExBsoF8Z8QYg8tL18A5c35oN0yfmKcaQeX o5OJad2qHQyQ== X-IronPort-AV: E=Sophos;i="5.75,457,1589266800"; d="scan'208";a="308086172" Received: from paasikivi.fi.intel.com ([10.237.72.42]) by orsmga002-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Aug 2020 07:24:43 -0700 Received: from punajuuri.localdomain (punajuuri.localdomain [192.168.240.130]) by paasikivi.fi.intel.com (Postfix) with ESMTP id ACC8F209D1; Mon, 10 Aug 2020 17:24:41 +0300 (EEST) Received: from sailus by punajuuri.localdomain with local (Exim 4.92) (envelope-from ) id 1k58mC-0003Ex-88; Mon, 10 Aug 2020 17:27:48 +0300 From: Sakari Ailus To: linux-i2c@vger.kernel.org Cc: Wolfram Sang , "Rafael J. Wysocki" , linux-acpi@vger.kernel.org, Bingbu Cao , linux-media@vger.kernel.org, Chiranjeevi Rapolu , Hyungwoo Yang , Bartosz Golaszewski , Arnd Bergmann , linux-kernel@vger.kernel.org, Greg Kroah-Hartman , rajmohan.mani@intel.com, Tomasz Figa , "Qiu, Tian Shu" Subject: [PATCH v5 3/6] ov5670: Support probe whilst the device is in a low power state Date: Mon, 10 Aug 2020 17:27:44 +0300 Message-Id: <20200810142747.12400-4-sakari.ailus@linux.intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200810142747.12400-1-sakari.ailus@linux.intel.com> References: <20200810142747.12400-1-sakari.ailus@linux.intel.com> MIME-Version: 1.0 Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org Tell ACPI device PM code that the driver supports the device being in a low power state when the driver's probe function is entered. Signed-off-by: Sakari Ailus --- drivers/media/i2c/ov5670.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-) diff --git a/drivers/media/i2c/ov5670.c b/drivers/media/i2c/ov5670.c index f26252e35e08d..1f75b888d2a18 100644 --- a/drivers/media/i2c/ov5670.c +++ b/drivers/media/i2c/ov5670.c @@ -2456,6 +2456,7 @@ static int ov5670_probe(struct i2c_client *client) struct ov5670 *ov5670; const char *err_msg; u32 input_clk = 0; + bool low_power; int ret; device_property_read_u32(&client->dev, "clock-frequency", &input_clk); @@ -2472,11 +2473,14 @@ static int ov5670_probe(struct i2c_client *client) /* Initialize subdev */ v4l2_i2c_subdev_init(&ov5670->sd, client, &ov5670_subdev_ops); - /* Check module identity */ - ret = ov5670_identify_module(ov5670); - if (ret) { - err_msg = "ov5670_identify_module() error"; - goto error_print; + low_power = acpi_dev_state_low_power(&client->dev); + if (!low_power) { + /* Check module identity */ + ret = ov5670_identify_module(ov5670); + if (ret) { + err_msg = "ov5670_identify_module() error"; + goto error_print; + } } mutex_init(&ov5670->mutex); @@ -2513,10 +2517,10 @@ static int ov5670_probe(struct i2c_client *client) ov5670->streaming = false; /* - * Device is already turned on by i2c-core with ACPI domain PM. - * Enable runtime PM and turn off the device. + * Don't set the device's state to active if it's in a low power state. */ - pm_runtime_set_active(&client->dev); + if (!low_power) + pm_runtime_set_active(&client->dev); pm_runtime_enable(&client->dev); pm_runtime_idle(&client->dev); @@ -2558,7 +2562,7 @@ static const struct dev_pm_ops ov5670_pm_ops = { #ifdef CONFIG_ACPI static const struct acpi_device_id ov5670_acpi_ids[] = { - {"INT3479"}, + { "INT3479" }, { /* sentinel */ } }; @@ -2573,6 +2577,7 @@ static struct i2c_driver ov5670_i2c_driver = { }, .probe_new = ov5670_probe, .remove = ov5670_remove, + .flags = I2C_DRV_FL_ALLOW_LOW_POWER_PROBE, }; module_i2c_driver(ov5670_i2c_driver); From patchwork Mon Aug 10 14:27:45 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sakari Ailus X-Patchwork-Id: 251760 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 52DB8C433DF for ; Mon, 10 Aug 2020 14:25:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2BFC42076B for ; Mon, 10 Aug 2020 14:25:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726955AbgHJOYs (ORCPT ); Mon, 10 Aug 2020 10:24:48 -0400 Received: from mga05.intel.com ([192.55.52.43]:5304 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726897AbgHJOYs (ORCPT ); Mon, 10 Aug 2020 10:24:48 -0400 IronPort-SDR: W6DyI0fS2XxlYkJaglwXzF7uqVXGVze2ajKL6b8rklgjoaAlORi+dxr6jEgAkpZVSAK5gcdMNk UYl6+JFqcQcw== X-IronPort-AV: E=McAfee;i="6000,8403,9708"; a="238371926" X-IronPort-AV: E=Sophos;i="5.75,457,1589266800"; d="scan'208";a="238371926" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Aug 2020 07:24:46 -0700 IronPort-SDR: 52m5sVXupHSldNjkls906YBK8xA0kbrQeZ5AX59IHpMo+rS4hYsYQRa2rKzREw1s9Lushq1iYD pAD0Y7os7POQ== X-IronPort-AV: E=Sophos;i="5.75,457,1589266800"; d="scan'208";a="277292106" Received: from paasikivi.fi.intel.com ([10.237.72.42]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Aug 2020 07:24:43 -0700 Received: from punajuuri.localdomain (punajuuri.localdomain [192.168.240.130]) by paasikivi.fi.intel.com (Postfix) with ESMTP id B48DF20AC3; Mon, 10 Aug 2020 17:24:41 +0300 (EEST) Received: from sailus by punajuuri.localdomain with local (Exim 4.92) (envelope-from ) id 1k58mC-0003F0-9I; Mon, 10 Aug 2020 17:27:48 +0300 From: Sakari Ailus To: linux-i2c@vger.kernel.org Cc: Wolfram Sang , "Rafael J. Wysocki" , linux-acpi@vger.kernel.org, Bingbu Cao , linux-media@vger.kernel.org, Chiranjeevi Rapolu , Hyungwoo Yang , Bartosz Golaszewski , Arnd Bergmann , linux-kernel@vger.kernel.org, Greg Kroah-Hartman , rajmohan.mani@intel.com, Tomasz Figa , "Qiu, Tian Shu" Subject: [PATCH v5 4/6] media: i2c: imx319: Support probe while the device is off Date: Mon, 10 Aug 2020 17:27:45 +0300 Message-Id: <20200810142747.12400-5-sakari.ailus@linux.intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200810142747.12400-1-sakari.ailus@linux.intel.com> References: <20200810142747.12400-1-sakari.ailus@linux.intel.com> MIME-Version: 1.0 Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org From: Rajmohan Mani Tell ACPI device PM code that the driver supports the device being powered off when the driver's probe function is entered. Signed-off-by: Rajmohan Mani Signed-off-by: Sakari Ailus --- drivers/media/i2c/imx319.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-) diff --git a/drivers/media/i2c/imx319.c b/drivers/media/i2c/imx319.c index 17c2e4b41221e..dc5ebff6a85a3 100644 --- a/drivers/media/i2c/imx319.c +++ b/drivers/media/i2c/imx319.c @@ -2424,6 +2424,7 @@ static struct imx319_hwcfg *imx319_get_hwcfg(struct device *dev) static int imx319_probe(struct i2c_client *client) { struct imx319 *imx319; + bool low_power; int ret; u32 i; @@ -2436,11 +2437,14 @@ static int imx319_probe(struct i2c_client *client) /* Initialize subdev */ v4l2_i2c_subdev_init(&imx319->sd, client, &imx319_subdev_ops); - /* Check module identity */ - ret = imx319_identify_module(imx319); - if (ret) { - dev_err(&client->dev, "failed to find sensor: %d", ret); - goto error_probe; + low_power = acpi_dev_state_low_power(&client->dev); + if (!low_power) { + /* Check module identity */ + ret = imx319_identify_module(imx319); + if (ret) { + dev_err(&client->dev, "failed to find sensor: %d", ret); + goto error_probe; + } } imx319->hwcfg = imx319_get_hwcfg(&client->dev); @@ -2493,10 +2497,10 @@ static int imx319_probe(struct i2c_client *client) goto error_media_entity; /* - * Device is already turned on by i2c-core with ACPI domain PM. - * Enable runtime PM and turn off the device. + * Don't set the device's state to active if it's in a low power state. */ - pm_runtime_set_active(&client->dev); + if (!low_power) + pm_runtime_set_active(&client->dev); pm_runtime_enable(&client->dev); pm_runtime_idle(&client->dev); @@ -2536,7 +2540,7 @@ static const struct dev_pm_ops imx319_pm_ops = { }; static const struct acpi_device_id imx319_acpi_ids[] = { - { "SONY319A" }, + { "SONY319A", }, { /* sentinel */ } }; MODULE_DEVICE_TABLE(acpi, imx319_acpi_ids); @@ -2549,6 +2553,7 @@ static struct i2c_driver imx319_i2c_driver = { }, .probe_new = imx319_probe, .remove = imx319_remove, + .flags = I2C_DRV_FL_ALLOW_LOW_POWER_PROBE, }; module_i2c_driver(imx319_i2c_driver); From patchwork Mon Aug 10 14:27:47 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Sakari Ailus X-Patchwork-Id: 251762 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 71CD1C433DF for ; Mon, 10 Aug 2020 14:25:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 51E192070B for ; Mon, 10 Aug 2020 14:25:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727079AbgHJOY4 (ORCPT ); Mon, 10 Aug 2020 10:24:56 -0400 Received: from mga18.intel.com ([134.134.136.126]:26240 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727061AbgHJOYy (ORCPT ); Mon, 10 Aug 2020 10:24:54 -0400 IronPort-SDR: qNzIV5FkwiWh+2U9XevxgSWdLP6YZABwDHEN3kBcQWu3dZ5erAooH2CPBtfMElTI2d09phIRC9 fL0d+RyY4wWQ== X-IronPort-AV: E=McAfee;i="6000,8403,9708"; a="141147154" X-IronPort-AV: E=Sophos;i="5.75,457,1589266800"; d="scan'208";a="141147154" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Aug 2020 07:24:53 -0700 IronPort-SDR: Cbfr4X4RiO57NQGiwjxsRxZOEYXtBlVUul/a9/rIV2xjPCkEFWfkezRP9cFsrssD2MtUuN/m2C 21rbVghlHELg== X-IronPort-AV: E=Sophos;i="5.75,457,1589266800"; d="scan'208";a="438711300" Received: from paasikivi.fi.intel.com ([10.237.72.42]) by orsmga004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Aug 2020 07:24:49 -0700 Received: from punajuuri.localdomain (punajuuri.localdomain [192.168.240.130]) by paasikivi.fi.intel.com (Postfix) with ESMTP id C9A4720BC0; Mon, 10 Aug 2020 17:24:41 +0300 (EEST) Received: from sailus by punajuuri.localdomain with local (Exim 4.92) (envelope-from ) id 1k58mC-0003F6-Bp; Mon, 10 Aug 2020 17:27:48 +0300 From: Sakari Ailus To: linux-i2c@vger.kernel.org Cc: Wolfram Sang , "Rafael J. Wysocki" , linux-acpi@vger.kernel.org, Bingbu Cao , linux-media@vger.kernel.org, Chiranjeevi Rapolu , Hyungwoo Yang , Bartosz Golaszewski , Arnd Bergmann , linux-kernel@vger.kernel.org, Greg Kroah-Hartman , rajmohan.mani@intel.com, Tomasz Figa , "Qiu, Tian Shu" Subject: [PATCH v5 6/6] Documentation: ACPI: Document allow-low-power-probe _DSD property Date: Mon, 10 Aug 2020 17:27:47 +0300 Message-Id: <20200810142747.12400-7-sakari.ailus@linux.intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200810142747.12400-1-sakari.ailus@linux.intel.com> References: <20200810142747.12400-1-sakari.ailus@linux.intel.com> MIME-Version: 1.0 Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org Document the probe-low-power _DSD property and how it is used with I²C drivers. Signed-off-by: Sakari Ailus --- .../acpi/dsd/allow-low-power-probe.rst | 28 +++++++++++++++++++ Documentation/firmware-guide/acpi/index.rst | 1 + 2 files changed, 29 insertions(+) create mode 100644 Documentation/firmware-guide/acpi/dsd/allow-low-power-probe.rst diff --git a/Documentation/firmware-guide/acpi/dsd/allow-low-power-probe.rst b/Documentation/firmware-guide/acpi/dsd/allow-low-power-probe.rst new file mode 100644 index 0000000000000..6fcc89162b898 --- /dev/null +++ b/Documentation/firmware-guide/acpi/dsd/allow-low-power-probe.rst @@ -0,0 +1,28 @@ +.. SPDX-License-Identifier: GPL-2.0 + +====================================== +Probing I²C devices in low power state +====================================== + +Introduction +============ + +In some cases it may be preferred to leave certain devices powered off for the +entire system bootup if powering on these devices has adverse side effects, +beyond just powering on the said device. Linux recognizes the _DSD property +"allow-low-power-probe" that can be used for this purpose. + +How it works +============ + +The property "allow-low-power-probe" boolean property may be used to tell Linux +that the I²C framework should instruct the kernel ACPI framework to leave the +device in the low power state. If the driver indicates its support for this by +setting the I2C_DRV_FL_ALLOW_LOW_POWER_PROBE flag in struct i2c_driver.flags +field and the "allow-low-power-probe" property is present, the device will not +be powered on for probe. + +The downside is that as the device is not powered on, even if there's a problem +with the device, the driver likely probes just fine but the first user will +find out the device doesn't work, instead of a failure at probe time. This +feature should thus be used sparingly. diff --git a/Documentation/firmware-guide/acpi/index.rst b/Documentation/firmware-guide/acpi/index.rst index ad3b5afdae77e..0070fcde9e669 100644 --- a/Documentation/firmware-guide/acpi/index.rst +++ b/Documentation/firmware-guide/acpi/index.rst @@ -11,6 +11,7 @@ ACPI Support dsd/graph dsd/data-node-references dsd/leds + dsd/allow-low-power-probe enumeration osi method-customizing