* Re: [PATCH] serial: 8250: 8250_omap: Fix possible interrupt storm
@ 2021-05-28 6:11 ` Vignesh Raghavendra
0 siblings, 0 replies; 23+ messages in thread
From: Vignesh Raghavendra @ 2021-05-28 6:11 UTC (permalink / raw)
To: Tony Lindgren, Greg Kroah-Hartman
Cc: Jiri Slaby, Jan Kiszka, linux-serial, linux-omap,
Linux ARM Mailing List, linux-kernel
Hi,
On 5/28/21 11:09 AM, Tony Lindgren wrote:
> Hi Greg, Vignesh & Jan,
>
> * Greg Kroah-Hartman <gregkh@linuxfoundation.org> [210513 14:17]:
>> On Tue, May 11, 2021 at 08:49:55PM +0530, Vignesh Raghavendra wrote:
>>> It is possible that RX TIMEOUT is signalled after RX FIFO has been
>>> drained, in which case a dummy read of RX FIFO is required to clear RX
>>> TIMEOUT condition. Otherwise, RX TIMEOUT condition is not cleared
>>> leading to an interrupt storm
>>>
>>> Cc: stable@vger.kernel.org
>>
>> How far back does this need to go? What commit id does this fix? What
>> caused this to just show up now vs. previously?
Sorry, I missed this reply. Issue was reported on AM65x SoC with custom
test case from Jan Kiszka that stressed UART with rapid baudrate changes
from 9600 to 4M along with data transfer.
Based on the condition that led to interrupt storm, I inferred it to
affect all SoCs with 8250 OMAP UARTs. But that seems thats not the best
idea as seen from OMAP3 regression.
Greg,
Could you please drop the patch? Very sorry for the inconvenience..
>
> I just noticed this causes the following regression in Linux next when
> pressing a key on uart console after boot at least on omap3. This seems
> to happen on serial_port_in(port, UART_RX) in the quirk handling.
>
> Vignesh, it seems this quirk needs some soc specific flag added to
> it maybe? Or maybe UART_OMAP_RX_LVL register is not available for
> all the SoCs?
>
Yes indeed :(
> I think it's best to drop this patch until the issues are resolved,
> also there are some open comments above that might be answered by
> limiting this quirk to a specific range of SoCs :)
>
Oops, I did test patch AM33xx assuming its equivalent to OMAP3, but UART
IP is quite different. I will respin the patch making sure, workaround
applies only to AM65x and K3 SoCs.
Regards
Vignesh
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [PATCH] serial: 8250: 8250_omap: Fix possible interrupt storm
2021-05-28 6:11 ` Vignesh Raghavendra
@ 2021-05-28 9:00 ` Greg Kroah-Hartman
-1 siblings, 0 replies; 23+ messages in thread
From: Greg Kroah-Hartman @ 2021-05-28 9:00 UTC (permalink / raw)
To: Vignesh Raghavendra
Cc: Tony Lindgren, Jiri Slaby, Jan Kiszka, linux-serial, linux-omap,
Linux ARM Mailing List, linux-kernel
On Fri, May 28, 2021 at 11:41:36AM +0530, Vignesh Raghavendra wrote:
> Hi,
>
> On 5/28/21 11:09 AM, Tony Lindgren wrote:
> > Hi Greg, Vignesh & Jan,
> >
> > * Greg Kroah-Hartman <gregkh@linuxfoundation.org> [210513 14:17]:
> >> On Tue, May 11, 2021 at 08:49:55PM +0530, Vignesh Raghavendra wrote:
> >>> It is possible that RX TIMEOUT is signalled after RX FIFO has been
> >>> drained, in which case a dummy read of RX FIFO is required to clear RX
> >>> TIMEOUT condition. Otherwise, RX TIMEOUT condition is not cleared
> >>> leading to an interrupt storm
> >>>
> >>> Cc: stable@vger.kernel.org
> >>
> >> How far back does this need to go? What commit id does this fix? What
> >> caused this to just show up now vs. previously?
>
> Sorry, I missed this reply. Issue was reported on AM65x SoC with custom
> test case from Jan Kiszka that stressed UART with rapid baudrate changes
> from 9600 to 4M along with data transfer.
>
> Based on the condition that led to interrupt storm, I inferred it to
> affect all SoCs with 8250 OMAP UARTs. But that seems thats not the best
> idea as seen from OMAP3 regression.
>
> Greg,
>
> Could you please drop the patch? Very sorry for the inconvenience..
Now reverted, thanks.
greg k-h
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [PATCH] serial: 8250: 8250_omap: Fix possible interrupt storm
@ 2021-05-28 9:00 ` Greg Kroah-Hartman
0 siblings, 0 replies; 23+ messages in thread
From: Greg Kroah-Hartman @ 2021-05-28 9:00 UTC (permalink / raw)
To: Vignesh Raghavendra
Cc: Tony Lindgren, Jiri Slaby, Jan Kiszka, linux-serial, linux-omap,
Linux ARM Mailing List, linux-kernel
On Fri, May 28, 2021 at 11:41:36AM +0530, Vignesh Raghavendra wrote:
> Hi,
>
> On 5/28/21 11:09 AM, Tony Lindgren wrote:
> > Hi Greg, Vignesh & Jan,
> >
> > * Greg Kroah-Hartman <gregkh@linuxfoundation.org> [210513 14:17]:
> >> On Tue, May 11, 2021 at 08:49:55PM +0530, Vignesh Raghavendra wrote:
> >>> It is possible that RX TIMEOUT is signalled after RX FIFO has been
> >>> drained, in which case a dummy read of RX FIFO is required to clear RX
> >>> TIMEOUT condition. Otherwise, RX TIMEOUT condition is not cleared
> >>> leading to an interrupt storm
> >>>
> >>> Cc: stable@vger.kernel.org
> >>
> >> How far back does this need to go? What commit id does this fix? What
> >> caused this to just show up now vs. previously?
>
> Sorry, I missed this reply. Issue was reported on AM65x SoC with custom
> test case from Jan Kiszka that stressed UART with rapid baudrate changes
> from 9600 to 4M along with data transfer.
>
> Based on the condition that led to interrupt storm, I inferred it to
> affect all SoCs with 8250 OMAP UARTs. But that seems thats not the best
> idea as seen from OMAP3 regression.
>
> Greg,
>
> Could you please drop the patch? Very sorry for the inconvenience..
Now reverted, thanks.
greg k-h
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [PATCH] serial: 8250: 8250_omap: Fix possible interrupt storm
2021-05-28 6:11 ` Vignesh Raghavendra
@ 2021-06-22 6:15 ` Jan Kiszka
-1 siblings, 0 replies; 23+ messages in thread
From: Jan Kiszka @ 2021-06-22 6:15 UTC (permalink / raw)
To: Vignesh Raghavendra, Tony Lindgren, Greg Kroah-Hartman
Cc: Jiri Slaby, linux-serial, linux-omap, Linux ARM Mailing List,
linux-kernel
On 28.05.21 08:11, Vignesh Raghavendra wrote:
> Hi,
>
> On 5/28/21 11:09 AM, Tony Lindgren wrote:
>> Hi Greg, Vignesh & Jan,
>>
>> * Greg Kroah-Hartman <gregkh@linuxfoundation.org> [210513 14:17]:
>>> On Tue, May 11, 2021 at 08:49:55PM +0530, Vignesh Raghavendra wrote:
>>>> It is possible that RX TIMEOUT is signalled after RX FIFO has been
>>>> drained, in which case a dummy read of RX FIFO is required to clear RX
>>>> TIMEOUT condition. Otherwise, RX TIMEOUT condition is not cleared
>>>> leading to an interrupt storm
>>>>
>>>> Cc: stable@vger.kernel.org
>>>
>>> How far back does this need to go? What commit id does this fix? What
>>> caused this to just show up now vs. previously?
>
> Sorry, I missed this reply. Issue was reported on AM65x SoC with custom
> test case from Jan Kiszka that stressed UART with rapid baudrate changes
> from 9600 to 4M along with data transfer.
>
> Based on the condition that led to interrupt storm, I inferred it to
> affect all SoCs with 8250 OMAP UARTs. But that seems thats not the best
> idea as seen from OMAP3 regression.
>
> Greg,
>
> Could you please drop the patch? Very sorry for the inconvenience..
>
>>
>> I just noticed this causes the following regression in Linux next when
>> pressing a key on uart console after boot at least on omap3. This seems
>> to happen on serial_port_in(port, UART_RX) in the quirk handling.
>>
>> Vignesh, it seems this quirk needs some soc specific flag added to
>> it maybe? Or maybe UART_OMAP_RX_LVL register is not available for
>> all the SoCs?
>>
>
> Yes indeed :(
>
>> I think it's best to drop this patch until the issues are resolved,
>> also there are some open comments above that might be answered by
>> limiting this quirk to a specific range of SoCs :)
>>
>
> Oops, I did test patch AM33xx assuming its equivalent to OMAP3, but UART
> IP is quite different. I will respin the patch making sure, workaround
> applies only to AM65x and K3 SoCs.
>
> Regards
> Vignesh
>
What's the status here for AM65x? The issue remains present on that
platform, and I was hoping to see a quick follow up that limit the fix
to that target.
Jan
--
Siemens AG, T RDA IOT
Corporate Competence Center Embedded Linux
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [PATCH] serial: 8250: 8250_omap: Fix possible interrupt storm
@ 2021-06-22 6:15 ` Jan Kiszka
0 siblings, 0 replies; 23+ messages in thread
From: Jan Kiszka @ 2021-06-22 6:15 UTC (permalink / raw)
To: Vignesh Raghavendra, Tony Lindgren, Greg Kroah-Hartman
Cc: Jiri Slaby, linux-serial, linux-omap, Linux ARM Mailing List,
linux-kernel
On 28.05.21 08:11, Vignesh Raghavendra wrote:
> Hi,
>
> On 5/28/21 11:09 AM, Tony Lindgren wrote:
>> Hi Greg, Vignesh & Jan,
>>
>> * Greg Kroah-Hartman <gregkh@linuxfoundation.org> [210513 14:17]:
>>> On Tue, May 11, 2021 at 08:49:55PM +0530, Vignesh Raghavendra wrote:
>>>> It is possible that RX TIMEOUT is signalled after RX FIFO has been
>>>> drained, in which case a dummy read of RX FIFO is required to clear RX
>>>> TIMEOUT condition. Otherwise, RX TIMEOUT condition is not cleared
>>>> leading to an interrupt storm
>>>>
>>>> Cc: stable@vger.kernel.org
>>>
>>> How far back does this need to go? What commit id does this fix? What
>>> caused this to just show up now vs. previously?
>
> Sorry, I missed this reply. Issue was reported on AM65x SoC with custom
> test case from Jan Kiszka that stressed UART with rapid baudrate changes
> from 9600 to 4M along with data transfer.
>
> Based on the condition that led to interrupt storm, I inferred it to
> affect all SoCs with 8250 OMAP UARTs. But that seems thats not the best
> idea as seen from OMAP3 regression.
>
> Greg,
>
> Could you please drop the patch? Very sorry for the inconvenience..
>
>>
>> I just noticed this causes the following regression in Linux next when
>> pressing a key on uart console after boot at least on omap3. This seems
>> to happen on serial_port_in(port, UART_RX) in the quirk handling.
>>
>> Vignesh, it seems this quirk needs some soc specific flag added to
>> it maybe? Or maybe UART_OMAP_RX_LVL register is not available for
>> all the SoCs?
>>
>
> Yes indeed :(
>
>> I think it's best to drop this patch until the issues are resolved,
>> also there are some open comments above that might be answered by
>> limiting this quirk to a specific range of SoCs :)
>>
>
> Oops, I did test patch AM33xx assuming its equivalent to OMAP3, but UART
> IP is quite different. I will respin the patch making sure, workaround
> applies only to AM65x and K3 SoCs.
>
> Regards
> Vignesh
>
What's the status here for AM65x? The issue remains present on that
platform, and I was hoping to see a quick follow up that limit the fix
to that target.
Jan
--
Siemens AG, T RDA IOT
Corporate Competence Center Embedded Linux
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [PATCH] serial: 8250: 8250_omap: Fix possible interrupt storm
2021-06-22 6:15 ` Jan Kiszka
@ 2021-06-22 6:23 ` Vignesh Raghavendra
-1 siblings, 0 replies; 23+ messages in thread
From: Vignesh Raghavendra @ 2021-06-22 6:23 UTC (permalink / raw)
To: Jan Kiszka, Tony Lindgren, Greg Kroah-Hartman
Cc: Jiri Slaby, linux-serial, linux-omap, Linux ARM Mailing List,
linux-kernel
On 6/22/21 11:45 AM, Jan Kiszka wrote:
>>> Vignesh, it seems this quirk needs some soc specific flag added to
>>> it maybe? Or maybe UART_OMAP_RX_LVL register is not available for
>>> all the SoCs?
>>>
>> Yes indeed :(
>>
>>> I think it's best to drop this patch until the issues are resolved,
>>> also there are some open comments above that might be answered by
>>> limiting this quirk to a specific range of SoCs :)
>>>
>> Oops, I did test patch AM33xx assuming its equivalent to OMAP3, but UART
>> IP is quite different. I will respin the patch making sure, workaround
>> applies only to AM65x and K3 SoCs.
>>
>> Regards
>> Vignesh
>>
> What's the status here for AM65x? The issue remains present on that
> platform, and I was hoping to see a quick follow up that limit the fix
> to that target.
>
Sorry for the delay, I am trying to find which other TI SoCs are
affected by this issue. But that exercise will need a bit more time.
Will send a fix to address K3 SoCs like AM65x today/tomo.
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [PATCH] serial: 8250: 8250_omap: Fix possible interrupt storm
@ 2021-06-22 6:23 ` Vignesh Raghavendra
0 siblings, 0 replies; 23+ messages in thread
From: Vignesh Raghavendra @ 2021-06-22 6:23 UTC (permalink / raw)
To: Jan Kiszka, Tony Lindgren, Greg Kroah-Hartman
Cc: Jiri Slaby, linux-serial, linux-omap, Linux ARM Mailing List,
linux-kernel
On 6/22/21 11:45 AM, Jan Kiszka wrote:
>>> Vignesh, it seems this quirk needs some soc specific flag added to
>>> it maybe? Or maybe UART_OMAP_RX_LVL register is not available for
>>> all the SoCs?
>>>
>> Yes indeed :(
>>
>>> I think it's best to drop this patch until the issues are resolved,
>>> also there are some open comments above that might be answered by
>>> limiting this quirk to a specific range of SoCs :)
>>>
>> Oops, I did test patch AM33xx assuming its equivalent to OMAP3, but UART
>> IP is quite different. I will respin the patch making sure, workaround
>> applies only to AM65x and K3 SoCs.
>>
>> Regards
>> Vignesh
>>
> What's the status here for AM65x? The issue remains present on that
> platform, and I was hoping to see a quick follow up that limit the fix
> to that target.
>
Sorry for the delay, I am trying to find which other TI SoCs are
affected by this issue. But that exercise will need a bit more time.
Will send a fix to address K3 SoCs like AM65x today/tomo.
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [PATCH] serial: 8250: 8250_omap: Fix possible interrupt storm
2021-06-22 6:23 ` Vignesh Raghavendra
(?)
@ 2021-07-12 20:27 ` andy
2021-07-13 8:54 ` Vignesh Raghavendra
-1 siblings, 1 reply; 23+ messages in thread
From: andy @ 2021-07-12 20:27 UTC (permalink / raw)
To: Vignesh Raghavendra
Cc: Jan Kiszka, Tony Lindgren, Greg Kroah-Hartman, Jiri Slaby,
linux-serial, linux-omap, Linux ARM Mailing List, linux-kernel
Tue, Jun 22, 2021 at 11:53:38AM +0530, Vignesh Raghavendra kirjoitti:
> On 6/22/21 11:45 AM, Jan Kiszka wrote:
> >>> Vignesh, it seems this quirk needs some soc specific flag added to
> >>> it maybe? Or maybe UART_OMAP_RX_LVL register is not available for
> >>> all the SoCs?
> >>>
> >> Yes indeed :(
> >>
> >>> I think it's best to drop this patch until the issues are resolved,
> >>> also there are some open comments above that might be answered by
> >>> limiting this quirk to a specific range of SoCs :)
> >>>
> >> Oops, I did test patch AM33xx assuming its equivalent to OMAP3, but UART
> >> IP is quite different. I will respin the patch making sure, workaround
> >> applies only to AM65x and K3 SoCs.
> >>
> >> Regards
> >> Vignesh
> >>
> > What's the status here for AM65x? The issue remains present on that
> > platform, and I was hoping to see a quick follow up that limit the fix
> > to that target.
>
> Sorry for the delay, I am trying to find which other TI SoCs are
> affected by this issue. But that exercise will need a bit more time.
> Will send a fix to address K3 SoCs like AM65x today/tomo.
This all reminds me the very similar issue one found on Intel integrated
(Synopsys DesignWare based) UARTs:
https://lore.kernel.org/linux-serial/20170206233000.3021-1-dianders@chromium.org/
https://lore.kernel.org/linux-serial/1440015124-28393-1-git-send-email-california.l.sullivan@intel.com/
--
With Best Regards,
Andy Shevchenko
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [PATCH] serial: 8250: 8250_omap: Fix possible interrupt storm
2021-07-12 20:27 ` andy
@ 2021-07-13 8:54 ` Vignesh Raghavendra
0 siblings, 0 replies; 23+ messages in thread
From: Vignesh Raghavendra @ 2021-07-13 8:54 UTC (permalink / raw)
To: linux-serial
Cc: Jan Kiszka, Tony Lindgren, Greg Kroah-Hartman, Jiri Slaby,
linux-omap, Linux ARM Mailing List, linux-kernel
On 7/13/21 1:57 AM, andy@surfacebook.localdomain wrote:
> Tue, Jun 22, 2021 at 11:53:38AM +0530, Vignesh Raghavendra kirjoitti:
>> On 6/22/21 11:45 AM, Jan Kiszka wrote:
>>>>> Vignesh, it seems this quirk needs some soc specific flag added to
>>>>> it maybe? Or maybe UART_OMAP_RX_LVL register is not available for
>>>>> all the SoCs?
>>>>>
>>>> Yes indeed :(
>>>>
>>>>> I think it's best to drop this patch until the issues are resolved,
>>>>> also there are some open comments above that might be answered by
>>>>> limiting this quirk to a specific range of SoCs :)
>>>>>
>>>> Oops, I did test patch AM33xx assuming its equivalent to OMAP3, but UART
>>>> IP is quite different. I will respin the patch making sure, workaround
>>>> applies only to AM65x and K3 SoCs.
>>>>
>>>> Regards
>>>> Vignesh
>>>>
>>> What's the status here for AM65x? The issue remains present on that
>>> platform, and I was hoping to see a quick follow up that limit the fix
>>> to that target.
>>
>> Sorry for the delay, I am trying to find which other TI SoCs are
>> affected by this issue. But that exercise will need a bit more time.
>> Will send a fix to address K3 SoCs like AM65x today/tomo.
>
> This all reminds me the very similar issue one found on Intel integrated
> (Synopsys DesignWare based) UARTs:
>
Hmm, yes, seems like common problem with some 8250 UARTs although not
all TI SoCs show this behavior even though they all claim 8250 compatible.
> https://lore.kernel.org/linux-serial/20170206233000.3021-1-dianders@chromium.org/
I am not sure if reading UART_LSR is a good idea in the above patch.
Some flags in LSR register are cleared on read (at least that's the case
for UARTs on TI SoCs) and thus can result in loss of error/FIFO status
information.
> https://lore.kernel.org/linux-serial/1440015124-28393-1-git-send-email-california.l.sullivan@intel.com/
>
Looks like this never made it.
Given the quirks associated with 8250 UARTs, workarounds would need to
be tied to specific variants, so I don't know if its possible to
implement the fix in 8250 core IRQ handler.
PS: v2 of $patch is already merged.
Regards
Vignesh
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [PATCH] serial: 8250: 8250_omap: Fix possible interrupt storm
@ 2021-07-13 8:54 ` Vignesh Raghavendra
0 siblings, 0 replies; 23+ messages in thread
From: Vignesh Raghavendra @ 2021-07-13 8:54 UTC (permalink / raw)
To: linux-serial
Cc: Jan Kiszka, Tony Lindgren, Greg Kroah-Hartman, Jiri Slaby,
linux-omap, Linux ARM Mailing List, linux-kernel
On 7/13/21 1:57 AM, andy@surfacebook.localdomain wrote:
> Tue, Jun 22, 2021 at 11:53:38AM +0530, Vignesh Raghavendra kirjoitti:
>> On 6/22/21 11:45 AM, Jan Kiszka wrote:
>>>>> Vignesh, it seems this quirk needs some soc specific flag added to
>>>>> it maybe? Or maybe UART_OMAP_RX_LVL register is not available for
>>>>> all the SoCs?
>>>>>
>>>> Yes indeed :(
>>>>
>>>>> I think it's best to drop this patch until the issues are resolved,
>>>>> also there are some open comments above that might be answered by
>>>>> limiting this quirk to a specific range of SoCs :)
>>>>>
>>>> Oops, I did test patch AM33xx assuming its equivalent to OMAP3, but UART
>>>> IP is quite different. I will respin the patch making sure, workaround
>>>> applies only to AM65x and K3 SoCs.
>>>>
>>>> Regards
>>>> Vignesh
>>>>
>>> What's the status here for AM65x? The issue remains present on that
>>> platform, and I was hoping to see a quick follow up that limit the fix
>>> to that target.
>>
>> Sorry for the delay, I am trying to find which other TI SoCs are
>> affected by this issue. But that exercise will need a bit more time.
>> Will send a fix to address K3 SoCs like AM65x today/tomo.
>
> This all reminds me the very similar issue one found on Intel integrated
> (Synopsys DesignWare based) UARTs:
>
Hmm, yes, seems like common problem with some 8250 UARTs although not
all TI SoCs show this behavior even though they all claim 8250 compatible.
> https://lore.kernel.org/linux-serial/20170206233000.3021-1-dianders@chromium.org/
I am not sure if reading UART_LSR is a good idea in the above patch.
Some flags in LSR register are cleared on read (at least that's the case
for UARTs on TI SoCs) and thus can result in loss of error/FIFO status
information.
> https://lore.kernel.org/linux-serial/1440015124-28393-1-git-send-email-california.l.sullivan@intel.com/
>
Looks like this never made it.
Given the quirks associated with 8250 UARTs, workarounds would need to
be tied to specific variants, so I don't know if its possible to
implement the fix in 8250 core IRQ handler.
PS: v2 of $patch is already merged.
Regards
Vignesh
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [PATCH] serial: 8250: 8250_omap: Fix possible interrupt storm
2021-07-13 8:54 ` Vignesh Raghavendra
@ 2021-07-13 9:09 ` Andy Shevchenko
-1 siblings, 0 replies; 23+ messages in thread
From: Andy Shevchenko @ 2021-07-13 9:09 UTC (permalink / raw)
To: Vignesh Raghavendra
Cc: open list:SERIAL DRIVERS, Jan Kiszka, Tony Lindgren,
Greg Kroah-Hartman, Jiri Slaby, Linux OMAP Mailing List,
Linux ARM Mailing List, Linux Kernel Mailing List
On Tue, Jul 13, 2021 at 11:54 AM Vignesh Raghavendra <vigneshr@ti.com> wrote:
> On 7/13/21 1:57 AM, andy@surfacebook.localdomain wrote:
> > Tue, Jun 22, 2021 at 11:53:38AM +0530, Vignesh Raghavendra kirjoitti:
> >> On 6/22/21 11:45 AM, Jan Kiszka wrote:
> >>>>> Vignesh, it seems this quirk needs some soc specific flag added to
> >>>>> it maybe? Or maybe UART_OMAP_RX_LVL register is not available for
> >>>>> all the SoCs?
> >>>>>
> >>>> Yes indeed :(
> >>>>
> >>>>> I think it's best to drop this patch until the issues are resolved,
> >>>>> also there are some open comments above that might be answered by
> >>>>> limiting this quirk to a specific range of SoCs :)
> >>>>>
> >>>> Oops, I did test patch AM33xx assuming its equivalent to OMAP3, but UART
> >>>> IP is quite different. I will respin the patch making sure, workaround
> >>>> applies only to AM65x and K3 SoCs.
> >>>>
> >>>> Regards
> >>>> Vignesh
> >>>>
> >>> What's the status here for AM65x? The issue remains present on that
> >>> platform, and I was hoping to see a quick follow up that limit the fix
> >>> to that target.
> >>
> >> Sorry for the delay, I am trying to find which other TI SoCs are
> >> affected by this issue. But that exercise will need a bit more time.
> >> Will send a fix to address K3 SoCs like AM65x today/tomo.
> >
> > This all reminds me the very similar issue one found on Intel integrated
> > (Synopsys DesignWare based) UARTs:
> >
>
> Hmm, yes, seems like common problem with some 8250 UARTs although not
> all TI SoCs show this behavior even though they all claim 8250 compatible.
>
> > https://lore.kernel.org/linux-serial/20170206233000.3021-1-dianders@chromium.org/
>
> I am not sure if reading UART_LSR is a good idea in the above patch.
> Some flags in LSR register are cleared on read (at least that's the case
> for UARTs on TI SoCs) and thus can result in loss of error/FIFO status
> information.
>
> > https://lore.kernel.org/linux-serial/1440015124-28393-1-git-send-email-california.l.sullivan@intel.com/
> >
>
> Looks like this never made it.
>
> Given the quirks associated with 8250 UARTs, workarounds would need to
> be tied to specific variants, so I don't know if its possible to
> implement the fix in 8250 core IRQ handler.
I believe they are all are derivatives from Synopsys DesignWare one or
another version of it.
> PS: v2 of $patch is already merged.
I noticed after sending that email.
--
With Best Regards,
Andy Shevchenko
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [PATCH] serial: 8250: 8250_omap: Fix possible interrupt storm
@ 2021-07-13 9:09 ` Andy Shevchenko
0 siblings, 0 replies; 23+ messages in thread
From: Andy Shevchenko @ 2021-07-13 9:09 UTC (permalink / raw)
To: Vignesh Raghavendra
Cc: open list:SERIAL DRIVERS, Jan Kiszka, Tony Lindgren,
Greg Kroah-Hartman, Jiri Slaby, Linux OMAP Mailing List,
Linux ARM Mailing List, Linux Kernel Mailing List
On Tue, Jul 13, 2021 at 11:54 AM Vignesh Raghavendra <vigneshr@ti.com> wrote:
> On 7/13/21 1:57 AM, andy@surfacebook.localdomain wrote:
> > Tue, Jun 22, 2021 at 11:53:38AM +0530, Vignesh Raghavendra kirjoitti:
> >> On 6/22/21 11:45 AM, Jan Kiszka wrote:
> >>>>> Vignesh, it seems this quirk needs some soc specific flag added to
> >>>>> it maybe? Or maybe UART_OMAP_RX_LVL register is not available for
> >>>>> all the SoCs?
> >>>>>
> >>>> Yes indeed :(
> >>>>
> >>>>> I think it's best to drop this patch until the issues are resolved,
> >>>>> also there are some open comments above that might be answered by
> >>>>> limiting this quirk to a specific range of SoCs :)
> >>>>>
> >>>> Oops, I did test patch AM33xx assuming its equivalent to OMAP3, but UART
> >>>> IP is quite different. I will respin the patch making sure, workaround
> >>>> applies only to AM65x and K3 SoCs.
> >>>>
> >>>> Regards
> >>>> Vignesh
> >>>>
> >>> What's the status here for AM65x? The issue remains present on that
> >>> platform, and I was hoping to see a quick follow up that limit the fix
> >>> to that target.
> >>
> >> Sorry for the delay, I am trying to find which other TI SoCs are
> >> affected by this issue. But that exercise will need a bit more time.
> >> Will send a fix to address K3 SoCs like AM65x today/tomo.
> >
> > This all reminds me the very similar issue one found on Intel integrated
> > (Synopsys DesignWare based) UARTs:
> >
>
> Hmm, yes, seems like common problem with some 8250 UARTs although not
> all TI SoCs show this behavior even though they all claim 8250 compatible.
>
> > https://lore.kernel.org/linux-serial/20170206233000.3021-1-dianders@chromium.org/
>
> I am not sure if reading UART_LSR is a good idea in the above patch.
> Some flags in LSR register are cleared on read (at least that's the case
> for UARTs on TI SoCs) and thus can result in loss of error/FIFO status
> information.
>
> > https://lore.kernel.org/linux-serial/1440015124-28393-1-git-send-email-california.l.sullivan@intel.com/
> >
>
> Looks like this never made it.
>
> Given the quirks associated with 8250 UARTs, workarounds would need to
> be tied to specific variants, so I don't know if its possible to
> implement the fix in 8250 core IRQ handler.
I believe they are all are derivatives from Synopsys DesignWare one or
another version of it.
> PS: v2 of $patch is already merged.
I noticed after sending that email.
--
With Best Regards,
Andy Shevchenko
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [PATCH] serial: 8250: 8250_omap: Fix possible interrupt storm
2021-07-13 8:54 ` Vignesh Raghavendra
@ 2021-07-13 9:13 ` Andy Shevchenko
-1 siblings, 0 replies; 23+ messages in thread
From: Andy Shevchenko @ 2021-07-13 9:13 UTC (permalink / raw)
To: Vignesh Raghavendra
Cc: open list:SERIAL DRIVERS, Jan Kiszka, Tony Lindgren,
Greg Kroah-Hartman, Jiri Slaby, Linux OMAP Mailing List,
Linux ARM Mailing List, Linux Kernel Mailing List
On Tue, Jul 13, 2021 at 11:54 AM Vignesh Raghavendra <vigneshr@ti.com> wrote:
> On 7/13/21 1:57 AM, andy@surfacebook.localdomain wrote:
> > Tue, Jun 22, 2021 at 11:53:38AM +0530, Vignesh Raghavendra kirjoitti:
...
> > https://lore.kernel.org/linux-serial/20170206233000.3021-1-dianders@chromium.org/
>
> I am not sure if reading UART_LSR is a good idea in the above patch.
> Some flags in LSR register are cleared on read (at least that's the case
> for UARTs on TI SoCs) and thus can result in loss of error/FIFO status
> information.
>
> > https://lore.kernel.org/linux-serial/1440015124-28393-1-git-send-email-california.l.sullivan@intel.com/
>
> Looks like this never made it.
Forgot to react to the above. Yes, they never made it because I
believe due to the exact reason you mentioned above. Also California
set up different experiments IIRC and it shows that the problem didn;t
fully disappear with his approach. But maybe yours will work better
(at least it's not the first time I have seen it on different hardware
according to people's contributions).
--
With Best Regards,
Andy Shevchenko
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [PATCH] serial: 8250: 8250_omap: Fix possible interrupt storm
@ 2021-07-13 9:13 ` Andy Shevchenko
0 siblings, 0 replies; 23+ messages in thread
From: Andy Shevchenko @ 2021-07-13 9:13 UTC (permalink / raw)
To: Vignesh Raghavendra
Cc: open list:SERIAL DRIVERS, Jan Kiszka, Tony Lindgren,
Greg Kroah-Hartman, Jiri Slaby, Linux OMAP Mailing List,
Linux ARM Mailing List, Linux Kernel Mailing List
On Tue, Jul 13, 2021 at 11:54 AM Vignesh Raghavendra <vigneshr@ti.com> wrote:
> On 7/13/21 1:57 AM, andy@surfacebook.localdomain wrote:
> > Tue, Jun 22, 2021 at 11:53:38AM +0530, Vignesh Raghavendra kirjoitti:
...
> > https://lore.kernel.org/linux-serial/20170206233000.3021-1-dianders@chromium.org/
>
> I am not sure if reading UART_LSR is a good idea in the above patch.
> Some flags in LSR register are cleared on read (at least that's the case
> for UARTs on TI SoCs) and thus can result in loss of error/FIFO status
> information.
>
> > https://lore.kernel.org/linux-serial/1440015124-28393-1-git-send-email-california.l.sullivan@intel.com/
>
> Looks like this never made it.
Forgot to react to the above. Yes, they never made it because I
believe due to the exact reason you mentioned above. Also California
set up different experiments IIRC and it shows that the problem didn;t
fully disappear with his approach. But maybe yours will work better
(at least it's not the first time I have seen it on different hardware
according to people's contributions).
--
With Best Regards,
Andy Shevchenko
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [PATCH] serial: 8250: 8250_omap: Fix possible interrupt storm
2021-07-13 9:13 ` Andy Shevchenko
@ 2021-07-27 10:39 ` Tony Lindgren
-1 siblings, 0 replies; 23+ messages in thread
From: Tony Lindgren @ 2021-07-27 10:39 UTC (permalink / raw)
To: Andy Shevchenko
Cc: Vignesh Raghavendra, open list:SERIAL DRIVERS, Jan Kiszka,
Greg Kroah-Hartman, Jiri Slaby, Linux OMAP Mailing List,
Linux ARM Mailing List, Linux Kernel Mailing List
* Andy Shevchenko <andy.shevchenko@gmail.com> [210713 09:14]:
> On Tue, Jul 13, 2021 at 11:54 AM Vignesh Raghavendra <vigneshr@ti.com> wrote:
> > On 7/13/21 1:57 AM, andy@surfacebook.localdomain wrote:
> > > Tue, Jun 22, 2021 at 11:53:38AM +0530, Vignesh Raghavendra kirjoitti:
>
> ...
>
> > > https://lore.kernel.org/linux-serial/20170206233000.3021-1-dianders@chromium.org/
> >
> > I am not sure if reading UART_LSR is a good idea in the above patch.
> > Some flags in LSR register are cleared on read (at least that's the case
> > for UARTs on TI SoCs) and thus can result in loss of error/FIFO status
> > information.
> >
> > > https://lore.kernel.org/linux-serial/1440015124-28393-1-git-send-email-california.l.sullivan@intel.com/
> >
> > Looks like this never made it.
>
> Forgot to react to the above. Yes, they never made it because I
> believe due to the exact reason you mentioned above. Also California
> set up different experiments IIRC and it shows that the problem didn;t
> fully disappear with his approach. But maybe yours will work better
> (at least it's not the first time I have seen it on different hardware
> according to people's contributions).
Not sure if this is the same issue with noisy lines, but see also the
following in case it's related:
[PATCH 2/2] serial: 8250_omap: Handle optional overrun-throttle-ms property
Also available at [0] below.
Regards,
Tony
[0] https://lore.kernel.org/linux-omap/20210727103533.51547-1-tony@atomide.com/T/#m5f9da26c32503f2937d3d5977310ca337fa0cb5a
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [PATCH] serial: 8250: 8250_omap: Fix possible interrupt storm
@ 2021-07-27 10:39 ` Tony Lindgren
0 siblings, 0 replies; 23+ messages in thread
From: Tony Lindgren @ 2021-07-27 10:39 UTC (permalink / raw)
To: Andy Shevchenko
Cc: Vignesh Raghavendra, open list:SERIAL DRIVERS, Jan Kiszka,
Greg Kroah-Hartman, Jiri Slaby, Linux OMAP Mailing List,
Linux ARM Mailing List, Linux Kernel Mailing List
* Andy Shevchenko <andy.shevchenko@gmail.com> [210713 09:14]:
> On Tue, Jul 13, 2021 at 11:54 AM Vignesh Raghavendra <vigneshr@ti.com> wrote:
> > On 7/13/21 1:57 AM, andy@surfacebook.localdomain wrote:
> > > Tue, Jun 22, 2021 at 11:53:38AM +0530, Vignesh Raghavendra kirjoitti:
>
> ...
>
> > > https://lore.kernel.org/linux-serial/20170206233000.3021-1-dianders@chromium.org/
> >
> > I am not sure if reading UART_LSR is a good idea in the above patch.
> > Some flags in LSR register are cleared on read (at least that's the case
> > for UARTs on TI SoCs) and thus can result in loss of error/FIFO status
> > information.
> >
> > > https://lore.kernel.org/linux-serial/1440015124-28393-1-git-send-email-california.l.sullivan@intel.com/
> >
> > Looks like this never made it.
>
> Forgot to react to the above. Yes, they never made it because I
> believe due to the exact reason you mentioned above. Also California
> set up different experiments IIRC and it shows that the problem didn;t
> fully disappear with his approach. But maybe yours will work better
> (at least it's not the first time I have seen it on different hardware
> according to people's contributions).
Not sure if this is the same issue with noisy lines, but see also the
following in case it's related:
[PATCH 2/2] serial: 8250_omap: Handle optional overrun-throttle-ms property
Also available at [0] below.
Regards,
Tony
[0] https://lore.kernel.org/linux-omap/20210727103533.51547-1-tony@atomide.com/T/#m5f9da26c32503f2937d3d5977310ca337fa0cb5a
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 23+ messages in thread