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SubjectRe: [PATCH 3/3] ARM64: dts: meson: fix clock source of the pclk for UART_AO
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On 03/27/2018 05:20 PM, Jerome Brunet wrote:
> On Mon, 2018-03-26 at 16:18 +0800, Yixun Lan wrote:
>> From the hardware perspective, the clk81 is the parent of
>> the UART_AO clocks. So it make more sense to mark
>> the CLKID_AO_UART1/2 as the pclk.
>>
>> Previous we had flag=CLK_IGNORE_UNUSED in AO clock driver.
>> This will make kernel leave clock as it is while bootloader
>> set the clock on.
>>
>
> Hi Yixun,
>
> I'm not sure I understand your description correctly so I'll phrase. Please tell
> me if I misunderstood something
>
> The actual pclk of the AO uarts is the corresponding clkc_ao uart gate, not the
> main clock controller clk81. This was not problem so far, because the uart_gate
> had the CLK_IGNORE_UNUSED flag, which kept the gate open.
>
Yes, exactly

> In another patch, you removed this flag, so you need to give the correct clock
> in DT to make things work again ? right ?
>
Yes, right.


> If I got it correctly, please rephrase the description a bit.
> Also you need to be careful in which order patches get merged.
>
> 1. You need the clkc_ao in place, exporting CLKID_AO_UARTx with
> CLK_IGNORE_UNUSED.
>
> 2. This patch can be merged (still with CLK_IGNORE_UNUSED)
>
> 3. Once the DT patch have reached mainline, you should a patch to remove to
> CLK_IGNORE_UNUSED flag
>
> This way, we avoid breaking bisect, with revision where CLKID_AO_UARTx would get
> disabled by the CCF clk_disable_unused() mechanism while the UART driver does
> not claim the appropriate clock.
>
I wasn't sure about what's the best approach
I just gave a warning about that patch 2 (removing CLK_IGNORE_UNUSED)
and patch 3 (fix the DTS) should be merged together

and your suggestion sounds good, I will adjust

>
>> Signed-off-by: Yixun Lan <yixun.lan@amlogic.com>
>> ---
>> arch/arm64/boot/dts/amlogic/meson-axg.dtsi | 4 ++--
>> arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi | 4 ++--
>> arch/arm64/boot/dts/amlogic/meson-gxl.dtsi | 4 ++--
>> 3 files changed, 6 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/arm64/boot/dts/amlogic/meson-axg.dtsi b/arch/arm64/boot/dts/amlogic/meson-axg.dtsi
>> index 48584d5a329b..e538e2448bb5 100644
>> --- a/arch/arm64/boot/dts/amlogic/meson-axg.dtsi
>> +++ b/arch/arm64/boot/dts/amlogic/meson-axg.dtsi
>> @@ -533,7 +533,7 @@
>> compatible = "amlogic,meson-gx-uart", "amlogic,meson-ao-uart";
>> reg = <0x0 0x3000 0x0 0x18>;
>> interrupts = <GIC_SPI 193 IRQ_TYPE_EDGE_RISING>;
>> - clocks = <&xtal>, <&clkc CLKID_CLK81>, <&xtal>;
>> + clocks = <&xtal>, <&clkc_AO CLKID_AO_UART1>, <&xtal>;
>> clock-names = "xtal", "pclk", "baud";
>> status = "disabled";
>> };
>> @@ -542,7 +542,7 @@
>> compatible = "amlogic,meson-gx-uart", "amlogic,meson-ao-uart";
>> reg = <0x0 0x4000 0x0 0x18>;
>> interrupts = <GIC_SPI 197 IRQ_TYPE_EDGE_RISING>;
>> - clocks = <&xtal>, <&clkc CLKID_CLK81>, <&xtal>;
>> + clocks = <&xtal>, <&clkc_AO CLKID_AO_UART2>, <&xtal>;
>> clock-names = "xtal", "pclk", "baud";
>> status = "disabled";
>> };
>> diff --git a/arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi b/arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi
>> index 3290a4dc3522..a458ea50c2ef 100644
>> --- a/arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi
>> +++ b/arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi
>> @@ -783,12 +783,12 @@
>> };
>>
>> &uart_AO {
>> - clocks = <&xtal>, <&clkc CLKID_CLK81>, <&xtal>;
>> + clocks = <&xtal>, <&clkc_AO CLKID_AO_UART1>, <&xtal>;
>> clock-names = "xtal", "pclk", "baud";
>> };
>>
>> &uart_AO_B {
>> - clocks = <&xtal>, <&clkc CLKID_CLK81>, <&xtal>;
>> + clocks = <&xtal>, <&clkc_AO CLKID_AO_UART2>, <&xtal>;
>> clock-names = "xtal", "pclk", "baud";
>> };
>>
>> diff --git a/arch/arm64/boot/dts/amlogic/meson-gxl.dtsi b/arch/arm64/boot/dts/amlogic/meson-gxl.dtsi
>> index 4f355f17eed6..474f4f9630e4 100644
>> --- a/arch/arm64/boot/dts/amlogic/meson-gxl.dtsi
>> +++ b/arch/arm64/boot/dts/amlogic/meson-gxl.dtsi
>> @@ -733,12 +733,12 @@
>> };
>>
>> &uart_AO {
>> - clocks = <&xtal>, <&clkc CLKID_CLK81>, <&xtal>;
>> + clocks = <&xtal>, <&clkc_AO CLKID_AO_UART1>, <&xtal>;
>> clock-names = "xtal", "pclk", "baud";
>> };
>>
>> &uart_AO_B {
>> - clocks = <&xtal>, <&clkc CLKID_CLK81>, <&xtal>;
>> + clocks = <&xtal>, <&clkc_AO CLKID_AO_UART2>, <&xtal>;
>> clock-names = "xtal", "pclk", "baud";
>> };
>>
>
> .
>

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