linux-kernel - Re: [PATCH v2 RESEND 3/5] tty: serial: samsung: Remove USI initialization

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Message-ID: <CAPLW+4mEw0x_rZ19h+rbz4qm=6OVgQvvbEJWL0wWQguMiWB7-g@mail.gmail.com>
Date:   Fri, 3 Dec 2021 18:22:24 +0200
From:   Sam Protsenko <semen.protsenko@...aro.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Chanho Park <chanho61.park@...sung.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Jaewon Kim <jaewon02.kim@...sung.com>,
        David Virag <virag.david003@...il.com>,
        Youngmin Nam <youngmin.nam@...sung.com>,
        devicetree <devicetree@...r.kernel.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Samsung SOC <linux-samsung-soc@...r.kernel.org>
Subject: Re: [PATCH v2 RESEND 3/5] tty: serial: samsung: Remove USI initialization

On Wed, 1 Dec 2021 at 12:54, Andy Shevchenko <andy.shevchenko@...il.com> wrote:
>
> On Wed, Dec 1, 2021 at 12:42 AM Sam Protsenko
> <semen.protsenko@...aro.org> wrote:
> >
> > USI control is now extracted to dedicated USI driver. Remove USI related
>
> the dedicated
>
> > code from serial driver to avoid conflicts and code duplication.
>
> Would it break run-time bisectability?
> If so, why is it not a problem?
>

It shouldn't. This patch is [3/5], and USI driver (which takes the
control over the USI registers) is [2/5]. As for Device Tree, the only
platform using "samsung,exynos850-uart" right now is Exynos Auto V9
SADK (serial node is declared in exynosautov9.dtsi). I don't have
Exynos Auto V9 datasheet, so I can't really add the USI node properly
there, nor I can test that. I guess it should be done separately from
this patch series.

Chanho, Krzysztof:

Guys, what are your thoughts on this? Basically with this patch series
applied, Exynos Auto V9 serial might become not functional. New USI
node should be added for UART case in Exynos Auto V9 dtsi (providing
correct sysreg, SW_CONF offset, clocks, etc), and serial node should
be encapsulated inside of that USI node. Also, USI node should be
referenced and enabled in SADK dts, providing also "clkreq-on"
property. More details can be found in [PATCH 1/5]. Do you think it's
ok to take this series as is, and add that later? Because otherwise we
might need to collaborate to add that Exynos Auto V9 enablement into
this patch series, which might take more time...

Thanks!

>
> --
> With Best Regards,
> Andy Shevchenko