linux-kernel - Re: [PATCH v5 08/11] i2c: designware: Convert driver to using regmap API

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Date:   Wed, 27 May 2020 19:03:37 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        Wolfram Sang <wsa@...-dreams.de>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-mips@...r.kernel.org, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 08/11] i2c: designware: Convert driver to using regmap
 API

On Wed, May 27, 2020 at 06:30:43PM +0300, Serge Semin wrote:
> Seeing the DW I2C driver is using flags-based accessors with two
> conditional clauses it would be better to replace them with the regmap
> API IO methods and to initialize the regmap object with read/write
> callbacks specific to the controller registers map implementation. This
> will be also handy for the drivers with non-standard registers mapping
> (like an embedded into the Baikal-T1 System Controller DW I2C block, which
> glue-driver is a part of this series).
> 
> As before the driver tries to detect the mapping setup at probe stage and
> creates a regmap object accordingly, which will be used by the rest of the
> code to correctly access the controller registers. In two places it was
> appropriate to convert the hand-written read-modify-write and
> read-poll-loop design patterns to the corresponding regmap API
> ready-to-use methods.
> 
> Note the regmap IO methods return value is checked only at the probe
> stage. The rest of the code won't do this because basically we have
> MMIO-based regmap so non of the read/write methods can fail (this also
> won't be needed for the Baikal-T1-specific I2C controller).

...

> +	struct regmap_config map_cfg = {
> +		.reg_bits = 32,
> +		.val_bits = 32,
> +		.reg_stride = 4,
> +		.disable_locking = true,
> +		.reg_read = dw_reg_read,
> +		.reg_write = dw_reg_write,

> +		.max_register = DW_IC_COMP_TYPE

Perhaps leave comma here as well.

> +	};

...

> +	/*
> +	 * Note we'll check the return value of the regmap IO accessors only
> +	 * at the probe stage. The rest of the code won't do this because
> +	 * basically we have MMIO-based regmap so non of the read/write methods
> +	 * can fail.
> +	 */
> +	dev->map = devm_regmap_init(dev->dev, NULL, dev, &map_cfg);
> +	if (IS_ERR(dev->map)) {
> +		dev_err(dev->dev, "Failed to init the registers map\n");

> +		return PTR_ERR(dev->map);
> +	}
> +
>  	return 0;

	return PTR_ERR_OR_ZERO(dev->map);

-- 
With Best Regards,
Andy Shevchenko