drm/tidss: Fixes data edge sampling

[PATCH 3/4] arm64: dts: ti: k3-am62-main: Add tidss clk-ctrl property

Posted by Louis Chauvet 2 months, 1 week ago

For am62 processors, we need to use the newly created clk-ctrl property to
properly handle data edge sampling configuration. Add them in the main
device tree.

Fixes: 32a1795f57ee ("drm/tidss: New driver for TI Keystone platform Display SubSystem")
Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
---

Cc: stable@vger.kernel.org
---
 arch/arm64/boot/dts/ti/k3-am62-main.dtsi | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm64/boot/dts/ti/k3-am62-main.dtsi b/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
index 9e0b6eee9ac77d66869915b2d7bec3e2275c03ea..d3131e6da8e70fde035d3c44716f939e8167795a 100644
--- a/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
+++ b/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
@@ -76,6 +76,11 @@ audio_refclk1: clock-controller@82e4 {
 			assigned-clock-parents = <&k3_clks 157 18>;
 			#clock-cells = <0>;
 		};
+
+		dss_clk_ctrl: dss_clk_ctrl@8300 {
+			compatible = "ti,am625-dss-clk-ctrl", "syscon";
+			reg = <0x8300 0x4>;
+		};
 	};
 
 	dmss: bus@48000000 {
@@ -787,6 +792,7 @@ dss: dss@30200000 {
 			 <&k3_clks 186 2>;
 		clock-names = "fck", "vp1", "vp2";
 		interrupts = <GIC_SPI 84 IRQ_TYPE_LEVEL_HIGH>;
+		ti,clk-ctrl = <&dss_clk_ctrl>;
 		status = "disabled";
 
 		dss_ports: ports {

-- 
2.50.1

Re: [PATCH 3/4] arm64: dts: ti: k3-am62-main: Add tidss clk-ctrl property

Posted by Rob Herring 2 months ago

On Wed, Jul 30, 2025 at 07:02:46PM +0200, Louis Chauvet wrote:
> For am62 processors, we need to use the newly created clk-ctrl property to
> properly handle data edge sampling configuration. Add them in the main
> device tree.
> 
> Fixes: 32a1795f57ee ("drm/tidss: New driver for TI Keystone platform Display SubSystem")
> Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
> ---
> 
> Cc: stable@vger.kernel.org
> ---
>  arch/arm64/boot/dts/ti/k3-am62-main.dtsi | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/ti/k3-am62-main.dtsi b/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
> index 9e0b6eee9ac77d66869915b2d7bec3e2275c03ea..d3131e6da8e70fde035d3c44716f939e8167795a 100644
> --- a/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
> +++ b/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
> @@ -76,6 +76,11 @@ audio_refclk1: clock-controller@82e4 {
>  			assigned-clock-parents = <&k3_clks 157 18>;
>  			#clock-cells = <0>;
>  		};
> +
> +		dss_clk_ctrl: dss_clk_ctrl@8300 {
> +			compatible = "ti,am625-dss-clk-ctrl", "syscon";
> +			reg = <0x8300 0x4>;

H/w blocks are rarely only 4 bytes of registers... Does this belong to 
some larger block. The problem with bindings defining single registers 
like this is they don't get defined until needed and you have a constant 
stream of DT updates.

> +		};
>  	};
>  
>  	dmss: bus@48000000 {
> @@ -787,6 +792,7 @@ dss: dss@30200000 {
>  			 <&k3_clks 186 2>;
>  		clock-names = "fck", "vp1", "vp2";
>  		interrupts = <GIC_SPI 84 IRQ_TYPE_LEVEL_HIGH>;
> +		ti,clk-ctrl = <&dss_clk_ctrl>;
>  		status = "disabled";
>  
>  		dss_ports: ports {
> 
> -- 
> 2.50.1
>

Re: [PATCH 3/4] arm64: dts: ti: k3-am62-main: Add tidss clk-ctrl property

Posted by Louis Chauvet 2 months ago


Le 31/07/2025 à 02:17, Rob Herring a écrit :
> On Wed, Jul 30, 2025 at 07:02:46PM +0200, Louis Chauvet wrote:
>> For am62 processors, we need to use the newly created clk-ctrl property to
>> properly handle data edge sampling configuration. Add them in the main
>> device tree.
>>
>> Fixes: 32a1795f57ee ("drm/tidss: New driver for TI Keystone platform Display SubSystem")
>> Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
>> ---
>>
>> Cc: stable@vger.kernel.org
>> ---
>>   arch/arm64/boot/dts/ti/k3-am62-main.dtsi | 6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> diff --git a/arch/arm64/boot/dts/ti/k3-am62-main.dtsi b/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
>> index 9e0b6eee9ac77d66869915b2d7bec3e2275c03ea..d3131e6da8e70fde035d3c44716f939e8167795a 100644
>> --- a/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
>> +++ b/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
>> @@ -76,6 +76,11 @@ audio_refclk1: clock-controller@82e4 {
>>   			assigned-clock-parents = <&k3_clks 157 18>;
>>   			#clock-cells = <0>;
>>   		};
>> +
>> +		dss_clk_ctrl: dss_clk_ctrl@8300 {
>> +			compatible = "ti,am625-dss-clk-ctrl", "syscon";
>> +			reg = <0x8300 0x4>;
> 
> H/w blocks are rarely only 4 bytes of registers... Does this belong to
> some larger block. The problem with bindings defining single registers
> like this is they don't get defined until needed and you have a constant
> stream of DT updates.

In this case, I don't think there is a "larger block". This register 
exists only because TI had issues in the display controller [1].

Here is the extract of MMR registers ([2], page 4311):

[...]
A2E4h AUDIO_REFCLK1_CTRL_PROXY <unrelated>
A300h DPI0_CLK_CTRL_PROXY <this register, 32 bits>
<nothing between 0xA304 and 0xA319>
A320h DSS_DISPC0_CLKSEL1_PROXY <an other dss clock stuff, 32 bits>
A330h MCASP0_CLKSEL_PROXY <unrelated>
[...]

I agree that DSS_DISPC_CLKSEL_PROXY is also related to DSS clock stuff, 
so may be included in the same block, but there is also a big hole in 
between. What do you think is better?

[1]:https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1228207/am62a7-rgb-display-flickering-and-pixel-issue/4687209#4687209
[2]:https://www.ti.com/lit/ug/spruiv7b/spruiv7b.pdf#page=4311

>> +		};
>>   	};
>>   
>>   	dmss: bus@48000000 {
>> @@ -787,6 +792,7 @@ dss: dss@30200000 {
>>   			 <&k3_clks 186 2>;
>>   		clock-names = "fck", "vp1", "vp2";
>>   		interrupts = <GIC_SPI 84 IRQ_TYPE_LEVEL_HIGH>;
>> +		ti,clk-ctrl = <&dss_clk_ctrl>;
>>   		status = "disabled";
>>   
>>   		dss_ports: ports {
>>
>> -- 
>> 2.50.1
>>

-- 
Louis Chauvet, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

Re: [PATCH 3/4] arm64: dts: ti: k3-am62-main: Add tidss clk-ctrl property

Posted by Krzysztof Kozlowski 2 months ago

On Thu, Jul 31, 2025 at 11:50:16AM +0200, Louis Chauvet wrote:
> 
> 
> Le 31/07/2025 à 02:17, Rob Herring a écrit :
> > On Wed, Jul 30, 2025 at 07:02:46PM +0200, Louis Chauvet wrote:
> > > For am62 processors, we need to use the newly created clk-ctrl property to
> > > properly handle data edge sampling configuration. Add them in the main
> > > device tree.
> > > 
> > > Fixes: 32a1795f57ee ("drm/tidss: New driver for TI Keystone platform Display SubSystem")
> > > Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
> > > ---
> > > 
> > > Cc: stable@vger.kernel.org
> > > ---
> > >   arch/arm64/boot/dts/ti/k3-am62-main.dtsi | 6 ++++++
> > >   1 file changed, 6 insertions(+)
> > > 
> > > diff --git a/arch/arm64/boot/dts/ti/k3-am62-main.dtsi b/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
> > > index 9e0b6eee9ac77d66869915b2d7bec3e2275c03ea..d3131e6da8e70fde035d3c44716f939e8167795a 100644
> > > --- a/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
> > > +++ b/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
> > > @@ -76,6 +76,11 @@ audio_refclk1: clock-controller@82e4 {
> > >   			assigned-clock-parents = <&k3_clks 157 18>;
> > >   			#clock-cells = <0>;
> > >   		};
> > > +
> > > +		dss_clk_ctrl: dss_clk_ctrl@8300 {
> > > +			compatible = "ti,am625-dss-clk-ctrl", "syscon";
> > > +			reg = <0x8300 0x4>;
> > 
> > H/w blocks are rarely only 4 bytes of registers... Does this belong to
> > some larger block. The problem with bindings defining single registers
> > like this is they don't get defined until needed and you have a constant
> > stream of DT updates.
> 
> In this case, I don't think there is a "larger block". This register exists
> only because TI had issues in the display controller [1].
> 
> Here is the extract of MMR registers ([2], page 4311):
> 
> [...]
> A2E4h AUDIO_REFCLK1_CTRL_PROXY <unrelated>

Here is clk ctrl proxy...

> A300h DPI0_CLK_CTRL_PROXY <this register, 32 bits>

and here as well, so pretty related. This looks also close to regular
syscon and we do not define individual syscon registers as device nodes.

Best regards,
Krzysztof

Re: [PATCH 3/4] arm64: dts: ti: k3-am62-main: Add tidss clk-ctrl property

Posted by Louis Chauvet 1 month, 3 weeks ago


Le 05/08/2025 à 08:44, Krzysztof Kozlowski a écrit :
> On Thu, Jul 31, 2025 at 11:50:16AM +0200, Louis Chauvet wrote:
>>
>>
>> Le 31/07/2025 à 02:17, Rob Herring a écrit :
>>> On Wed, Jul 30, 2025 at 07:02:46PM +0200, Louis Chauvet wrote:
>>>> For am62 processors, we need to use the newly created clk-ctrl property to
>>>> properly handle data edge sampling configuration. Add them in the main
>>>> device tree.
>>>>
>>>> Fixes: 32a1795f57ee ("drm/tidss: New driver for TI Keystone platform Display SubSystem")
>>>> Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
>>>> ---
>>>>
>>>> Cc: stable@vger.kernel.org
>>>> ---
>>>>    arch/arm64/boot/dts/ti/k3-am62-main.dtsi | 6 ++++++
>>>>    1 file changed, 6 insertions(+)
>>>>
>>>> diff --git a/arch/arm64/boot/dts/ti/k3-am62-main.dtsi b/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
>>>> index 9e0b6eee9ac77d66869915b2d7bec3e2275c03ea..d3131e6da8e70fde035d3c44716f939e8167795a 100644
>>>> --- a/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
>>>> +++ b/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
>>>> @@ -76,6 +76,11 @@ audio_refclk1: clock-controller@82e4 {
>>>>    			assigned-clock-parents = <&k3_clks 157 18>;
>>>>    			#clock-cells = <0>;
>>>>    		};
>>>> +
>>>> +		dss_clk_ctrl: dss_clk_ctrl@8300 {
>>>> +			compatible = "ti,am625-dss-clk-ctrl", "syscon";
>>>> +			reg = <0x8300 0x4>;
>>>
>>> H/w blocks are rarely only 4 bytes of registers... Does this belong to
>>> some larger block. The problem with bindings defining single registers
>>> like this is they don't get defined until needed and you have a constant
>>> stream of DT updates.
>>
>> In this case, I don't think there is a "larger block". This register exists
>> only because TI had issues in the display controller [1].
>>
>> Here is the extract of MMR registers ([2], page 4311):
>>
>> [...]
>> A2E4h AUDIO_REFCLK1_CTRL_PROXY <unrelated>
> 
> Here is clk ctrl proxy...

(Note: I linked and copied the wrong page in my previous mail, the page 
is 4309 and register addresses are 0x82e4 (audio_refclk1_ctrl), 0x8300 
(dpi0_clk_ctrl) and 0x8320 (dss_dispc_clksel1), but the issue remain the 
same)

The AUDIO_REFCLK1_CTRL is already defined in the simple-bus node, but 
with a size of 0x4 [1] and as a clock controller.

What is the correct solution in this case? Should I create a big syscon 
that overlap with audio_refclk0/1 range?

[1]:https://elixir.bootlin.com/linux/v6.16/source/arch/arm64/boot/dts/ti/k3-am62-main.dtsi#L73

>> A300h DPI0_CLK_CTRL_PROXY <this register, 32 bits>
> 
> and here as well, so pretty related. This looks also close to regular
> syscon and we do not define individual syscon registers as device nodes.

I agree this one can be included in the syscon device. Clock related 
registers starts at 0x8000 and ends at 0x8504, should I cover the whole 
range in the syscon?

I quickly looked at the other register, here is the repartition:

- 0x8000 - "normal" clock (divider + source selection)
- 0x8040 to 0x8298 - clock source selection
- 0x82e0 to 0x82e4 - clock control for audio (already implemented as 
clock driver)
- 0x8300 - the clock quirk (it seems that this is the only quirk 
register here)
- 0x8320 to 0x8500 - clock source selection

Thanks,
Louis Chauvet

> Best regards,
> Krzysztof
> 

-- 
Louis Chauvet, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com