Re: [PATCH 21/27] arm64: dts: rockchip: rk356x: Add HDMI nodes

[Robin Murphy <robin.murphy@arm.com>]

On 2022-01-26 18:44, Peter Geis wrote:
> On Wed, Jan 26, 2022 at 12:56 PM Robin Murphy <robin.murphy@arm.com> wrote:
>>
>> On 2022-01-26 16:04, Peter Geis wrote:
>>> On Wed, Jan 26, 2022 at 9:58 AM Sascha Hauer <s.hauer@pengutronix.de> wrote:
>>>>
>>>> Add support for the HDMI port found on RK3568.
>>>>
>>>> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
>>>> ---
>>>>    arch/arm64/boot/dts/rockchip/rk356x.dtsi | 37 +++++++++++++++++++++++-
>>>>    1 file changed, 36 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/arch/arm64/boot/dts/rockchip/rk356x.dtsi b/arch/arm64/boot/dts/rockchip/rk356x.dtsi
>>>> index 4008bd666d01..e38fb223e9b8 100644
>>>> --- a/arch/arm64/boot/dts/rockchip/rk356x.dtsi
>>>> +++ b/arch/arm64/boot/dts/rockchip/rk356x.dtsi
>>>> @@ -10,7 +10,6 @@
>>>>    #include <dt-bindings/pinctrl/rockchip.h>
>>>>    #include <dt-bindings/power/rk3568-power.h>
>>>>    #include <dt-bindings/soc/rockchip,boot-mode.h>
>>>> -#include <dt-bindings/soc/rockchip,vop2.h>
>>>>    #include <dt-bindings/thermal/thermal.h>
>>>>
>>>>    / {
>>>> @@ -502,6 +501,42 @@ vop_mmu: iommu@fe043e00 {
>>>>                   status = "disabled";
>>>>           };
>>>>
>>>> +       hdmi: hdmi@fe0a0000 {
>>>> +               compatible = "rockchip,rk3568-dw-hdmi";
>>>> +               reg = <0x0 0xfe0a0000 0x0 0x20000>;
>>>> +               interrupts = <GIC_SPI 45 IRQ_TYPE_LEVEL_HIGH>;
>>>> +               clocks = <&cru PCLK_HDMI_HOST>,
>>>> +                        <&cru CLK_HDMI_SFR>,
>>>> +                        <&cru CLK_HDMI_CEC>,
>>>> +                        <&pmucru CLK_HDMI_REF>,
>>>> +                        <&cru HCLK_VOP>;
>>>> +               clock-names = "iahb", "isfr", "cec", "ref", "hclk";
>>>> +               pinctrl-names = "default";
>>>> +               pinctrl-0 = <&hdmitx_scl &hdmitx_sda &hdmitxm0_cec>;
>>>
>>> I looked into CEC support here, and it seems that it does work with one change.
>>> Please add the two following lines to your patch:
>>> assigned-clocks = <&cru CLK_HDMI_CEC>;
>>> assigned-clock-rates = <32768>;
>>>
>>> The issue is the clk_rtc32k_frac clock that feeds clk_rtc_32k which
>>> feeds clk_hdmi_cec is 24mhz at boot, which is too high for CEC to
>>> function.
>>
>> Wouldn't it make far more sense to just stick a suitable clk_set_rate()
>> call in the driver? AFAICS it's already explicitly aware of the CEC clock.
> 
> This is handled purely in the
> drivers/gpu/drm/bridge/synopsys/dw-hdmi.c driver, so I'm hesitant to
> touch it there as it would affect all users, not just Rockchip.

I'd have a strong hunch that it's a standard thing for the DesignWare IP 
and not affected by platform integration. I don't have the magical 
Synopsys databook, but between the trusty old i.MX6 manual and most of 
the other in-tree DTs getting their dw-hdmi "cec" clock from 
suspiciously-obviously-named sources, I'd be somewhat surprised if it 
was ever anything other than 32KHz.

Robin.

> Could someone familiar with the dw-hdmi IP weigh in on the minimum and
> maximum clock rate the CEC block can handle?
> 
>>
>> Robin.
>>
>>>> +               power-domains = <&power RK3568_PD_VO>;
>>>> +               reg-io-width = <4>;
>>>> +               rockchip,grf = <&grf>;
>>>> +               #sound-dai-cells = <0>;
>>>> +               status = "disabled";
>>>> +
>>>> +               ports {
>>>> +                       #address-cells = <1>;
>>>> +                       #size-cells = <0>;
>>>> +
>>>> +                       hdmi_in: port@0 {
>>>> +                               reg = <0>;
>>>> +                               #address-cells = <1>;
>>>> +                               #size-cells = <0>;
>>>> +                       };
>>>> +
>>>> +                       hdmi_out: port@1 {
>>>> +                               reg = <1>;
>>>> +                               #address-cells = <1>;
>>>> +                               #size-cells = <0>;
>>>> +                       };
>>>> +               };
>>>> +       };
>>>> +
>>>>           qos_gpu: qos@fe128000 {
>>>>                   compatible = "rockchip,rk3568-qos", "syscon";
>>>>                   reg = <0x0 0xfe128000 0x0 0x20>;
>>>> --
>>>> 2.30.2
>>>>
>>>
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