[PATCH] ata: ahci-platform: add reset control support

[Patrice CHOTARD]

Hi Thierry

On 04/05/2018 11:54 AM, Thierry Reding wrote:
> On Fri, Mar 23, 2018 at 10:30:53AM +0900, Kunihiko Hayashi wrote:
>> Add support to get and control a list of resets for the device
>> as optional and shared. These resets must be kept de-asserted until
>> the device is enabled.
>>
>> This is specified as shared because some SoCs like UniPhier series
>> have common reset controls with all ahci controller instances.
>>
>> Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko at socionext.com>
>> ---
>>   .../devicetree/bindings/ata/ahci-platform.txt      |  1 +
>>   drivers/ata/ahci.h                                 |  1 +
>>   drivers/ata/libahci_platform.c                     | 24 +++++++++++++++++++---
>>   3 files changed, 23 insertions(+), 3 deletions(-)
> 
> This causes a regression on Tegra because we explicitly request the
> resets after the call to ahci_platform_get_resources().

I confirm, we got exactly the same behavior on STi platform.

> 
>  From a quick look, ahci_mtk and ahci_st are in the same boat, adding the
> corresponding maintainers to Cc.
> 
> Patrice, Matthias: does SATA still work for you after this patch? This
> has been in linux-next since next-20180327.

SATA is still working after this patch, but a kernel warning is 
triggered due to the fact that resets are both requested by 
libahci_platform and by ahci_st driver.

Patrice

> 
> Given how this is one of the more hardware-specific bits, perhaps a
> better way to do this is to move reset handling into a Uniphier driver
> much like Tegra, Mediatek and ST?
> 
> That said, I don't see SATA support for any of the Socionext hardware
> either in the DT bindings or drivers/ata, so perhaps it'd be best to
> back this out again until we have something that's more well tested?
> 
> Thierry
>