Re: [RFC][PATCH] spi: Setup the master controller driver before setting the chipselect

[Franklin S Cooper Jr.]

On 10/14/2015 06:45 AM, Heiner Kallweit wrote:
> On Wed, Oct 14, 2015 at 1:08 PM, Andy Shevchenko
> <andy.shevchenko@xxxxxxxxx> wrote:
>> +Cc: Jarkko to see from spi-pxa2xx prospective
>>
>> On Wed, Oct 14, 2015 at 12:47 PM, Ivan T. Ivanov <iivanov.xz@xxxxxxxxx> wrote:
>>> Adding Andy.
>>>
>>>
>>>> On Oct 13, 2015, at 12:01 AM, Franklin S Cooper Jr <fcooper@xxxxxx> wrote:
>>>>
>>>> Some devices depend on the master controller driver setup function being
>>>> called before calling any chipselect functions.
>>>>
>>>> Insure that this is done otherwise uninitialized structures may be
>>>> accessed causing a kernel panic.
>> As far as I understand my concern should be about spi-dw driver.
>>
>> So, I have just tested yesterday's linux-next with and without
>> proposed patch. Works for me:
>> Tested-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
>>
>>>> Signed-off-by: Franklin S Cooper Jr <fcooper@xxxxxx>
>>>> ---
>>>> drivers/spi/spi.c | 4 ++--
>>>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
>>>> index 38006cc..9374d82 100644
>>>> --- a/drivers/spi/spi.c
>>>> +++ b/drivers/spi/spi.c
>>>> @@ -2053,11 +2053,11 @@ int spi_setup(struct spi_device *spi)
>>>>       if (!spi->max_speed_hz)
>>>>               spi->max_speed_hz = spi->master->max_speed_hz;
>>>>
>>>> -     spi_set_cs(spi, false);
>>>> -
>>>>       if (spi->master->setup)
>>>>               status = spi->master->setup(spi);
>>>>
>>>> +     spi_set_cs(spi, false);
>>>> +
>>>>       dev_dbg(&spi->dev, "setup mode %d, %s%s%s%s%u bits/w, %u Hz max --> %d\n",
>>>>                       (int) (spi->mode & (SPI_CPOL | SPI_CPHA)),
>>>>                       (spi->mode & SPI_CS_HIGH) ? "cs_high, " : "",
>>>> --
>>>> 2.6.1
>>>>
>>>> --
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>>
>>
>> --
>> With Best Regards,
>> Andy Shevchenko
>> --
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> The recent change to the bitbang driver leads to the the set_cs hook
> of spi_master being set
> now for all drivers using the bitbang layer. This hook is called also
> from spi_setup and therefore
> one possible side effect is issues with bitbang drivers implementing
> the chipselect hook of
> spi_bitbang with a dependency on the master being set up before.
> The proposed patch looks good to me.
> There should be no impact on drivers not using bitbang.
Thank all. Since nothing obvious seems wrong with this patch I will resend this patch without the RFC.


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