NACK/Cmnt: [PATCH 0/1][SRU][M] dell-uart-backlight fails to communicate

[Stefan Bader]

On 14.09.23 12:13, AceLan Kao wrote:
> From: "Chia-Lin Kao (AceLan)" <acelan.kao at canonical.com>
> 
> BugLink: https://bugs.launchpad.net/bug/2035299
> 
> [Impact]
> Boots up the system and sometimes we can see below messages and that leads
> to backlight driver doesn't get loaded.
> 
> [ 86.424880] dell_uart_backlight:dell_uart_get_display_mode:tx: 6a 10 85
> [ 86.603936] [7439] dell_uart_backlight:dell_uart_get_display_mode:rx: NULL
> [ 87.596047] dell_uart_backlight:dell_uart_get_display_mode:tx: 6a 10 85
> [ 87.775209] [7439] dell_uart_backlight:dell_uart_get_display_mode:rx: NULL
> 
> [Fix]
> After applying the patch below, it seems that the read() command may fail
> to receive a response, even when increasing the retry times. It never gets
> a response when it fails.
> 
> fbf84fb368923 ("UBUNTU: SAUCE: platform/x86: dell-uart-backlight: replace chars_in_buffer() with flush_chars()")
> 
> To fix this, try adding a small delay after the write() function as a
> workaround.
> 
> [Test case]
> 1. Add dell_uart_backlight.dyndbg="+pt" to the kernel cmdline
> 2. Boots up the system and check dmesg
> 3. Make sure there is no dell_uart_backlight rx NULL message in dmesg
> 4. Try to unload/reload dell_uart_backlight couple times and check dmesg again
> 
> [Where problems could occur]
> sleep for 1ms is pretty short that it's not possible to lead to messages loss.
> 
> Chia-Lin Kao (AceLan) (1):
>    UBUNTU: SAUCE: platform/x86: dell-uart-backlight: add small delay
>      after write command
> 
>   drivers/platform/x86/dell/dell-uart-backlight.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 

Rejected for the following reasons:
- the bug reference (no longer?) seems to work
- and while fixing above by re-submitting I would adjust the 
justification (in bug
   report and cover email) to give a short explanation in the fix 
section why this
   is SAUCE for a SRU (temporary work around, still working on better 
solution)

-Stefan
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