Re: [PATCH 1/2] arm64: dts: amlogic: t7: use the real UART pclk

[Ronald Claveau <linux-kernel-dev@aliel.fr>]

On 8/19/26 4:39 AM, Xianwei Zhao wrote:
> Hi Lucas,
> 
> On 2026/8/19 03:11, Lucas Tanure wrote:
>> uart_a lists the 24MHz crystal for all three of its clocks, because
>> the T7 clock controller driver did not exist when these boards were
>> added.
>>
>> That leaves the real UART bus clock without a user, so the kernel
>> turns it off when it disables unused clocks at the end of boot, and
>> the board hangs.
>>
>> Point uart_a at the real clocks, the way meson-s4.dtsi does, and drop
>> the placeholders from the two board files.
>>
>> Fixes: 4fef056588f5 ("arm64: dts: amlogic-t7-a311d2-khadas-vim4: add
>> initial device-tree")
>> Fixes: 6f048cc7a635 ("arm64: dts: add board AN400")
>> Signed-off-by: Lucas Tanure<tanure@linux.com>
>> Assisted-by: Claude:claude-fable-5
>> ---
>>   arch/arm64/boot/dts/amlogic/amlogic-t7-a311d2-an400.dts       | 2 --
>>   arch/arm64/boot/dts/amlogic/amlogic-t7-a311d2-khadas-vim4.dts | 2 --
>>   arch/arm64/boot/dts/amlogic/amlogic-t7.dtsi                   | 4 ++++
>>   3 files changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/arm64/boot/dts/amlogic/amlogic-t7-a311d2-an400.dts
>> b/arch/arm64/boot/dts/amlogic/amlogic-t7-a311d2-an400.dts
>> index cab2ee9ea0d3..dcbcd08a78b9 100644
>> --- a/arch/arm64/boot/dts/amlogic/amlogic-t7-a311d2-an400.dts
>> +++ b/arch/arm64/boot/dts/amlogic/amlogic-t7-a311d2-an400.dts
>> @@ -33,7 +33,5 @@ xtal: xtal-clk {
>>   };
>>
>>   &uart_a {
>> -       clocks = <&xtal>, <&xtal>,
>> <&xtal>;
>> -       clock-names = "xtal", "pclk", "baud";
>>          status = "okay";
>>   };
>> diff --git
>> a/arch/arm64/boot/dts/amlogic/amlogic-t7-a311d2-khadas-vim4.dts
>> b/arch/arm64/boot/dts/amlogic/amlogic-t7-a311d2-khadas-vim4.dts
>> index c41525a34b72..677069e58f30 100644
>> --- a/arch/arm64/boot/dts/amlogic/amlogic-t7-a311d2-khadas-vim4.dts
>> +++ b/arch/arm64/boot/dts/amlogic/amlogic-t7-a311d2-khadas-vim4.dts
>> @@ -266,6 +266,4 @@ &sd_emmc_c {
>>
>>   &uart_a {
>>          status = "okay";
>> -       clocks = <&xtal>, <&xtal>,
>> <&xtal>;
>> -       clock-names = "xtal", "pclk", "baud";
>>   };
>> diff --git a/arch/arm64/boot/dts/amlogic/amlogic-t7.dtsi
>> b/arch/arm64/boot/dts/amlogic/amlogic-t7.dtsi
>> index cc371fcd1896..7847582e77ed 100644
>> --- a/arch/arm64/boot/dts/amlogic/amlogic-t7.dtsi
>> +++ b/arch/arm64/boot/dts/amlogic/amlogic-t7.dtsi
>> @@ -587,6 +587,10 @@ uart_a: serial@78000 {
>>                                  compatible = "amlogic,t7-uart",
>> "amlogic,meson-s4-uart";
>>                                  reg = <0x0 0x78000 0x0 0x18>;
>>                                  interrupts = <GIC_SPI 168
>> IRQ_TYPE_EDGE_RISING>;
>> +                               clocks = <&xtal>,
>> +                                        <&clkc_periphs
>> CLKID_SYS_UART_A>,
>> +                                        <&xtal>;
>> +                               clock-names = "xtal", "pclk", "baud";
>>                                  status = "disabled";
>>                          };
> 
> I agree with moving the UART clock configuration to the DTSI file.
> However, it seems a little odd to keep the XTAL clock definition in the
> DTS, as the alias may not be consistent across different boards, which
> could result in compilation errors. Could we move the XTAL clock
> definition to the DTSI as well, similar to other Amlogic SoCs?

It seems similar to changes in this series :

https://lore.kernel.org/all/20260420-add-bluetooth-t7-vim4-v4-0-9505df0e7016@aliel.fr/

What do you think ?

-- 
Best regards,
Ronald

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