Re: [RFC v2 6/8] MIPS: DTS: jz4780: account for Synopsys HDMI driver and LCD controller

[Paul Cercueil]

Hi Nikolaus,


Le mer., mars 11, 2020 at 13:43, H. Nikolaus Schaller 
<hns@xxxxxxxxxxxxx> a écrit :
> Hi Paul,
>
> >  Am 02.03.2020 um 20:27 schrieb Paul Cercueil <paul@xxxxxxxxxxxxxxx>:
> >
> >  Hi Nikolaus,
> >
> >
> >  Le ven., févr. 28, 2020 at 19:19, H. Nikolaus Schaller 
> > <hns@xxxxxxxxxxxxx> a écrit :
> > >  From: Paul Boddie <paul@xxxxxxxxxxxxx>
> > >  A specialisation of the generic Synopsys HDMI driver is employed 
> > > for JZ4780
> > >  HDMI support. This requires a new driver, plus device tree and 
> > > configuration
> > >  modifications.
> > >  Signed-off-by: Paul Boddie <paul@xxxxxxxxxxxxx>
> > >  Signed-off-by: H. Nikolaus Schaller <hns@xxxxxxxxxxxxx>
> > >  ---
> > >  arch/mips/boot/dts/ingenic/jz4780.dtsi | 32 
> > > ++++++++++++++++++++++++++
> > >  1 file changed, 32 insertions(+)
> > >  diff --git a/arch/mips/boot/dts/ingenic/jz4780.dtsi 
> > > b/arch/mips/boot/dts/ingenic/jz4780.dtsi
> > >  index f928329b034b..391d4e1efd35 100644
> > >  --- a/arch/mips/boot/dts/ingenic/jz4780.dtsi
> > >  +++ b/arch/mips/boot/dts/ingenic/jz4780.dtsi
> > >  @@ -433,4 +433,36 @@
> > >  		status = "disabled";
> > >  	};
> > >  +
> > >  +	hdmi: hdmi@10180000 {
> > >  +		compatible = "ingenic,jz4780-dw-hdmi";
> > >  +		reg = <0x10180000 0x8000>;
> > >  +		reg-io-width = <4>;
> > >  +
> > >  +		clocks = <&cgu JZ4780_CLK_HDMI>, <&cgu JZ4780_CLK_AHB0>;
> > >  +		clock-names = "isfr" , "iahb";
> > >  +
> > >  +		assigned-clocks = <&cgu JZ4780_CLK_HDMI>;
> > >  +		assigned-clock-rates = <27000000>;
> >
> >  I *think* this should go to the board file.
> >
> > >  +
> > >  +		interrupt-parent = <&intc>;
> > >  +		interrupts = <3>;
> > >  +
> > >  +		/* ddc-i2c-bus = <&i2c4>; */
> > >  +
> > >  +		status = "disabled";
> > >  +	};
> > >  +
> > >  +	lcd: lcd@13050000 {
> >
> >  The node name should be 'lcd-controller'.
> >
> > >  +		compatible = "ingenic,jz4740-lcd";
> >
> >  The JZ4780's LCD controller is much newer than the JZ4740 one, so 
> > even if it works with the "ingenic,jz4740-lcd" compatible string, 
> > you want it as a fallback.
> >  So this should be: compatible = "ingenic,jz4780-lcd", 
> > "ingenic,jz4740-lcd".
> >
> >  That means the YAML should be updated too.
>
> I have started to look into jz4780 HDMI setup again.
>
> Well, there is no driver compatible to "ingenic,jz4780-lcd" so far
> and it is questionalbe if we need a different one.
>
> I think we should rather make the driver also compatible
> than adding a fallback to ingenic,jz4740-lcdto the DTS.
>
> The reason why this is better even if both LCDC are almost
> compatible is that the jz4780 allows for much bigger displays
> and therefore should have its own jz_soc_info with 4k x 2k
> as maximum.

Sure, feel free to extend the driver.

> Next I tried to find out if the LCDC are really compatible.
>
> Well the jz4780 has two lcdc instances but they are separated
> by the reg addr. Next, there are unique features (like picture in
> picture with alpha blending) but those are probably disabled
> if not programmed from reset state. This may become a reason
> to separate or augment the driver for the jz4780 but at the
> moment we can ignore that.

Two LCDC instances -> two lcd-controller@... nodes. It's that simple.

The other features you listed are outside the LCDC, so outside the 
scope of this driver.

> There are also subtly different bit definitions and register
> widths (e.g. 24 bit in addition to 16/18 bit modes or more bits
> for the sync position) but it looks as if the ingenic_drm
> driver already handles this.
>
> Then I tried to read back the registers. Strangely they
> are all 0x00000000. So there is no programming of the
> lcd-controller in our DT setup with HDMI at all!

How did you read them?
Do it from the regmap: should be "cat 
/sys/kernel/debug/regmap/13050000.lcd-controller/registers" (not sure 
about the path)

> I also checked that ingenic_drm_probe() is called and
> returns successfully 0. It also reports that a /dev/fb
> has been created:
>
> [    7.908830] ingenic-drm 13050000.lcd-controller: fb0: 
> ingenic-drmdrmf frame buffer device
>
> But for example ingenic_drm_encoder_atomic_mode_set() is
> never called which should write some registers of the LCDC.
>
> I only did see some calls to ingenic_drm_encoder_atomic_check().
>
> This of course explains why we have no HDMI signals despite
> proper HPD and a /dev/fb0. Because the LCDC is not being
> programmed.

It won't be called until the HDMI driver says that the cable is 
plugged, and there's a client application (e.g. fbdev emulation) 
running. So the problem is most likely within the HDMI driver.

Cheers,
-Paul

> Any ideas / hints how to check or improve?
>
> BR and thanks,
> Nikolaus