drm/fbdev-dma: regression

[Thomas Zimmermann]

Hi


Am 11.11.24 um 12:51 schrieb Thorsten Leemhuis:
> [CCing a few more lists]
>
> On 21.10.24 15:03, Nuno Gonçalves wrote:
>> Since 5ab91447aa13b8b98bc11f5326f33500b0ee2c48 and still happening in
>> master, I often get a kernel crash, either a "Unable to handle kernel
>> NULL pointer dereference at virtual address" or "Unable to handle
>> kernel paging request at virtual address".
>>
>> This happens in ARM64 with ili9225 and display size 220, 176. It also
>> happens in another board with a different tinydrm driver and size 320,
>> 240.
>>
>> I've reported in 2022 a bug (that you fixed, thanks!), where it was
>> related to screen size causing non alignment of scanlines and pages.
>> I've not investigated further this time as I was not doing any driver
>> development, but let me know if I can do any further testing.
> Thx for the report. I might be missing something, but from here it looks
> like nothing happened. So allow me to ask:
>
> What's the status? Did anyone look into this? Is this sill happening?

I briefly looked into this bug report some time ago.

The patch in question changes the whole memory management of the 
affected code. It's also noteworthy that most of it has been reworked 
for the upcoming v6.12. Maybe this already fixed the problem. Kernel 
v6.11-rc7 added commit 5a498d4d06d6 ("drm/fbdev-dma: Only install 
deferred I/O if necessary"), which possibly fixes the problem as well.

But there's no explicit fix for this problem and I have not seen any 
other related reports. Any further information is welcome.

Best regards
Thomas

>
> Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
> --
> Everything you wanna know about Linux kernel regression tracking:
> https://linux-regtracking.leemhuis.info/about/#tldr
> If I did something stupid, please tell me, as explained on that page.
>
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-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
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