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

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Message-ID: <aefa4c12-e976-3a0e-851c-0433a751521d@st.com>
Date:   Thu, 5 Apr 2018 14:00:23 +0000
From:   Patrice CHOTARD <patrice.chotard@...com>
To:     Hans de Goede <hdegoede@...hat.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>,
        Tejun Heo <tj@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>
CC:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "linux-ide@...r.kernel.org" <linux-ide@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH] ata: ahci-platform: add reset control support

Hi Hans

On 04/05/2018 03:27 PM, Hans de Goede wrote:
> Hi,
> 
> On 05-04-18 15:17, Patrice CHOTARD wrote:
>> 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@...ionext.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.
> 
> So in your case you might be able to remove the reset handling
> from the ahci_st driver and rely on the new libahci_platform
> handling instead? If that works that seems like a win to me.

Yes, I did a quick test, the reset handling can be removed from our driver.

Patrice
> 
> As said elsewhere in this thread I think it makes sense to keep (or re-add
> after a revert) the libahci_platform reset code, but make it conditional
> on a flag passed to ahci_platform_get_resources(). This way we get
> the shared code for most cases and platforms which need special handling
> can opt-out.
> 
> Regards,
> 
> Hans
> 
> 
>>
>> 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