[Intel-gfx] [PATCH v3 1/3] drm: Stop spamming log with drm_cache message

[Lucas De Marchi]

On Tue, Feb 01, 2022 at 09:12:05AM -0800, Jose Souza wrote:
>On Mon, 2022-01-31 at 08:59 -0800, Lucas De Marchi wrote:
>> Only x86 and in some cases PPC have support added in drm_cache.c for the
>> clflush class of functions. However warning once is sufficient to taint
>> the log instead of spamming it with "Architecture has no drm_cache.c
>> support" every few millisecond. Switch to WARN_ONCE() so we still get
>> the log message, but only once, together with the warning. E.g:
>>
>> 	------------[ cut here ]------------
>> 	Architecture has no drm_cache.c support
>> 	WARNING: CPU: 80 PID: 888 at drivers/gpu/drm/drm_cache.c:139 drm_clflush_sg+0x40/0x50 [drm]
>> 	...
>>
>> v2 (Jani): use WARN_ONCE() and keep the message previously on pr_err()
>
>Reviewed-by: José Roberto de Souza <jose.souza at intel.com>
>
>But while at it, why not add a drm_device parameter to this function so we can use drm_WARN_ONCE()?
>Anyways, it is better than before.

I thought about that, but it didn't seem justifiable because:

1) drm_WARN_ONCE will basically add dev_driver_string() to the log.
However the warning message here is basically helping the bootstrap of
additional archs. They shouldn't be seen on anything properly supported.

2) This seems all to be a layer below drm anyway and could even be used
in places outside easy access to a drm pointer.

So, it seems the benefit of using the subsystem-specific drm_WARN_ONCE
doesn't justify the hassle of changing the callers, possibly adding
additional back pointers to have access to the drm device pointer.

thanks
Lucas De Marchi