linux-kernel - RE: [PATCH v3 0/5] soc: samsung: Add USI driver

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Date:   Wed, 8 Dec 2021 18:15:57 +0900
From:   "Chanho Park" <chanho61.park@...sung.com>
To:     "'Sam Protsenko'" <semen.protsenko@...aro.org>,
        "'Krzysztof Kozlowski'" <krzysztof.kozlowski@...onical.com>,
        "'Rob Herring'" <robh+dt@...nel.org>,
        "'Greg Kroah-Hartman'" <gregkh@...uxfoundation.org>
Cc:     "'Jaewon Kim'" <jaewon02.kim@...sung.com>,
        "'David Virag'" <virag.david003@...il.com>,
        "'Youngmin Nam'" <youngmin.nam@...sung.com>,
        <devicetree@...r.kernel.org>, <linux-serial@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-samsung-soc@...r.kernel.org>
Subject: RE: [PATCH v3 0/5] soc: samsung: Add USI driver

Hi,

> -----Original Message-----
> From: Sam Protsenko <semen.protsenko@...aro.org>
> Sent: Sunday, December 5, 2021 4:58 AM
> To: Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>; Rob Herring
> <robh+dt@...nel.org>; Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Jaewon Kim <jaewon02.kim@...sung.com>; Chanho Park
> <chanho61.park@...sung.com>; David Virag <virag.david003@...il.com>;
> Youngmin Nam <youngmin.nam@...sung.com>; devicetree@...r.kernel.org;
> linux-serial@...r.kernel.org; linux-arm-kernel@...ts.infradead.org; linux-
> kernel@...r.kernel.org; linux-samsung-soc@...r.kernel.org
> Subject: [PATCH v3 0/5] soc: samsung: Add USI driver
> 
> USIv2 IP-core provides selectable serial protocol (UART, SPI or High-Speed
> I2C); only one can be chosen at a time. This series implements USIv2
> driver, which allows one to select particular USI function in device tree,
> and also performs USI block initialization.
> 
> With that driver implemented, it's not needed to do USI initialization in
> protocol drivers anymore, so that code is removed from the serial driver.
> 
> Because USI driver is tristate (can be built as a module), serial driver
> was reworked so it's possible to use its console part as a module too.
> This way we can load serial driver module from user space and still have
> serial console functional.
> 
> Design features:
>   - "reg" property contains USI registers start address (0xc0 offset);
>     it's used in the driver to access USI_CON and USI_OPTION registers.
>     This way all USI initialization (reset, HWACG, etc) can be done in
>     USIv2 driver separately, rather than duplicating that code over
>     UART/SPI/I2C drivers
>   - System Register (system controller node) and its SW_CONF register
>     offset are provided in "samsung,sysreg" property; it's used to
>     select USI function (protocol to be used)
>   - USI function is specified in "samsung,mode" property; integer value
>     is used to simplify parsing
>   - there is "samsung,clkreq-on" bool property, which makes driver
>     disable HWACG control (needed for UART to work properly)
>   - PCLK and IPCLK clocks are both provided to USI node; apparently both
>     need to be enabled to access USI registers
>   - protocol nodes are embedded (as a child nodes) in USI node; it
>     allows correct init order, and reflects HW properly
>   - USI driver is a tristate: can be also useful from Android GKI
>     requirements point of view
>   - driver functions are implemented with further development in mind:
>     - we might want to add some DebugFs interface later
>     - some functions might need to be revealed to serial drivers with
>       EXPORT_SYMBOL(), and provide somehow pointer to needed USI driver
>       instance
>     - another USI revisions could be added (like USIv1)
> 
> Changes in v3:
>   - Renamed compatible from samsung,exynos-usi-v2 to samsung,exynos850-usi
>   - Used clk_bulk API instead of handling each clock separately
>   - Spell check fixes and coding style fixes
>   - Improved dt-bindings doc
> 
> Changes in v2:
>   - Renamed all 'usi_v2' wording to just 'usi' everywhere
>   - Removed patches adding dependency on EXYNOS_USI for UART/I2C/SPI
>     drivers
>   - Added patch: "tty: serial: samsung: Fix console registration from
>     module"
>   - Combined dt-bindings doc and dt-bindings header patches
>   - Reworked USI driver to be ready for USIv1 addition
>   - Improved dt-bindings
>   - Added USI_V2_NONE mode value
> 
> Sam Protsenko (5):
>   dt-bindings: soc: samsung: Add Exynos USI bindings
>   soc: samsung: Add USI driver
>   tty: serial: samsung: Remove USI initialization
>   tty: serial: samsung: Enable console as module
>   tty: serial: samsung: Fix console registration from module

Tested-by: Chanho Park <chanho61.park@...sung.com> with below patch.
https://lore.kernel.org/linux-samsung-soc/20211208003946.139423-1-chanho61.p
ark@...sung.com/T/#u

Thanks.

Best Regards,
Chanho Park