linux-kernel - Re: [PATCH v3 08/12] arm64: dts: exynos: gs101: remove reg-io-width from serial

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Message-ID: <CAPLW+4mUMx9RvFiS0L2U+_Fd_PzcHhmNbyR4cmUrYF3BVgb=Cw@mail.gmail.com>
Date: Tue, 16 Jan 2024 11:57:54 -0600
From: Sam Protsenko <semen.protsenko@...aro.org>
To: Tudor Ambarus <tudor.ambarus@...aro.org>
Cc: peter.griffin@...aro.org, krzysztof.kozlowski+dt@...aro.org, 
	gregkh@...uxfoundation.org, mturquette@...libre.com, sboyd@...nel.org, 
	robh+dt@...nel.org, conor+dt@...nel.org, andi.shyti@...nel.org, 
	alim.akhtar@...sung.com, jirislaby@...nel.org, s.nawrocki@...sung.com, 
	tomasz.figa@...il.com, cw00.choi@...sung.com, 
	linux-arm-kernel@...ts.infradead.org, linux-samsung-soc@...r.kernel.org, 
	linux-clk@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org, 
	linux-serial@...r.kernel.org, andre.draszik@...aro.org, 
	kernel-team@...roid.com, willmcvicker@...gle.com
Subject: Re: [PATCH v3 08/12] arm64: dts: exynos: gs101: remove reg-io-width
 from serial

On Tue, Jan 9, 2024 at 7:00 AM Tudor Ambarus <tudor.ambarus@...aro.org> wrote:
>
> Remove the reg-io-width property in order to comply with the bindings.
>
> The entire bus (PERIC) on which the GS101 serial resides only allows
> 32-bit register accesses. The reg-io-width dt property is disallowed
> for the "google,gs101-uart" compatible and instead the iotype is
> inferred from the compatible.
>
> Reviewed-by: Peter Griffin <peter.griffin@...aro.org>
> Signed-off-by: Tudor Ambarus <tudor.ambarus@...aro.org>
> ---

Reviewed-by: Sam Protsenko <semen.protsenko@...aro.org>

Just out of curiosity (I probably missed the relevant discussion
earlier): what is the actual reason for moving 'reg-io-width' to the
driver's code as 'iotype'? I mean, what is the actual problem that's
being solved by this -- is it to make the earlycon functional for
gs101? I'm asking because the bus width looks like a part of HW
description, which usually belongs to dts, from the design point of
view. Anyways, that's not a concern, just trying to understand the
decision.

> v3: collect Peter's R-b tag
> v2: new patch
>
>  arch/arm64/boot/dts/exynos/google/gs101.dtsi | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/arch/arm64/boot/dts/exynos/google/gs101.dtsi b/arch/arm64/boot/dts/exynos/google/gs101.dtsi
> index d838e3a7af6e..4e5f4c748906 100644
> --- a/arch/arm64/boot/dts/exynos/google/gs101.dtsi
> +++ b/arch/arm64/boot/dts/exynos/google/gs101.dtsi
> @@ -366,7 +366,6 @@ usi_uart: usi@...000c0 {
>                         serial_0: serial@...00000 {
>                                 compatible = "google,gs101-uart";
>                                 reg = <0x10a00000 0xc0>;
> -                               reg-io-width = <4>;
>                                 interrupts = <GIC_SPI 634
>                                               IRQ_TYPE_LEVEL_HIGH 0>;
>                                 clocks = <&dummy_clk 0>, <&dummy_clk 0>;
> --
> 2.43.0.472.g3155946c3a-goog
>
>