On 28.05.21 08:11, Vignesh Raghavendra wrote:

Hi,

On 5/28/21 11:09 AM, Tony Lindgren wrote:

quoted

Hi Greg, Vignesh & Jan,

* Greg Kroah-Hartman [off-list ref] [210513 14:17]:

quoted

On Tue, May 11, 2021 at 08:49:55PM +0530, Vignesh Raghavendra wrote:

quoted

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..

quoted

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 :(

quoted

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

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