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

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Message-ID: <54dbdb98-e0e4-c8c9-fec4-2f050745d9be@ti.com>
Date:   Tue, 6 Feb 2018 19:21:54 +0530
From:   Sekhar Nori <nsekhar@...com>
To:     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>,
        David Lechner <david@...hnology.com>,
        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 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.

> 
> 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