linux-kernel - Re: [PATCH v3 5/5] mtd: spi-nor: cadence-quadspi: Add runtime PM support

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Date:   Tue, 26 Sep 2017 01:49:46 +0200
From:   Marek Vasut <marek.vasut@...il.com>
To:     matthew.gerlach@...ux.intel.com
Cc:     Vignesh R <vigneshr@...com>,
        Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Rob Herring <robh+dt@...nel.org>,
        linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 5/5] mtd: spi-nor: cadence-quadspi: Add runtime PM
 support

On 09/26/2017 12:41 AM, matthew.gerlach@...ux.intel.com wrote:
> 
> 
> On Sun, 24 Sep 2017, Marek Vasut wrote:
> 
>> On 09/24/2017 03:27 PM, Vignesh R wrote:
>>>
>>>
>>> On 9/24/2017 6:42 PM, Marek Vasut wrote:
>>>> On 09/24/2017 03:08 PM, Vignesh R wrote:
>>>>>
>>>>>
>>>>> On 9/24/2017 5:31 PM, Marek Vasut wrote:
>>>>>> On 09/24/2017 12:59 PM, Vignesh R wrote:
>>>>>>> Add pm_runtime* calls to cadence-quadspi driver. This is required to
>>>>>>> switch on QSPI power domain on TI 66AK2G SoC during probe.
>>>>>>>
>>>>>>> Signed-off-by: Vignesh R <vigneshr@...com>
>>>>>>
>>>>>> Are you planning to add some more fine-grained PM control later?
>>>>>
>>>>> Yes, I will need to add fine-grained PM control at some point. But,
>>>>> for
>>>>> now SoC does not really support low power mode or runtime power saving
>>>>> option.
>>>>> The fact that driver still uses clk_prepare_*() calls to
>>>>> enable/disable
>>>>> clocks instead of pm_*() calls makes it a bit tricky though.
>>>>>
>>>>> Just figured out I forgot to add cleanup code in error handling
>>>>> path of
>>>>> probe(). Will fix that and send a v4.
>>>>
>>>> OK, fine. Cleanups are welcome. The SoCFPGA doesn't do much runtime PM
>>>> either, so it's fine for now.
>>>>
>>>
>>> Ok thanks! Do you know if pm_runtime_get_sync() can enable clocks for
>>> QSPI on SoCFPGA or if clk_prepare_enable() is needed? Just trying to see
>>> if its possible to get rid of clk_*() calls in favor of pm_*() calls.
>>
>> Not of the top of my head, sorry. +CC Matthew, he should know.
> 
> I am not an expert at the clock framework nor the power management, but I
> did ask around a bit.  No one I asked was planning to change the clk_*()
> calls to pm_*() call, but the feedback was that it would be a good idea.

The question is, if we do the replacement, will it break on socfpga ?
A quick test might be useful.

-- 
Best regards,
Marek Vasut