On 4/27/22 14:39, Ulf Hansson wrote:
On Wed, 27 Apr 2022 at 20:09, Kamal Dasu <kdasu.kdev@xxxxxxxxx> wrote:
From: Al Cooper <alcooperx@xxxxxxxxx>
Enabling this feature will allow the controller to stop the bus
clock when the bus is idle. The feature is not part of the standard
and is unique to newer Arasan cores and is enabled with a bit in a
vendor specific register. This feature will only be enabled for
non-removable devices because they don't switch the voltage and
clock gating breaks SD Card volatge switching.
Rather than using a HW specific thing for this, it may be better to
use runtime PM. There are plenty of examples to get inspired from, so
it should be rather easy to implement, I think. More importantly, it
should work for both (e)MMC and SD cards, unless there are some
specific things to manage for this controller.
When it comes to SDIO, some driver simply bumps the runtime PM usage
count (pm_runtime_get_noresume()) to prevent the device from being
runtime suspended. There are ways to work around this, let me know if
you need some guidance around how to fix that too.
That said, I am not entirely opposed to $subject patch, but I wanted
to point out that there are better alternatives.
This is a good suggestion, I would not consider runtime PM and enabling
the clock gating as being alternatives to one another, but rather
complementary.
--
Florian
