linux-kernel - Re: [PATCH] ARM: dts: da850-evm: add clock properties to the nand node

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Date:   Tue, 6 Feb 2018 12:16:48 -0600
From:   David Lechner <david@...hnology.com>
To:     Sekhar Nori <nsekhar@...com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Cc:     Bartosz Golaszewski <brgl@...ev.pl>,
        Kevin Hilman <khilman@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        arm-soc <linux-arm-kernel@...ts.infradead.org>,
        linux-devicetree <devicetree@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: dts: da850-evm: add clock properties to the nand
 node

On 02/06/2018 07:51 AM, Sekhar Nori wrote:
> On Tuesday 06 February 2018 06:38 PM, Bartosz Golaszewski wrote:
>> 2018-02-06 12:07 GMT+01:00 Sekhar Nori <nsekhar@...com>:
>>> On Monday 05 February 2018 09:22 PM, Bartosz Golaszewski wrote:
>>>> From: Bartosz Golaszewski <bgolaszewski@...libre.com>
>>>>
>>>> Make nand work with the common clock framework by specifying which
>>>> clock should be used and what name to look up.
>>>>
>>>> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
>>>> ---
>>>>   arch/arm/boot/dts/da850-evm.dts | 3 +++
>>>>   1 file changed, 3 insertions(+)
>>>>
>>>> diff --git a/arch/arm/boot/dts/da850-evm.dts b/arch/arm/boot/dts/da850-evm.dts
>>>> index a86a8a1816f2..2602ad8e99ee 100644
>>>> --- a/arch/arm/boot/dts/da850-evm.dts
>>>> +++ b/arch/arm/boot/dts/da850-evm.dts
>>>> @@ -296,6 +296,9 @@
>>>>                        reg = <0 0x02000000 0x02000000
>>>>                               1 0x00000000 0x00008000>;
>>>>
>>>> +                     clocks = <&psc0 3>;
>>>> +                     clock-names = "aemif";
>>>
>>> Looks like this is being added only to satisfy the devm_clk_get() call
>>> in nand_davinci_probe() which I think is superfluous since we also
>>> enable the same clock in aemif_probe().
>>>
>>> Perhaps the better solution is to drip the clk code in
>>> drivers/mtd/nand/davinci_nand.c and shift legacy code to start using
>>> drivers/memory/aemif.c as well? This way we can also drop
>>> arch/arm/mach-davinci/aemif.c
>>>
>>> Thanks,
>>> Sekhar
>>
>> Yes, this sounds good, but I think we should leave it for later as an
>> additional improvement, once everything else is in place. I think
>> these patches should be applied together with David's series in order
>> to not break the support on davinci boards and the aemif work would go
>> in later as a follow-up. How about that?
> 
> No, I dont think we should add temporary hacks to DT to work around
> driver issues (I do think its a hack since the clock belongs to aemif
> module not NAND flash).
> 
> An easier driver hack might be to not treat devm_clk_get() failure in
> davinci_nand.c as catastrophic. It will safely fail in DT case and we
> should get the clock in legacy boot case.
> 
> I think we are looking at a driver update dependency anyway.

It looks like keystone.dtsi is using the clock-ranges property in the
aemif node to pass the clock to child nodes. Could we not do the same
in da850.dtsi?

> 
>>
>> Also: I don't have any keystone board to test whether such changes
>> don't break the nand support there. Would you be able to test this?
> 
> Yes, I have access to those boards.
> 
> Thanks,
> Sekhar
>