linux-kernel - Re: [PATCH v3 11/12] arm64: dts: exynos: gs101: define USI8 with I2C configuration

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Message-ID: <c72ca8b2-55a6-4ec7-8013-0a563d6dcdfe@linaro.org>
Date: Wed, 17 Jan 2024 15:08:27 +0000
From: Tudor Ambarus <tudor.ambarus@...aro.org>
To: Sam Protsenko <semen.protsenko@...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 11/12] arm64: dts: exynos: gs101: define USI8 with I2C
 configuration



On 1/16/24 18:03, Sam Protsenko wrote:
>> USI8 CONFIG register comes with a 0x0 reset value, meaning that USI8
>> doesn't have a default protocol (I2C, SPI, UART) at reset. Thus the
>> selection of the protocol is intentionally left for the board dts file.
>>
>> Signed-off-by: Tudor Ambarus <tudor.ambarus@...aro.org>
>> ---
>> v3: reorder usi8 clock order (thanks Andre'!). Did not make any
>> difference at testing as the usi driver treats the clocks in bulk.
>> v2:
>> - identify and use gate clocks instead of dividers
>> - move cells and pinctrl properties from dts to dtsi
>> - move IRQ type constant on the previous line
>>
>>  arch/arm64/boot/dts/exynos/google/gs101.dtsi | 29 ++++++++++++++++++++
>>  1 file changed, 29 insertions(+)
>>
>> diff --git a/arch/arm64/boot/dts/exynos/google/gs101.dtsi b/arch/arm64/boot/dts/exynos/google/gs101.dtsi
>> index 6aa25cc4676e..f14a24628d04 100644
>> --- a/arch/arm64/boot/dts/exynos/google/gs101.dtsi
>> +++ b/arch/arm64/boot/dts/exynos/google/gs101.dtsi
>> @@ -352,6 +352,35 @@ pinctrl_peric0: pinctrl@...40000 {
>>                         interrupts = <GIC_SPI 625 IRQ_TYPE_LEVEL_HIGH 0>;
>>                 };
>>
>> +               usi8: usi@...700c0 {
>> +                       compatible = "google,gs101-usi",
>> +                                    "samsung,exynos850-usi";
>> +                       reg = <0x109700c0 0x20>;
>> +                       ranges;
>> +                       #address-cells = <1>;
>> +                       #size-cells = <1>;
>> +                       clocks = <&cmu_peric0 CLK_GOUT_PERIC0_CLK_PERIC0_USI8_USI_CLK>,
>> +                                <&cmu_peric0 CLK_GOUT_PERIC0_PERIC0_TOP0_IPCLK_7>;
>> +                       clock-names = "pclk", "ipclk";
>> +                       samsung,sysreg = <&sysreg_peric0 0x101c>;
> I'd also add samsung,mode for the "default" USI mode here, just to
> avoid providing it later in the board's dts. But that's a matter of
> taste I guess.
> 

USI8 CONFIG register comes with a 0x0 reset value, meaning that USI8
doesn't have a default protocol (I2C, SPI, UART) at reset. Thus the
selection of the protocol is intentionally left for the board dts file.

I wanted to emphasize that USI8 doesn't have any HW defaults and its
mode must be chosen by each particular board.

I mentioned the same in the commit message, please tell if you feel it
needs updating.

Cheers,
ta