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Date:   Sat, 30 May 2020 23:06:09 +0200
From:   Wolfram Sang <>
To:     Serge Semin <>
Cc:     Jarkko Nikula <>,
        Serge Semin <>,
        Alexey Malahov <>,
        Maxim Kaurkin <>,
        Pavel Parkhomenko <>,
        Ramil Zaripov <>,
        Ekaterina Skachko <>,
        Vadim Vlasov <>,
        Alexey Kolotnikov <>,
        Thomas Bogendoerfer <>,
        Andy Shevchenko <>,
        Mika Westerberg <>,
        Rob Herring <>,,,,
Subject: Re: [PATCH v6 00/11] i2c: designeware: Add Baikal-T1 System I2C

On Thu, May 28, 2020 at 12:33:10PM +0300, Serge Semin wrote:
> Jarkko, Wolfram, the merge window is upon us, please review/merge in/whatever
> the patchset.
> Initially this has been a small patchset which embedded the Baikal-T1
> System I2C support into the DW APB I2C driver as is by using a simplest
> way. After a short discussion with Andy we decided to implement what he
> suggested (introduce regmap-based accessors and create a glue driver) and
> even more than that to provide some cleanups of the code. So here is what
> this patchset consists of.
> First of all we've found out that current implementation of scripts/dtc
> didn't support i2c dt nodes with 10bit and slave flags set in the
> reg property. You'll see an error if you try to dt_binding_check it.
> So the very first patch fixes the problem by adding these flags support
> into the check_i2c_bus_reg() method.
> Traditionally we converted the plain text-based DT binding to the DT schema
> and added Baikal-T1 System I2C device support there. This required to mark
> the reg property redundant for Baikal-T1 I2C since its reg-space is
> indirectly accessed by means of the System Controller cmd/read/write
> registers.
> Then as Andy suggested we replaced the Synopsys DW APB I2C common driver
> registers IO accessors into the regmap API methods. This doesn't change
> the code logic much, though in two places we managed to replace some bulky
> peaces of code with a ready-to-use regmap methods.
> Additionally before adding the glue layer API we initiated a set of cleanups:
> - Define components of the multi-object drivers (like i2c-designware-core.o
>   and i2c-designware-paltform.o) with using `-y` suffixed makefile
>   variables instead of `-objs` suffixed one. This is encouraged by
>   Documentation/kbuild/makefiles.rst text since `-objs` is supposed to be used
>   to build host programs.
> - Make DW I2C slave driver depended on the DW I2C core code instead of the
>   platform one, which it really is.
> - Move Intel Baytrail semaphore feature to the platform if-clause of the
>   kernel config.
> After this we finally can introduce the glue layer API for the DW APB I2C
> platform driver. So there are three methods exported from the driver:
> i2c_dw_plat_setup(), i2c_dw_plat_clear(), &i2c_dw_plat_dev_pm_ops to
> setup, cleanup and add PM operations to the glue driven I2C device. Before
> setting the platform DW I2C device up the glue probe code is supposed to
> create an instance of DW I2C device generic object and pre-initialize
> its `struct device` pointer together with optional platform-specific
> flags. In addition to that we converted the MSCC Ocelot SoC I2C specific
> code into the glue layer seeing it's really too specific and, which is more
> important, isn't that complicated so we could unpin it without much of
> worrying to break something.
> Meanwhile we discovered that MODEL_CHERRYTRAIL and MODEL_MASK actually
> were no longer used in the code. MODEL_MSCC flag has been discarded since
> the MSCC Ocelot I2C code conversion to the glue driver. So now we can get
> rid of all the MODEL-specific flags.
> Finally we introduced a glue driver with Baikal-T1 System I2C device
> support. The driver probe tries to find a syscon regmap, creates the DW
> APB I2C regmap based on it and passes it further to the DW I2C device
> descriptor. Then it does normal DW APB I2C platform setup by calling a
> generic setup method. Cleanup is straightforward. It's just calling a
> generic DW APB I2C clean method.
> This patchset is rebased and tested on the i2c/for-next (5.7-rc4):
> base-commit: 2a41d0f91443 Merge branch 'i2c/for-5.8' into i2c/for-next
> Note new vendor prefix for Baikal-T1 System I2C device is added in the
> framework of the next patchset:
> Changelog v2:
> - Fix the SoB tags.
> - Use a shorter summary describing the bindings convertion patch.
> - Patch "i2c: designware: Detect the FIFO size in the common code" has
>   been acked by Jarkko and applied by Wolfram to for-next so drop it from
>   the set.
> - Patch "i2c: designware: Discard i2c_dw_read_comp_param() function" has
>   been acked by Jarkko and applied by Wolfram to for-next so drop it from
>   the set.
> - Make sure that "mscc,ocelot-i2c" compatible node may have up to two
>   registers space defined in the DT node, while normal DW I2C controller
>   will have only one registers space.
> - Add "mscc,ocelot-i2c" DT schema example to test the previous fix.
> - Declare "unevaluatedProperties" property instead of
>   "additionalProperties" one in the DT schema.
> - Due to the previous fix we can now discard the dummy boolean properties
>   declaration, since the proper type evaluation will be performed by the
>   generic i2c-controller.yaml schema.
> - Refactor the DW I2C APB driver related series to address the Andies
>   notes.
> - Convert DW APB I2C driver to using regmap instead of handwritten
>   accessors.
> - Use `-y` to build multi-object DW APB drivers.
> - Fix DW APB I2C slave code dependency. It should depend on
> - Move Baytrail semaphore config to the platform if-clause.
> - Introduce a glue-layer platform driver API.
> - Unpin Microsemi Ocelot I2C code into a glue driver.
> - Remove MODEL_CHERRYTRAIL and MODEL_MASK as no longer needed.
> - Add support for custom regmap passed from glue driver.
> - Add Baikal-T1 System I2C support in a dedicated glue layer driver.
> Link:
> Changelog v3:
> - Move fixes and less invasive patches to the head of the series.
> - Add patch "dt-bindings: i2c: Discard i2c-slave flag from the DW I2C
>   example" since Rob says the flag can be discarded until dtc is fixed.
> - Add patch "i2c: designware: Retrieve quirk flags as early as possible"
>   as a first preparation before adding Baikal-T1 System I2C support.
> - Add patch "i2c: designware: Move reg-space remapping into a dedicated
>   function" as a second preparation before adding Baikal-T1 System I2C
>   support.
> - Add patch "i2c: designware: Add Baikal-T1 System I2C support", which
>   integrates the Baikal-T1 I2C support into the DW I2C platform driver.
> - Get back the reg property being mandatory even if it's Baikal-T1 System
>   I2C DT node. Rob says it has to be in the DT node if there is a
>   dedicated registers range in the System Controller registers space.
> - Replace if-endif clause around the I2C_DESIGNWARE_BAYTRAIL config
>   with "depends on" operator.
> Link:
> Changelog v4:
> - Rebase on top of the i2c/for-next branch.
> - Use PTR_ERR_OR_ZERO() helper in the bt1_i2c_request_regs() and
>   in the dw_i2c_plat_request_regs() methods.
> - Discard devm_platform_get_and_ioremap_resource() utilization.
> - Discard patch "scripts/dtc: check: Add 10bit/slave i2c reg flags
>   support" since it must be merged in to the dtc upstream repository.
> Link:
> Changelog v5:
> - Replace or-assignment with just assignment operator when getting
>   the quirk flags.
> - Keep alphabetical order of the include statements.
> - Discard explicit u16-type cast in the dw_reg_write_word() method.
> Link:
> Changelog v6:
> - Add commas after the last member of the regmap_config instances
>   initializers.
> - Replace the "linux,slave-24c02" compatible string with "atmel,24c02" one
>   so the DT example would be perceived as a normal DW I2C master mode.
> Signed-off-by: Serge Semin <>
> Cc: Alexey Malahov <>
> Cc: Maxim Kaurkin <>
> Cc: Pavel Parkhomenko <>
> Cc: Ramil Zaripov <>
> Cc: Ekaterina Skachko <>
> Cc: Vadim Vlasov <>
> Cc: Alexey Kolotnikov <>
> Cc: Thomas Bogendoerfer <>
> Cc: Andy Shevchenko <>
> Cc: Mika Westerberg <>
> Cc: Rob Herring <>
> Cc:
> Cc:
> Cc:
> Cc:
> Serge Semin (11):
>   dt-bindings: i2c: Convert DW I2C binding to DT schema
>   dt-bindings: i2c: Convert DW I2C slave to the DW I2C master example
>   dt-bindings: i2c: dw: Add Baikal-T1 SoC I2C controller
>   i2c: designware: Use `-y` to build multi-object modules
>   i2c: designware: slave: Set DW I2C core module dependency
>   i2c: designware: Add Baytrail sem config DW I2C platform dependency
>   i2c: designware: Discard Cherry Trail model flag
>   i2c: designware: Convert driver to using regmap API
>   i2c: designware: Retrieve quirk flags as early as possible
>   i2c: designware: Move reg-space remapping into a dedicated function
>   i2c: designware: Add Baikal-T1 System I2C support

Applied to for-next, thanks!

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