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Sun, 23 Aug 2026 04:39:01 -0700 (PDT) Message-ID: <0969d872-faff-4b0f-81ad-972b7aa9bb7f@linux.com> Date: Sun, 23 Aug 2026 12:39:00 +0100 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] arm64: dts: amlogic: t7: use the real UART pclk To: Ronald Claveau , Xianwei Zhao Cc: linux-arm-kernel@lists.infradead.org, linux-amlogic@lists.infradead.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Neil Armstrong , Kevin Hilman , Rob Herring , Krzysztof Kozlowski , Conor Dooley References: <20260818191159.11523-1-tanure@linux.com> <20260818191159.11523-2-tanure@linux.com> <6673edea-6822-4368-9374-29f92195fcf5@aliel.fr> Content-Language: en-US From: Lucas Tanure In-Reply-To: <6673edea-6822-4368-9374-29f92195fcf5@aliel.fr> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 19/08/2026 08:25, Ronald Claveau wrote: > 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 >>> 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 = >> 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 ? > Thanks for pointing out that series, though I wasn't aware of it. And after reading I don't agree with it. The clocks are not redundant, they are there because we agreed sometime ago that xtal belongs to the board files. So I still vote for my change in v2, that I will send in a few minutes.