From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thierry Reding Subject: Re: [PATCH v1] drm/tegra: dpaux: Fix always-failing probing of the driver Date: Mon, 24 Sep 2018 15:36:29 +0200 Message-ID: <20180924133629.GD23547@ulmo> References: <20180921114241.17002-1-digetx@gmail.com> <20180924115907.GW21032@ulmo> <3ccda930-8ec1-00b0-54e0-c689e7ee4b62@nvidia.com> <3148e42b-70cf-a7b4-a644-b969f61724d6@gmail.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============0695242135==" Return-path: In-Reply-To: <3148e42b-70cf-a7b4-a644-b969f61724d6@gmail.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: Dmitry Osipenko Cc: linux-tegra@vger.kernel.org, dri-devel@lists.freedesktop.org, Jon Hunter List-Id: linux-tegra@vger.kernel.org --===============0695242135== Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="uxuisgdDHaNETlh8" Content-Disposition: inline --uxuisgdDHaNETlh8 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Sep 24, 2018 at 03:40:35PM +0300, Dmitry Osipenko wrote: > On 9/24/18 3:32 PM, Jon Hunter wrote: > >=20 > > 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. > > > >=20 > > > > Fixes: 0751bb5c44fe ("drm/tegra: dpaux: Add pinctrl support") > > > > Cc: # v4.8+ > > > > Signed-off-by: Dmitry Osipenko > > > > --- > > > >=20 > > > > 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. Thi= erry, > > > > please take a closer look at this driver and test it thoroughly, it= has > > > > some obvious problems. > > > >=20 > > > > drivers/gpu/drm/tegra/dpaux.c | 2 +- > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > >=20 > > > 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. > > > =3D) > > >=20 > > > 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. > > >=20 > > > >=20 > > > > 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_de= vice *pdev) > > > > * is no possibility to perform the I2C mode configuration in the > > > > * HDMI path. > > > > */ > > > > - err =3D tegra_dpaux_pad_config(dpaux, DPAUX_HYBRID_PADCTL_MODE_I2= C); > > > > + err =3D tegra_dpaux_pad_config(dpaux, DPAUX_PADCTL_FUNC_I2C); > > > > if (err < 0) > > > > return err; > > >=20 > > > If you look at the definitions of both DPAUX_HYBRID_PADCTL_MODE_I2C a= nd > > > DPAUX_PADCTL_FUNC_I2C, you'll see that both are actually the same, wh= ich > > > is a good explanation for why the driver performs flawlessly. > > >=20 > > > That said, your change is obviously correct. I've applied it, but sin= ce > > > 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. > >=20 > > Did you change the subject for the patch because as you mentioned it > > does not seem related to the change? > >=20 > > Otherwise for the fix you can have my ... > >=20 > > Acked-by: Jon Hunter > >=20 > > 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. >=20 > Guy with nickname "vlado" said on the IRC that the panel stopped to work = on > T124 chromebook since 4.16 kernel, reverting commit [0] helps. >=20 > [0] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/c= ommit/drivers/gpu/drm/drm_dp_helper.c?id=3D17ab7806de0c10d27cdbda8ef57ca680= bdd24315 I'm pretty sure that's something that we fixed, but I'll have to check. Is this patch reported to help with that issue, or where's the connection? 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