linux-kernel - RE: [PATCH v3 2/2] i2c: exynos5: add support for ExynosAutov9 SoC

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Message-ID: <001401d7da86$f7ebd660$e7c38320$@samsung.com>
Date:   Tue, 16 Nov 2021 10:12:04 +0900
From:   "Chanho Park" <chanho61.park@...sung.com>
To:     "'Sam Protsenko'" <semen.protsenko@...aro.org>,
        "'Jaewon Kim'" <jaewon02.kim@...sung.com>
Cc:     "'Krzysztof Kozlowski'" <krzysztof.kozlowski@...onical.com>,
        "'Wolfram Sang'" <wsa@...nel.org>,
        "'Rob Herring'" <robh+dt@...nel.org>,
        <linux-samsung-soc@...r.kernel.org>, <linux-i2c@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: RE: [PATCH v3 2/2] i2c: exynos5: add support for ExynosAutov9 SoC

> With this patch the Exynos850 HSI2C becomes functional. The only nit-pick
> from my side (just a food for thought): do we want to configure USI
> related config inside of particular drivers (SPI, I2C, UART)? Or it would
> be better design to implement some platform driver for that, so we can
> choose USI configuration (SPI/I2C/UART) in device tree? I think this
> series is good to be merged as is, but we should probably consider all
> upsides and downsides of each option, for the future work.

I'm also considering how to support this USI configuration gracefully.
Current version of USI is v2 which means there is a v1 version as well. It might be a non-upstream SoC so we don't need to consider it so far.
But, there is a possibility that the USI hw version can be bumped for future SoCs.

As you probably know, earlier version of the product kernel has a USI SoC driver[1] and it was designed to be configured the USI settings by device tree.

Option1) Make a USI driver under soc/samsung/ like [1].
Option2) Use more generic driver such as "reset driver"? This might be required to extend the reset core driver.
Option3) Each USI driver(uart/i2c/spi) has its own USI configurations respectively and expose some configurations which can be variable as device tree.

[1]: https://github.com/ianmacd/d2s/blob/master/drivers/soc/samsung/usi_v2.c

Best Regards,
Chanho Park