linux-kernel - Re: Regression: memory corruption on Atmel SAMA5D31

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Date:   Mon, 27 Jun 2022 16:53:45 +0000
From:   <Tudor.Ambarus@...rochip.com>
To:     <peda@...ntia.se>, <regressions@...mhuis.info>,
        <Nicolas.Ferre@...rochip.com>, <alexandre.belloni@...tlin.com>
CC:     <du@...ntia.se>, <Patrice.Vilchez@...rochip.com>,
        <Cristian.Birsan@...rochip.com>, <Ludovic.Desroches@...rochip.com>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <gregkh@...uxfoundation.org>, <saravanak@...gle.com>
Subject: Re: Regression: memory corruption on Atmel SAMA5D31

On 6/27/22 15:26, Tudor.Ambarus@...rochip.com wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> On 6/21/22 13:46, Peter Rosin wrote:
>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>
>> 2022-06-20 at 16:22, Tudor.Ambarus@...rochip.com wrote:
>>>
>>>>
>>>> git@...hub.com:ambarus/linux-0day.git, branch dma-regression-hdmac-v5.18-rc7-4th-attempt
>>>>
>>>
>>> Hi, Peter,
>>>
>>> I've just forced pushed on this branch, I had a typo somewhere and with that fixed I could
>>> no longer reproduce the bug. Tested for ~20 minutes. Would you please test last 3 patches
>>> and tell me if you can still reproduce the bug?
>>
>> Hi!
>>
>> I rebased your patches onto my current branch which is v5.18.2 plus a few unrelated
>> changes (at least they are unrelated after removing the previous workaround to disable
>> nand-dma entirely).
>>
>> The unrelated patches are two backports so that drivers recognize new compatibles [1][2],
>> which should be completely harmless, plus a couple of proposed fixes that happens to fix
>> eeprom issues with the at91 I2C driver from Codrin Ciubotariu [3].
>>
>> On that kernel, I can still reproduce. It seems a bit harder to reproduce the problem now
>> though. If the system is otherwise idle, the sha256sum test did not reproduce in a run of
>> 150+ attempts, but if I let the "real" application run while I do the test, I get a failure rate
>> of about 10%, see below. The real application burns some CPU (but not all of it) and
>> communicates with HW using I2C, native UARTs and two of the four USB-serial ports
>> (FTDI, with the latency set to 1ms as mentioned earlier), so I guess there is more DMA
>> pressure or something? There is a 100mbps network connection, but it was left "idle"
>> during this test.
>>
> 
> Thanks, Peter.
> I got back to the office, I'm rechecking what could go wrong.
> 

Hi, Peter,

Would you please help me with another round of testing? I have difficulties
in reproducing the bug and maybe you can speed up the process while I copy
your testing setup. I made two more patches on top of the same branch [1]. 
My assumption is that the last problem that you saw is that a transfer
could be started multiple times. I think these are the last less invasive
changes that I try, I'll have to rewrite the logic anyway.

Thanks!

[1] To github.com:ambarus/linux-0day.git
   cbb2ddca4618..79c7784dbcf2  dma-regression-hdmac-v5.18-rc7-4th-attempt -> dma-regression-hdmac-v5.18-rc7-4th-attempt