linux-kernel - Re: [PATCH] spi: Fix error code checking in spi_mem_exec

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Message-ID: <493cdb11-72b7-4d03-b982-448451fd5824@broadcom.com>
Date: Wed, 13 Mar 2024 13:06:35 -0700
From: Florian Fainelli <florian.fainelli@...adcom.com>
To: Pratyush Yadav <pratyush@...nel.org>
Cc: Michael Walle <mwalle@...nel.org>, linux-spi@...r.kernel.org,
 Mark Brown <broonie@...nel.org>, Miquel Raynal <miquel.raynal@...tlin.com>,
 Mika Westerberg <mika.westerberg@...ux.intel.com>,
 "Chia-Lin Kao (AceLan)" <acelan.kao@...onical.com>,
 open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] spi: Fix error code checking in spi_mem_exec_op()

On 3/13/24 12:34, Florian Fainelli wrote:
> On 3/13/24 12:29, Pratyush Yadav wrote:
>> On Wed, Mar 13 2024, Florian Fainelli wrote:
>>
>>> On 3/13/24 11:28, Pratyush Yadav wrote:
>>>> On Wed, Mar 13 2024, Michael Walle wrote:
>>>>
>>>>> On Wed Mar 13, 2024 at 6:10 PM CET, Florian Fainelli wrote:
>>>>>> After commit cff49d58f57e ("spi: Unify error codes by replacing 
>>>>>> -ENOTSUPP with
>>>>>> -EOPNOTSUPP"), our SPI NOR flashes would stop probing with the 
>>>>>> following
>>>>>> visible in the kernel log:
>>>>>>
>>>>>> [    2.196300] brcmstb_qspi f0440920.qspi: using bspi-mspi mode
>>>>>> [    2.210295] spi-nor: probe of spi1.0 failed with error -95
>>>>>>
>>>>>> It turns out that the check in spi_mem_exec_op() was changed to check
>>>>>> for -ENOTSUPP (old error code) or -EOPNOTSUPP (new error code), 
>>>>>> but this
>>>>>> means that for drivers that were converted, the second condition 
>>>>>> is now
>>>>>> true, and we stop falling through like we used to. Fix the error to
>>>>>> check for neither error being neither -ENOTSUPP *nor* -EOPNOTSUPP.
>>>>>>
>>>>>> Fixes: cff49d58f57e ("spi: Unify error codes by replacing 
>>>>>> -ENOTSUPP with -EOPNOTSUPP")
>>>>>> Signed-off-by: Florian Fainelli <florian.fainelli@...adcom.com>
>>>>>> Change-Id: I4159811f6c582c4de2143382473d2000b8755872
>>>>>
>>>>> Ha, thank you!
>>>>>
>>>>> Reviewed-by: Michael Walle <mwalle@...nel.org>
>>>>>
>>>>> FWIW in next, there is commit
>>>>> e63aef9c9121e ("spi: spi-mem: add statistics support to ->exec_op() 
>>>>> calls")
>>>>> that probably will conflict with this one.
>>>>>
>>>>> Also, - not for this patch - but with that logic, spi_mem_exec_op()
>>>>> might return EOPNOTSUPP *or* ENOTSUPP, even for drivers which might
>>>>> still return ENOTSUPP, because there is one condition in
>>>>> spi_mem_exec_op() which will always return EOPNOTSUPP. That is
>>>>> somewhat confusing, no?
>>>> I agree. I suppose it would be better to do:
>>>>       if (!ret)
>>>>          return 0;
>>>>       if (ret == -ENOTSUPP || ret == -EOPNOTSUPP)
>>>>          return -EOPNOTSUPP;
>>>>
>>>
>>> But with e63aef9c9121e ("spi: spi-mem: add statistics support to 
>>> ->exec_op()
>>> calls") applied, would not that mean duplicating the statistics 
>>> gathering, or
>>> were the statistics gathering only intended for when ret == 0?
>>
>> Hmm, I didn't properly understand this. Ignore my suggestion. Your patch
>> does the right thing.
> 
> What I meant is that e63aef9c9121e will increment statistics not just 
> when we return 0 from ctlr->mem_ops->exec_op, but also if we return 
> -ENOTSUPP or -EOPNOTSUPP, and I am  not sure if this is exactly what is 
> intended. But this is somewhat orthogonal.

It looks like the handling of a non-zero return code will fall either in 
the -ETIMEDOUT category, or in the general category of an error. I 
suppose there is a question whether a operation that could not be 
supported should fall in the "error" category.
-- 
Florian


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