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

[Thierry Reding <thierry.reding@gmail.com>]

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On Mon, Sep 24, 2018 at 01:32:41PM +0100, Jon Hunter wrote:
> 
> 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@vger.kernel.org> # v4.8+
> >> Signed-off-by: Dmitry Osipenko <digetx@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?

Yes, I did.

> Otherwise for the fix you can have my ...
> 
> Acked-by: Jon Hunter <jonathanh@nvidia.com>

Added, thanks.

Thierry

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