[PATCH v1] drm/tegra: dpaux: Fix always-failing probing of the driver

[Jon Hunter]

On 24/09/18 12:59, Thierry Reding wrote:
> On Fri, Sep 21, 2018 at 02:42:41PM +0300, Dmitry Osipenko wrote:
>> Some of definitions in the code changed the meaning, unfortunately one
>> place missed the change.
>>
>> Fixes: 0751bb5c44fe ("drm/tegra: dpaux: Add pinctrl support")
>> Cc: <stable at vger.kernel.org> # v4.8+
>> Signed-off-by: Dmitry Osipenko <digetx at gmail.com>
>> ---
>>
>> I don't have HW to test DPAUX driver, apparently it has been broken for
>> 2+ years now. There is also a known issue on with the DPAUX driver that
>> prevents it from probing, that was discussed on the #tegra IRC. Thierry,
>> please take a closer look at this driver and test it thoroughly, it has
>> some obvious problems.
>>
>>  drivers/gpu/drm/tegra/dpaux.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> It's odd that you claim that the driver is always failing probe and at
> the same time you say that you don't have hardware to test the driver.
> =)
> 
> I know for a fact that this driver does not usually fail because it is
> required on all recent chips (Tegra210 and later) to drive HDMI, which
> we support on all boards, so it is indeed thoroughly tested.
> 
>>
>> diff --git a/drivers/gpu/drm/tegra/dpaux.c b/drivers/gpu/drm/tegra/dpaux.c
>> index d84e81ff36ad..ba5681fab73b 100644
>> --- a/drivers/gpu/drm/tegra/dpaux.c
>> +++ b/drivers/gpu/drm/tegra/dpaux.c
>> @@ -521,7 +521,7 @@ static int tegra_dpaux_probe(struct platform_device *pdev)
>>  	 * is no possibility to perform the I2C mode configuration in the
>>  	 * HDMI path.
>>  	 */
>> -	err = tegra_dpaux_pad_config(dpaux, DPAUX_HYBRID_PADCTL_MODE_I2C);
>> +	err = tegra_dpaux_pad_config(dpaux, DPAUX_PADCTL_FUNC_I2C);
>>  	if (err < 0)
>>  		return err;
>>  
> 
> If you look at the definitions of both DPAUX_HYBRID_PADCTL_MODE_I2C and
> DPAUX_PADCTL_FUNC_I2C, you'll see that both are actually the same, which
> is a good explanation for why the driver performs flawlessly.
> 
> That said, your change is obviously correct. I've applied it, but since
> it doesn't actually fix anything, and doesn't change anything from a
> binary point of view, I've removed the Fixes: and Cc: stable tags.

Did you change the subject for the patch because as you mentioned it
does not seem related to the change?

Otherwise for the fix you can have my ...

Acked-by: Jon Hunter <jonathanh at nvidia.com>

The dpaux driver has been working fine for me on Tegra210 Smaug when
using the pins for I2C and I have not seen any probing problems.

Cheers
Jon

-- 
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