On Wed, Jun 10, 2026 at 05:40:56PM +0300, Svyatoslav Ryhel wrote:

вт, 9 черв. 2026 р. о 22:17 Andy Shevchenko [off-list ref] пише:

quoted

On Sat, Jun 06, 2026 at 07:57:34AM +0300, Svyatoslav Ryhel wrote:

quoted

Missing coherent_dma_mask assigning triggers the following warning in
dmesg:

[    3.287872] platform lm3533-backlight.0: DMA mask not set

Since this warning might be elevated to an error in the future, set
coherent_dma_mask to zero because both the core and cells do not utilize
DMA.

Hmm... I am not sure about this. The entire kernel has only two drivers that
do that, and thanks to their commit messages one of them pointed out to the
commit from 2018. So, if no other devices suffer from this, I think it has to
be a better way of achieving the same.

If mfd framework warns that DMA mask is not set then this must be
addressed. Why then there is such warning at the first place if mask
can be just skipped. Then warning would be just a debug message. What
is warning today can become error tomorrow.

It's there for 8 years. And only a few drivers explicitly nullify it.
I think doing this patch one should really understand what's going on.
(Note, I'm not that person, it's my gut feelings based on the experience
 and the above statistics.) MFD creates a lot of platform devices for
which DMA mask is set automatically. So, why is it not set properly for
this device?

-- 
With Best Regards,
Andy Shevchenko