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Mon, 25 Jun 2018 01:00:19 -0700 (PDT) From: Jernej =?utf-8?B?xaBrcmFiZWM=?= To: linux-sunxi@googlegroups.com, wens@csie.org 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 Subject: Re: [linux-sunxi] Re: [PATCH v2 11/27] drm/sun4i: tcon: Add support for tcon-top gate Date: Mon, 25 Jun 2018 09:58:57 +0200 Message-ID: <1797170.duyCyYzgBk@jernej-laptop> In-Reply-To: References: <20180612200036.21483-1-jernej.skrabec@siol.net> <4758026.sMRKe6aTTs@jernej-laptop> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Dne ponedeljek, 25. junij 2018 ob 05:51:41 CEST je Chen-Yu Tsai napisal(a): > On Mon, Jun 25, 2018 at 3:52 AM, Jernej =C5=A0krabec >=20 > wrote: > > Dne =C4=8Detrtek, 21. junij 2018 ob 17:35:45 CEST je Jernej =C5=A0krabe= c napisal(a): > >> Dne =C4=8Detrtek, 21. junij 2018 ob 03:23:27 CEST je Chen-Yu Tsai napi= sal(a): > >> > On Thu, Jun 21, 2018 at 3:37 AM, Jernej =C5=A0krabec > >> > > >>=20 > >> wrote: > >> > > Dne sobota, 16. junij 2018 ob 07:48:38 CEST je Chen-Yu Tsai=20 napisal(a): > >> > >> On Sat, Jun 16, 2018 at 1:33 AM, Jernej =C5=A0krabec > >> > >> > >> > >=20 > >> > > wrote: > >> > >> > Dne petek, 15. junij 2018 ob 19:13:17 CEST je Chen-Yu Tsai > >=20 > > 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 > >>=20 > >> napisal(a): > >> > >> >> >> Hi, > >> > >> >> >>=20 > >> > >> >> >> On Tue, Jun 12, 2018 at 10:00:20PM +0200, Jernej Skrabec=20 wrote: > >> > >> >> >> > TV TCONs connected to TCON TOP have to enable additional > >> > >> >> >> > gate > >> > >> >> >> > in > >> > >> >> >> > order > >> > >> >> >> > 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..0afb5a94a414 > >> > >> >> >> > 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 T= OP > >> > >> >> >> > 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 sayi= ng > >> > >> >> >> this > >> > >> >> >> isn't the case, but it would be a first. > >> > >> >> >=20 > >> > >> >> > Documentation doesn't say much about that gate. I did few te= sts > >> > >> >> > and > >> > >> >> > TCON > >> > >> >> > registers can be read and written even if TCON TOP TV TCON g= ate > >> > >> >> > 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 > >> > >> >> to > >> > >> >> 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 > >> > >> >> > eliminate > >> > >> >> > influence of the mixer. As soon as I disabled that gate, test > >> > >> >> > pattern > >> > >> >> > on > >> > >> >> > 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 T= CON > >> > >> >> > TOP > >> > >> >> > TV > >> > >> >> > TCON > >> > >> >> > gate is TCON driver. Alternatively, TCON TOP driver could ch= eck > >> > >> >> > 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 locati= on > >> > >> >> to > >> > >> >> enable > >> > >> >> 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 TC= ON > >> > >> >> TOP > >> > >> >> as > >> > >> >> its > >> > >> >> channel/ module clock instead. That way you don't need this > >> > >> >> patch, > >> > >> >> but > >> > >> >> you'd add another for all the clock routing. > >> > >> >=20 > >> > >> > Can you be more specific? I not sure what you mean here. > >> > >>=20 > >> > >> For clock related properties in the device tree: > >> > >>=20 > >> > >> &tcon_top { > >> > >>=20 > >> > >> clocks =3D <&ccu CLK_BUS_TCON_TOP>, > >> > >> =20 > >> > >> <&ccu CLK_TCON_TV0>, > >> > >> <&tve0>, > >> > >> <&ccu CLK_TCON_TV1>, > >> > >> <&tve1>; > >> > >> =20 > >> > >> clock-names =3D "bus", "tcon-tv0", "tve0", "tcon-tv1", "tve1"; > >> > >> clock-output-names =3D "tcon-top-tv0", "tcon-top-tv1"; > >> > >>=20 > >> > >> }; > >> > >>=20 > >> > >> &tcon_tv0 { > >> > >>=20 > >> > >> clocks =3D <&ccu CLK_BUS_TCON_TV0>, <&tcon_top 0>' > >> > >> clock-names =3D "ahb", "tcon-ch1"; > >> > >>=20 > >> > >> }; > >> > >>=20 > >> > >> A diagram would look like: > >> > >> | This part is TCON TOP | > >> > >> =20 > >> > >> v v > >> > >>=20 > >> > >> CCU CLK_TCON_TV0 --|----\ | > >> > >>=20 > >> > >> | mux ---- gate ----|-- TCON_TV0 > >> > >>=20 > >> > >> TVE0 --------------|----/ | > >> > >>=20 > >> > >> And the same goes for TCON_TV1 and TVE1. > >> > >>=20 > >> > >> The user manual is a bit lacking on how TVE outputs a clock thoug= h. > >> > >=20 > >> > > I didn't yet received any response on HW details from AW till now, > >> > > but I > >> > > would like to post new version of patches soon. > >> > >=20 > >> > > While chaining like you described could be implemented easily, I > >> > > don't > >> > > think it really represents HW as it is. Tests showed that these two > >> > > clocks are independent, otherwise register writes/reads wouldn't be > >> > > possible with tcon- top gate disabled. I chose tcon-top bus clock = as > >> > > a > >> > > parent becase if it is not enabled, it simply won't work. > >> >=20 > >> > AFAIK with the TCONs, even when the TCON channel clock (not the bus > >> > clock) > >> > is disabled, register accesses still work. > >>=20 > >> You're right, I just tested that. > >>=20 > >> > I'm saying that the TCON TOP > >> > gate is downstream from the TCON channel clock in the CCU. These are > >> > not > >> > related to the TCON bus clock in the CCU, which affects register > >> > access. > >> >=20 > >> > Did Allwinner provide any information regarding the hierarchy of the > >> > clocks? > >>=20 > >> No reponse for now. > >>=20 > >> > > However, if everyone feels chaining is the best way to implement i= t, > >> > > I'll > >> > > do it. > >> >=20 > >> > I would like to get it right and match actual hardware. My proposal = is > >> > based on my understanding from the diagrams in the user manual. > >>=20 > >> So for now, your explanation is the most reasonable. Should we go ahead > >> and > >> implement your idea? > >>=20 > >> Please note that H6 has TCON-TOP too, but it has only one LCD TCON and > >> one > >> TV TCON instead of two of each kind. That means we will have hole in > >> indices (tcon_lcd0 is 1, tcon_tv0 is 3, which is aligned with R40) and > >> different TCON- TOP binding (no tcon_tv1 channel clock), but setup is > >> exactly the same. > >=20 > > I just noticed issue with this proposal. If we have following clock cha= in > > for HDMI, everythings is ok: > >=20 > > TCON-TV0 -> TCON-TOP-TV0 > >=20 > > TCON TV sets TCON-TOP-TV0 clock rate, which in turn sets TCON-TV0 clock > > and > > everything works. > >=20 > > However, when TVE will be configured, it would look like this: > >=20 > > TVE0 -> TCON-TOP-TV0 > >=20 > > TVE driver will set TVE0 clock to 216 MHz and TCON TV would set > > TCON-TOP-TV0 rate which in turn sets TVE0 clock to something like 13.5 > > MHz (or whatever is the right clock rate for PAL and NTSC). As you can > > see, same clock is set to two different rates by two different drivers. > >=20 > > It *might* still work, since encoders set clock rate after TCON (at lea= st > > that is my experience for HDMI pipeline), but that is still wrong. > >=20 > > To overcome above issue, I would stick to original proposal with > > additional > > clock specified in TCON TV DT node. That way TCON driver would always s= et > > clock rate to TCON-TV0 clock. If TVE0 is enabled, TCON wouldn't interfe= re > > with setting clock rate, because TCON-TV0 clock would be decoupled in > > TCON-TOP mux. > >=20 > > What do you think? >=20 > I think this is the wrong representation, and worse, you are trying to wo= rk > around software issues with it. >=20 > So to confirm some details, the TVE expects 216 MHz clock, and it expects > the TCON to run and output data at 216 MHz as well. Is that correct? Yes, from my understanding. 216 MHz is correct at least for PAL and NTSC, e= =2Eg.=20 TV mode. TVE on R40 is also capable of RGB mode (VGA connector). >=20 > Would any settings for the TCON differ between when HDMI or TVE is used? >=20 Apart of clock, no, other settings would be the same. > Does TVE and TCON run at 216 MHz regardless of resolution? I kind of doubt > it. It might be expecting 297 MHz for PC resolutions. Please check this table in BSP: https://github.com/BPI-SINOVOIP/BPI-M2U-bsp/blob/master/linux-sunxi/drivers/ video/sunxi/disp2/tv/drv_tv.c#L24 216 MHz is applicable for low resolution, interlaced modes. Modes like 1080= P,=20 1080I have expected standard timing. >=20 > I think these kinds of quirks should be handled in the software, instead = of > being papered over. Ok, that works for me too. I would just like to have such design that would= =20 later allow implementing TVE driver without much issues. BTW, H3 TV TCON which is connected to TVE doesn't have TCON-TV channel cloc= k=20 at all, since it is controlled with TVE clock (same case as it would be her= e,=20 if TCON TOP mux is switched to TVE clock source). Maybe quirk can be added that it doesn't set clock rate at all if it is=20 connected to TVE? Best regards, Jernej