[PATCH] arm64: dts: renesas: r8a779g0: Fix HSCIF0 "brg_int" clock

[PATCH] arm64: dts: renesas: r8a779g0: Fix HSCIF0 "brg_int" clock

[Geert Uytterhoeven]

As serial communication requires a clock signal, the High Speed Serial
Communication Interfaces with FIFO (HSCIF) are clocked by a clock that
is not affected by Spread Spectrum or Fractional Multiplication.

Hence change the clock input for the HSCIF0 Baud Rate Generator internal
clock from the S0D3_PER clock to the SASYNCPERD1 clock (which has the
same clock rate), cfr. R-Car V4H Hardware User's Manual rev. 0.54.

Fixes: 987da486d84a5643 ("arm64: dts: renesas: Add Renesas R8A779G0 SoC support")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
For full proper operation, this depends on "[PATCH 1/5] clk: renesas:
r8a779g0: Add SASYNCPER clocks"[1].
However, as the "brg_int" clock is optional, the serial driver will keep
on functioning without it, and just resort to a less optimal clock
input/divider combination, which is still good enough for the serial
console.

[1] https://lore.kernel.org/r/d0f35c35e1f96c5a649ab477e7ba5d8025957cd0.1665147497.git.geert+renesas@glider.be
---
 arch/arm64/boot/dts/renesas/r8a779g0.dtsi | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/boot/dts/renesas/r8a779g0.dtsi b/arch/arm64/boot/dts/renesas/r8a779g0.dtsi
index edabd1519ccc979d..c941054f4980667b 100644
--- a/arch/arm64/boot/dts/renesas/r8a779g0.dtsi
+++ b/arch/arm64/boot/dts/renesas/r8a779g0.dtsi
@@ -360,7 +360,7 @@ hscif0: serial@e6540000 {
 			reg = <0 0xe6540000 0 96>;
 			interrupts = <GIC_SPI 246 IRQ_TYPE_LEVEL_HIGH>;
 			clocks = <&cpg CPG_MOD 514>,
-				 <&cpg CPG_CORE R8A779G0_CLK_S0D3_PER>,
+				 <&cpg CPG_CORE R8A779G0_CLK_SASYNCPERD1>,
 				 <&scif_clk>;
 			clock-names = "fck", "brg_int", "scif_clk";
 			dmas = <&dmac0 0x31>, <&dmac0 0x30>,
-- 
2.25.1


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Re: [PATCH] arm64: dts: renesas: r8a779g0: Fix HSCIF0 "brg_int" clock

[Wolfram Sang]

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On Fri, Oct 07, 2022 at 05:20:03PM +0200, Geert Uytterhoeven wrote:
> As serial communication requires a clock signal, the High Speed Serial
> Communication Interfaces with FIFO (HSCIF) are clocked by a clock that
> is not affected by Spread Spectrum or Fractional Multiplication.
> 
> Hence change the clock input for the HSCIF0 Baud Rate Generator internal
> clock from the S0D3_PER clock to the SASYNCPERD1 clock (which has the
> same clock rate), cfr. R-Car V4H Hardware User's Manual rev. 0.54.
> 
> Fixes: 987da486d84a5643 ("arm64: dts: renesas: Add Renesas R8A779G0 SoC support")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>

Do we need to wait for the clarification about the docs mentioned in
another thread?


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Re: [PATCH] arm64: dts: renesas: r8a779g0: Fix HSCIF0 "brg_int" clock

[Geert Uytterhoeven]

Hi Wolfram,

On Mon, Oct 10, 2022 at 9:56 AM Wolfram Sang <wsa@kernel.org> wrote:
> On Fri, Oct 07, 2022 at 05:20:03PM +0200, Geert Uytterhoeven wrote:
> > As serial communication requires a clock signal, the High Speed Serial
> > Communication Interfaces with FIFO (HSCIF) are clocked by a clock that
> > is not affected by Spread Spectrum or Fractional Multiplication.
> >
> > Hence change the clock input for the HSCIF0 Baud Rate Generator internal
> > clock from the S0D3_PER clock to the SASYNCPERD1 clock (which has the
> > same clock rate), cfr. R-Car V4H Hardware User's Manual rev. 0.54.
> >
> > Fixes: 987da486d84a5643 ("arm64: dts: renesas: Add Renesas R8A779G0 SoC support")
> > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
>
> Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>

Thanks!

> Do we need to wait for the clarification about the docs mentioned in
> another thread?

This one matches the docs ;-)
It's the module clock's parent in the clock driver which doesn't seem to
match actual hardware.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

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