From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jernej =?utf-8?B?xaBrcmFiZWM=?= Subject: Re: Re: [PATCH v2 11/27] drm/sun4i: tcon: Add support for tcon-top gate Date: Fri, 15 Jun 2018 19:33:53 +0200 Message-ID: <3871160.F3Km1rQkUz@jernej-laptop> References: <20180612200036.21483-1-jernej.skrabec@siol.net> <2948115.KggauuSURZ@jernej-laptop> Reply-To: jernej.skrabec-gGgVlfcn5nU@public.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Return-path: Sender: linux-sunxi-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org In-Reply-To: List-Post: , List-Help: , List-Archive: , List-Unsubscribe: , To: Chen-Yu Tsai Cc: Maxime Ripard , Rob Herring , David Airlie , Gustavo Padovan , Maarten Lankhorst , Sean Paul , Mark Rutland , dri-devel , devicetree , linux-arm-kernel , linux-kernel , linux-clk , linux-sunxi List-Id: devicetree@vger.kernel.org Dne petek, 15. junij 2018 ob 19:13:17 CEST je Chen-Yu Tsai napisal(a): > On Sat, Jun 16, 2018 at 12:41 AM, Jernej =C5=A0krabec >=20 > wrote: > > Hi, > >=20 > > Dne petek, 15. junij 2018 ob 10:31:10 CEST je Maxime Ripard napisal(a): > >> Hi, > >>=20 > >> On Tue, Jun 12, 2018 at 10:00:20PM +0200, Jernej Skrabec wrote: > >> > TV TCONs connected to TCON TOP have to enable additional gate in ord= er > >> > to work. > >> >=20 > >> > Add support for such TCONs. > >> >=20 > >> > Signed-off-by: Jernej Skrabec > >> > --- > >> >=20 > >> > drivers/gpu/drm/sun4i/sun4i_tcon.c | 11 +++++++++++ > >> > drivers/gpu/drm/sun4i/sun4i_tcon.h | 4 ++++ > >> > 2 files changed, 15 insertions(+) > >> >=20 > >> > diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c > >> > b/drivers/gpu/drm/sun4i/sun4i_tcon.c index 08747fc3ee71..0afb5a94a41= 4 > >> > 100644 > >> > --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c > >> > +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c > >> > @@ -688,6 +688,16 @@ static int sun4i_tcon_init_clocks(struct device > >> > *dev, > >> >=20 > >> > dev_err(dev, "Couldn't get the TCON bus clock\n"); > >> > return PTR_ERR(tcon->clk); > >> > =20 > >> > } > >> >=20 > >> > + > >> > + if (tcon->quirks->has_tcon_top_gate) { > >> > + tcon->top_clk =3D devm_clk_get(dev, "tcon-top"); > >> > + if (IS_ERR(tcon->top_clk)) { > >> > + dev_err(dev, "Couldn't get the TCON TOP bus > >> > clock\n"); > >> > + return PTR_ERR(tcon->top_clk); > >> > + } > >> > + clk_prepare_enable(tcon->top_clk); > >> > + } > >> > + > >>=20 > >> Is it required for the TCON itself to operate, or does the TCON > >> requires the TCON TOP, which in turn requires that clock to be > >> functional? > >>=20 > >> I find it quite odd to have a clock that isn't meant for a particular > >> device to actually be wired to another device. I'm not saying this > >> isn't the case, but it would be a first. > >=20 > > Documentation doesn't say much about that gate. I did few tests and TCO= N > > registers can be read and written even if TCON TOP TV TCON gate is > > disabled. However, there is no image, as expected. >=20 > The R40 manual does include it in the diagram, on page 504. There's also = a > mux to select whether the clock comes directly from the CCU or the TV > encoder (a feedback mode?). I assume this is the gate you are referring t= o > here, in which case it is not a bus clock, but rather the TCON module or > channel clock, strangely routed. >=20 > > More interestingly, I enabled test pattern directly in TCON to eliminat= e > > influence of the mixer. As soon as I disabled that gate, test pattern o= n > > HDMI screen was gone, which suggest that this gate influences something > > inside TCON. > >=20 > > Another test I did was that I moved enable/disable gate code to > > sun4i_tcon_channel_set_status() and it worked just as well. > >=20 > > I'll ask AW engineer what that gate actually does, but from what I saw,= I > > would say that most appropriate location to enable/disable TCON TOP TV > > TCON > > gate is TCON driver. Alternatively, TCON TOP driver could check if any = TV > > TCON is in use and enable appropriate gate. However, that doesn't sound > > right to me for some reason. >=20 > If what I said above it true, then yes, the appropriate location to enabl= e > it is the TCON driver, but moreover, the representation of the clock tree > should be fixed such that the TCON takes the clock from the TCON TOP as i= ts > channel/ module clock instead. That way you don't need this patch, but > you'd add another for all the clock routing. Can you be more specific? I not sure what you mean here. Best regards, Jernej --=20 You received this message because you are subscribed to the Google Groups "= linux-sunxi" group. To unsubscribe from this group and stop receiving emails from it, send an e= mail to linux-sunxi+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit https://groups.google.com/d/optout.