| Message ID | 20240906225435.707837-1-florian.fainelli@broadcom.com |
|---|---|
| State | New |
| Headers | show |
| Series | tty: rp2: Fix reset with non forgiving PCIe host bridges | expand |
On Fri, Sep 06, 2024 at 03:54:33PM -0700, Florian Fainelli wrote: > The write to RP2_GLOBAL_CMD followed by an immediate read of > RP2_GLOBAL_CMD in rp2_reset_asic() is intented to flush out the write, > however by then the device is already in reset and cannot respond to a > memory cycle access. > > On platforms such as the Raspberry Pi 4 and others using the > pcie-brcmstb.c driver, any memory access to a device that cannot respond > is met with a fatal system error, rather than being substituted with all > 1s as is usually the case on PC platforms. > > Swapping the delay and the read ensures that the device has finished > resetting before we attempt to read from it. > > Fixes: 7d9f49afa451 ("serial: rp2: New driver for Comtrol RocketPort 2 cards") > Suggested-by: Jim Quinlan <james.quinlan@broadcom.com> > Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com> > --- > drivers/tty/serial/rp2.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) Hi, This is the friendly patch-bot of Greg Kroah-Hartman. You have sent him a patch that has triggered this response. He used to manually respond to these common problems, but in order to save his sanity (he kept writing the same thing over and over, yet to different people), I was created. Hopefully you will not take offence and will fix the problem in your patch and resubmit it so that it can be accepted into the Linux kernel tree. You are receiving this message because of the following common error(s) as indicated below: - You have marked a patch with a "Fixes:" tag for a commit that is in an older released kernel, yet you do not have a cc: stable line in the signed-off-by area at all, which means that the patch will not be applied to any older kernel releases. To properly fix this, please follow the documented rules in the Documentation/process/stable-kernel-rules.rst file for how to resolve this. If you wish to discuss this problem further, or you have questions about how to resolve this issue, please feel free to respond to this email and Greg will reply once he has dug out from the pending patches received from other developers. thanks, greg k-h's patch email bot
On Fri, Sep 6, 2024 at 6:54 PM Florian Fainelli <florian.fainelli@broadcom.com> wrote: > > The write to RP2_GLOBAL_CMD followed by an immediate read of > RP2_GLOBAL_CMD in rp2_reset_asic() is intented to flush out the write, > however by then the device is already in reset and cannot respond to a > memory cycle access. > > On platforms such as the Raspberry Pi 4 and others using the > pcie-brcmstb.c driver, any memory access to a device that cannot respond > is met with a fatal system error, rather than being substituted with all > 1s as is usually the case on PC platforms. > > Swapping the delay and the read ensures that the device has finished > resetting before we attempt to read from it. > > Fixes: 7d9f49afa451 ("serial: rp2: New driver for Comtrol RocketPort 2 cards") > Suggested-by: Jim Quinlan <james.quinlan@broadcom.com> > Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com> > --- > drivers/tty/serial/rp2.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/tty/serial/rp2.c b/drivers/tty/serial/rp2.c > index 4132fcff7d4e..8bab2aedc499 100644 > --- a/drivers/tty/serial/rp2.c > +++ b/drivers/tty/serial/rp2.c > @@ -577,8 +577,8 @@ static void rp2_reset_asic(struct rp2_card *card, unsigned int asic_id) > u32 clk_cfg; > > writew(1, base + RP2_GLOBAL_CMD); > - readw(base + RP2_GLOBAL_CMD); > msleep(100); > + readw(base + RP2_GLOBAL_CMD); Since the assumed purpose of the readw() was to flush the writew(), would it make sense to add a barrier after the writew()? Regards, Jim Quinlan Broadcom STB/CM > writel(0, base + RP2_CLK_PRESCALER); > > /* TDM clock configuration */ > -- > 2.43.0 >
On 9/11/24 14:47, Jim Quinlan wrote: > On Fri, Sep 6, 2024 at 6:54 PM Florian Fainelli > <florian.fainelli@broadcom.com> wrote: >> >> The write to RP2_GLOBAL_CMD followed by an immediate read of >> RP2_GLOBAL_CMD in rp2_reset_asic() is intented to flush out the write, >> however by then the device is already in reset and cannot respond to a >> memory cycle access. >> >> On platforms such as the Raspberry Pi 4 and others using the >> pcie-brcmstb.c driver, any memory access to a device that cannot respond >> is met with a fatal system error, rather than being substituted with all >> 1s as is usually the case on PC platforms. >> >> Swapping the delay and the read ensures that the device has finished >> resetting before we attempt to read from it. >> >> Fixes: 7d9f49afa451 ("serial: rp2: New driver for Comtrol RocketPort 2 cards") >> Suggested-by: Jim Quinlan <james.quinlan@broadcom.com> >> Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com> >> --- >> drivers/tty/serial/rp2.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/tty/serial/rp2.c b/drivers/tty/serial/rp2.c >> index 4132fcff7d4e..8bab2aedc499 100644 >> --- a/drivers/tty/serial/rp2.c >> +++ b/drivers/tty/serial/rp2.c >> @@ -577,8 +577,8 @@ static void rp2_reset_asic(struct rp2_card *card, unsigned int asic_id) >> u32 clk_cfg; >> >> writew(1, base + RP2_GLOBAL_CMD); >> - readw(base + RP2_GLOBAL_CMD); >> msleep(100); >> + readw(base + RP2_GLOBAL_CMD); > > Since the assumed purpose of the readw() was to flush the writew(), > would it make sense to add a barrier after the writew()? AFAICT there is one which is implied within the name, as it is not a _relaxed() variant. Did you mean a different sort of barrier to be used?
On Wed, Sep 11, 2024 at 6:01 PM Florian Fainelli <florian.fainelli@broadcom.com> wrote: > > On 9/11/24 14:47, Jim Quinlan wrote: > > On Fri, Sep 6, 2024 at 6:54 PM Florian Fainelli > > <florian.fainelli@broadcom.com> wrote: > >> > >> The write to RP2_GLOBAL_CMD followed by an immediate read of > >> RP2_GLOBAL_CMD in rp2_reset_asic() is intented to flush out the write, > >> however by then the device is already in reset and cannot respond to a > >> memory cycle access. > >> > >> On platforms such as the Raspberry Pi 4 and others using the > >> pcie-brcmstb.c driver, any memory access to a device that cannot respond > >> is met with a fatal system error, rather than being substituted with all > >> 1s as is usually the case on PC platforms. > >> > >> Swapping the delay and the read ensures that the device has finished > >> resetting before we attempt to read from it. > >> > >> Fixes: 7d9f49afa451 ("serial: rp2: New driver for Comtrol RocketPort 2 cards") > >> Suggested-by: Jim Quinlan <james.quinlan@broadcom.com> > >> Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com> > >> --- > >> drivers/tty/serial/rp2.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/drivers/tty/serial/rp2.c b/drivers/tty/serial/rp2.c > >> index 4132fcff7d4e..8bab2aedc499 100644 > >> --- a/drivers/tty/serial/rp2.c > >> +++ b/drivers/tty/serial/rp2.c > >> @@ -577,8 +577,8 @@ static void rp2_reset_asic(struct rp2_card *card, unsigned int asic_id) > >> u32 clk_cfg; > >> > >> writew(1, base + RP2_GLOBAL_CMD); > >> - readw(base + RP2_GLOBAL_CMD); > >> msleep(100); > >> + readw(base + RP2_GLOBAL_CMD); > > > > Since the assumed purpose of the readw() was to flush the writew(), > > would it make sense to add a barrier after the writew()? > > AFAICT there is one which is implied within the name, as it is not a > _relaxed() variant. Did you mean a different sort of barrier to be used? Not sure. The __raw_writew() is followed by __io_aw(), which is a no-op on arm64. I don't know arm64 well enough to know if a follow-up barrier is needed. - Jim > -- > Florian >
On 9/11/24 15:16, Jim Quinlan wrote: > On Wed, Sep 11, 2024 at 6:01 PM Florian Fainelli > <florian.fainelli@broadcom.com> wrote: >> >> On 9/11/24 14:47, Jim Quinlan wrote: >>> On Fri, Sep 6, 2024 at 6:54 PM Florian Fainelli >>> <florian.fainelli@broadcom.com> wrote: >>>> >>>> The write to RP2_GLOBAL_CMD followed by an immediate read of >>>> RP2_GLOBAL_CMD in rp2_reset_asic() is intented to flush out the write, >>>> however by then the device is already in reset and cannot respond to a >>>> memory cycle access. >>>> >>>> On platforms such as the Raspberry Pi 4 and others using the >>>> pcie-brcmstb.c driver, any memory access to a device that cannot respond >>>> is met with a fatal system error, rather than being substituted with all >>>> 1s as is usually the case on PC platforms. >>>> >>>> Swapping the delay and the read ensures that the device has finished >>>> resetting before we attempt to read from it. >>>> >>>> Fixes: 7d9f49afa451 ("serial: rp2: New driver for Comtrol RocketPort 2 cards") >>>> Suggested-by: Jim Quinlan <james.quinlan@broadcom.com> >>>> Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com> >>>> --- >>>> drivers/tty/serial/rp2.c | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/tty/serial/rp2.c b/drivers/tty/serial/rp2.c >>>> index 4132fcff7d4e..8bab2aedc499 100644 >>>> --- a/drivers/tty/serial/rp2.c >>>> +++ b/drivers/tty/serial/rp2.c >>>> @@ -577,8 +577,8 @@ static void rp2_reset_asic(struct rp2_card *card, unsigned int asic_id) >>>> u32 clk_cfg; >>>> >>>> writew(1, base + RP2_GLOBAL_CMD); >>>> - readw(base + RP2_GLOBAL_CMD); >>>> msleep(100); >>>> + readw(base + RP2_GLOBAL_CMD); >>> >>> Since the assumed purpose of the readw() was to flush the writew(), >>> would it make sense to add a barrier after the writew()? >> >> AFAICT there is one which is implied within the name, as it is not a >> _relaxed() variant. Did you mean a different sort of barrier to be used? > > Not sure. The __raw_writew() is followed by __io_aw(), which is a > no-op on arm64. I don't know arm64 well enough to know if a follow-up > barrier is needed. By definition all of the {read,write}{b,w,l,q} do include an adequate barrier and perform the adequate endian swapping since they originated from PCI drivers on x86. If you do not want any barrier you would have to use the _relaxed variants, or if you want native ordering, you would use the __raw_* variant.
On Wed, Sep 11, 2024 at 6:19 PM Florian Fainelli <florian.fainelli@broadcom.com> wrote: > > On 9/11/24 15:16, Jim Quinlan wrote: > > On Wed, Sep 11, 2024 at 6:01 PM Florian Fainelli > > <florian.fainelli@broadcom.com> wrote: > >> > >> On 9/11/24 14:47, Jim Quinlan wrote: > >>> On Fri, Sep 6, 2024 at 6:54 PM Florian Fainelli > >>> <florian.fainelli@broadcom.com> wrote: > >>>> > >>>> The write to RP2_GLOBAL_CMD followed by an immediate read of > >>>> RP2_GLOBAL_CMD in rp2_reset_asic() is intented to flush out the write, > >>>> however by then the device is already in reset and cannot respond to a > >>>> memory cycle access. > >>>> > >>>> On platforms such as the Raspberry Pi 4 and others using the > >>>> pcie-brcmstb.c driver, any memory access to a device that cannot respond > >>>> is met with a fatal system error, rather than being substituted with all > >>>> 1s as is usually the case on PC platforms. > >>>> > >>>> Swapping the delay and the read ensures that the device has finished > >>>> resetting before we attempt to read from it. > >>>> > >>>> Fixes: 7d9f49afa451 ("serial: rp2: New driver for Comtrol RocketPort 2 cards") > >>>> Suggested-by: Jim Quinlan <james.quinlan@broadcom.com> > >>>> Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com> > >>>> --- > >>>> drivers/tty/serial/rp2.c | 2 +- > >>>> 1 file changed, 1 insertion(+), 1 deletion(-) > >>>> > >>>> diff --git a/drivers/tty/serial/rp2.c b/drivers/tty/serial/rp2.c > >>>> index 4132fcff7d4e..8bab2aedc499 100644 > >>>> --- a/drivers/tty/serial/rp2.c > >>>> +++ b/drivers/tty/serial/rp2.c > >>>> @@ -577,8 +577,8 @@ static void rp2_reset_asic(struct rp2_card *card, unsigned int asic_id) > >>>> u32 clk_cfg; > >>>> > >>>> writew(1, base + RP2_GLOBAL_CMD); > >>>> - readw(base + RP2_GLOBAL_CMD); > >>>> msleep(100); > >>>> + readw(base + RP2_GLOBAL_CMD); > >>> > >>> Since the assumed purpose of the readw() was to flush the writew(), > >>> would it make sense to add a barrier after the writew()? > >> > >> AFAICT there is one which is implied within the name, as it is not a > >> _relaxed() variant. Did you mean a different sort of barrier to be used? > > > > Not sure. The __raw_writew() is followed by __io_aw(), which is a > > no-op on arm64. I don't know arm64 well enough to know if a follow-up > > barrier is needed. > > By definition all of the {read,write}{b,w,l,q} do include an adequate > barrier I do see this in the kernel, e.g. altera_edac.c, pci-hyperv.c, oxu210hp-hcd.c, etc: write[lw](..); wmb(); All I am saying is that the definition of writew() for arm64 has no explicit barrier *after* it makes the __raw_writew() call, since its __io_aw() call is a no-op. I really don't know if this matters, just wanted to mention it. Regards, Jim and perform the adequate endian swapping since they originated > from PCI drivers on x86. If you do not want any barrier you would have > to use the _relaxed variants, or if you want native ordering, you would > use the __raw_* variant. > -- > Florian
On 9/11/24 15:44, Jim Quinlan wrote: > On Wed, Sep 11, 2024 at 6:19 PM Florian Fainelli > <florian.fainelli@broadcom.com> wrote: >> >> On 9/11/24 15:16, Jim Quinlan wrote: >>> On Wed, Sep 11, 2024 at 6:01 PM Florian Fainelli >>> <florian.fainelli@broadcom.com> wrote: >>>> >>>> On 9/11/24 14:47, Jim Quinlan wrote: >>>>> On Fri, Sep 6, 2024 at 6:54 PM Florian Fainelli >>>>> <florian.fainelli@broadcom.com> wrote: >>>>>> >>>>>> The write to RP2_GLOBAL_CMD followed by an immediate read of >>>>>> RP2_GLOBAL_CMD in rp2_reset_asic() is intented to flush out the write, >>>>>> however by then the device is already in reset and cannot respond to a >>>>>> memory cycle access. >>>>>> >>>>>> On platforms such as the Raspberry Pi 4 and others using the >>>>>> pcie-brcmstb.c driver, any memory access to a device that cannot respond >>>>>> is met with a fatal system error, rather than being substituted with all >>>>>> 1s as is usually the case on PC platforms. >>>>>> >>>>>> Swapping the delay and the read ensures that the device has finished >>>>>> resetting before we attempt to read from it. >>>>>> >>>>>> Fixes: 7d9f49afa451 ("serial: rp2: New driver for Comtrol RocketPort 2 cards") >>>>>> Suggested-by: Jim Quinlan <james.quinlan@broadcom.com> >>>>>> Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com> >>>>>> --- >>>>>> drivers/tty/serial/rp2.c | 2 +- >>>>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>>>> >>>>>> diff --git a/drivers/tty/serial/rp2.c b/drivers/tty/serial/rp2.c >>>>>> index 4132fcff7d4e..8bab2aedc499 100644 >>>>>> --- a/drivers/tty/serial/rp2.c >>>>>> +++ b/drivers/tty/serial/rp2.c >>>>>> @@ -577,8 +577,8 @@ static void rp2_reset_asic(struct rp2_card *card, unsigned int asic_id) >>>>>> u32 clk_cfg; >>>>>> >>>>>> writew(1, base + RP2_GLOBAL_CMD); >>>>>> - readw(base + RP2_GLOBAL_CMD); >>>>>> msleep(100); >>>>>> + readw(base + RP2_GLOBAL_CMD); >>>>> >>>>> Since the assumed purpose of the readw() was to flush the writew(), >>>>> would it make sense to add a barrier after the writew()? >>>> >>>> AFAICT there is one which is implied within the name, as it is not a >>>> _relaxed() variant. Did you mean a different sort of barrier to be used? >>> >>> Not sure. The __raw_writew() is followed by __io_aw(), which is a >>> no-op on arm64. I don't know arm64 well enough to know if a follow-up >>> barrier is needed. >> >> By definition all of the {read,write}{b,w,l,q} do include an adequate >> barrier > I do see this in the kernel, e.g. altera_edac.c, pci-hyperv.c, > oxu210hp-hcd.c, etc: > > write[lw](..); > wmb(); > > All I am saying is that the definition of writew() for arm64 has no > explicit barrier *after* it makes the __raw_writew() call, since its > __io_aw() call is a no-op. I really don't know if this matters, just > wanted to mention it. Not having the documentation for this peripheral, not sure TBH. As far as the drivers you quoted given the __io_bw() does include a barrier, it would appear that the barrier after is possibly redundant, or is based upon a misunderstanding of which side of the write the barrier must be on, or maybe they are actually necessary, but undocumented as such..
diff --git a/drivers/tty/serial/rp2.c b/drivers/tty/serial/rp2.c index 4132fcff7d4e..8bab2aedc499 100644 --- a/drivers/tty/serial/rp2.c +++ b/drivers/tty/serial/rp2.c @@ -577,8 +577,8 @@ static void rp2_reset_asic(struct rp2_card *card, unsigned int asic_id) u32 clk_cfg; writew(1, base + RP2_GLOBAL_CMD); - readw(base + RP2_GLOBAL_CMD); msleep(100); + readw(base + RP2_GLOBAL_CMD); writel(0, base + RP2_CLK_PRESCALER); /* TDM clock configuration */
The write to RP2_GLOBAL_CMD followed by an immediate read of RP2_GLOBAL_CMD in rp2_reset_asic() is intented to flush out the write, however by then the device is already in reset and cannot respond to a memory cycle access. On platforms such as the Raspberry Pi 4 and others using the pcie-brcmstb.c driver, any memory access to a device that cannot respond is met with a fatal system error, rather than being substituted with all 1s as is usually the case on PC platforms. Swapping the delay and the read ensures that the device has finished resetting before we attempt to read from it. Fixes: 7d9f49afa451 ("serial: rp2: New driver for Comtrol RocketPort 2 cards") Suggested-by: Jim Quinlan <james.quinlan@broadcom.com> Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com> --- drivers/tty/serial/rp2.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)