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SubjectRE: [PATCH v3 0/5] soc: samsung: Add USI driver
Date
Hi,

> -----Original Message-----
> From: Sam Protsenko <semen.protsenko@linaro.org>
> Sent: Sunday, December 5, 2021 4:58 AM
> To: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>; Rob Herring
> <robh+dt@kernel.org>; Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Jaewon Kim <jaewon02.kim@samsung.com>; Chanho Park
> <chanho61.park@samsung.com>; David Virag <virag.david003@gmail.com>;
> Youngmin Nam <youngmin.nam@samsung.com>; devicetree@vger.kernel.org;
> linux-serial@vger.kernel.org; linux-arm-kernel@lists.infradead.org; linux-
> kernel@vger.kernel.org; linux-samsung-soc@vger.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@samsung.com> with below patch.
https://lore.kernel.org/linux-samsung-soc/20211208003946.139423-1-chanho61.p
ark@samsung.com/T/#u

Thanks.

Best Regards,
Chanho Park

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