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Message-ID: <d074880a-14dd-46e4-852c-0bb068154603@linaro.org>
Date: Mon, 29 Apr 2024 08:33:31 +0200
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Subject: Re: [PATCH 3/7] i2c: muxes: add support for mule i2c multiplexer
To: Farouk Bouabid <farouk.bouabid@theobroma-systems.com>,
 Wolfram Sang <wsa+renesas@sang-engineering.com>,
 Peter Rosin <peda@axentia.se>, Andi Shyti <andi.shyti@kernel.org>,
 Rob Herring <robh@kernel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
 Conor Dooley <conor+dt@kernel.org>,
 Quentin Schulz <quentin.schulz@theobroma-systems.com>,
 Heiko Stuebner <heiko@sntech.de>
Cc: linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org,
 devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
 linux-rockchip@lists.infradead.org
References: <20240426-dev-mule-i2c-mux-v1-0-045a482f6ffb@theobroma-systems.com>
 <20240426-dev-mule-i2c-mux-v1-3-045a482f6ffb@theobroma-systems.com>
From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
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In-Reply-To: <20240426-dev-mule-i2c-mux-v1-3-045a482f6ffb@theobroma-systems.com>
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On 26/04/2024 18:49, Farouk Bouabid wrote:
> Mule is an mcu that emulates a set of i2c devices which are reacheable
> through an i2c-mux.
> 
> The emulated devices share a single i2c address with the mux itself where
> the requested register is what determines which logic is executed (mux or
> device):
> 
> 1- The devices on the mux can be selected (mux function) by writing the
> appropriate device number to an i2c config register (0xff) that is not
> used by any device logic.
> 
> 2- Any access to a register other than the config register will be
> handled by the previously selected device.
> 
> Signed-off-by: Farouk Bouabid <farouk.bouabid@theobroma-systems.com>
> ---
>  drivers/i2c/muxes/Kconfig        |  11 +++
>  drivers/i2c/muxes/Makefile       |   1 +
>  drivers/i2c/muxes/i2c-mux-mule.c | 157 +++++++++++++++++++++++++++++++++++++++
>  3 files changed, 169 insertions(+)
> 
> diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
> index db1b9057612a..593a20a6ac51 100644
> --- a/drivers/i2c/muxes/Kconfig
> +++ b/drivers/i2c/muxes/Kconfig
> @@ -119,4 +119,15 @@ config I2C_MUX_MLXCPLD
>  	  This driver can also be built as a module.  If so, the module
>  	  will be called i2c-mux-mlxcpld.
>  
> +config I2C_MUX_MULE
> +	tristate "Mule I2C device multiplexer"
> +	depends on OF
> +	help
> +	  If you say yes to this option, support will be included for a
> +	  Mule I2C device multiplexer. This driver provides access to
> +	  I2C devices connected on the Mule I2C mux.

Describe what is Mule. Here and in bindings documentation.

> +
> +	  This driver can also be built as a module.  If so, the module
> +	  will be called i2c-mux-mule.
> +
>  endmenu
> diff --git a/drivers/i2c/muxes/Makefile b/drivers/i2c/muxes/Makefile
> index 6d9d865e8518..4b24f49515a7 100644
> --- a/drivers/i2c/muxes/Makefile
> +++ b/drivers/i2c/muxes/Makefile
> @@ -10,6 +10,7 @@ obj-$(CONFIG_I2C_MUX_GPIO)	+= i2c-mux-gpio.o
>  obj-$(CONFIG_I2C_MUX_GPMUX)	+= i2c-mux-gpmux.o
>  obj-$(CONFIG_I2C_MUX_LTC4306)	+= i2c-mux-ltc4306.o
>  obj-$(CONFIG_I2C_MUX_MLXCPLD)	+= i2c-mux-mlxcpld.o
> +obj-$(CONFIG_I2C_MUX_MULE)	+= i2c-mux-mule.o
>  obj-$(CONFIG_I2C_MUX_PCA9541)	+= i2c-mux-pca9541.o
>  obj-$(CONFIG_I2C_MUX_PCA954x)	+= i2c-mux-pca954x.o
>  obj-$(CONFIG_I2C_MUX_PINCTRL)	+= i2c-mux-pinctrl.o
> diff --git a/drivers/i2c/muxes/i2c-mux-mule.c b/drivers/i2c/muxes/i2c-mux-mule.c
> new file mode 100644
> index 000000000000..da2a9526522e
> --- /dev/null
> +++ b/drivers/i2c/muxes/i2c-mux-mule.c
> @@ -0,0 +1,157 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Mule I2C device multiplexer
> + *
> + * Copyright (C) 2024 Theobroma Systems Design und Consulting GmbH
> + */
> +
> +#include <linux/i2c-mux.h>
> +#include <linux/i2c.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/property.h>
> +#include <linux/regmap.h>
> +
> +#define MUX_CONFIG_REG	0xff
> +#define MUX_DEFAULT_DEV	0x0
> +
> +struct mule_i2c_reg_mux {
> +	struct regmap *regmap;
> +};
> +
> +static const struct regmap_config mule_regmap_config = {
> +	.reg_bits = 8,
> +	.val_bits = 8,
> +};
> +
> +static const struct of_device_id mule_i2c_mux_of_match[] = {
> +	{.compatible = "tsd,mule-i2c-mux",},
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, mule_i2c_mux_of_match);

This goes after or before probe. Don't introduce unusual coding style.

> +

..

> +static void mux_remove(void *data)
> +{
> +	struct i2c_mux_core *muxc = data;
> +
> +	i2c_mux_del_adapters(muxc);
> +
> +	mux_deselect(muxc, MUX_DEFAULT_DEV);
> +}
> +
> +static int mule_i2c_mux_probe(struct i2c_client *client)
> +{
> +	struct i2c_adapter *adap = client->adapter;
> +	struct mule_i2c_reg_mux *priv;
> +	struct i2c_mux_core *muxc;
> +	struct device_node *dev;
> +	unsigned int readback;
> +	bool old_fw;
> +	int ndev, ret;
> +
> +	/* Count devices on the mux */
> +	ndev = of_get_child_count(client->dev.of_node);
> +	dev_dbg(&client->dev, "%u devices on the mux\n", ndev);
> +
> +	muxc = i2c_mux_alloc(adap, &client->dev,
> +						 ndev, sizeof(*priv),
> +						 I2C_MUX_LOCKED,
> +						 mux_select, mux_deselect);

Very odd alignment. This is absolutely unreadable.

Please properly align with opening (.

> +	if (!muxc)
> +		return -ENOMEM;
> +
> +	muxc->share_addr_with_children = 1;
> +	priv = i2c_mux_priv(muxc);
> +
> +	priv->regmap = devm_regmap_init_i2c(client, &mule_regmap_config);
> +	if (IS_ERR(priv->regmap))
> +		return dev_err_probe(&client->dev, PTR_ERR(priv->regmap),
> +							 "Failed to allocate i2c register map\n");
> +
> +	i2c_set_clientdata(client, muxc);
> +
> +	/*
> +	 * Mux 0 is guaranteed to exist on all old and new mule fw.
> +	 * mule fw without mux support will accept write ops to the
> +	 * config register, but readback returns 0xff (register not updated).
> +	 */
> +	ret = mux_select(muxc, 0);
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_read(priv->regmap, MUX_CONFIG_REG, &readback);
> +	if (ret)
> +		return ret;
> +
> +	old_fw = (readback == 0);
> +
> +	ret = devm_add_action_or_reset(&client->dev, mux_remove, muxc);

This is really odd. Why do you call remove callback as devm action?

I have serious doubts this was really tested.

> +	if (ret)
> +		return ret;
> +
> +	/* Create device adapters */
> +	for_each_child_of_node(client->dev.of_node, dev) {
> +		u32 reg;
> +
> +		ret = of_property_read_u32(dev, "reg", &reg);
> +		if (ret) {
> +			dev_err(&client->dev, "No reg property found for %s: %d\n",
> +					of_node_full_name(dev), ret);

Very odd alignment. Please properly align with opening (.

> +			return ret;
> +		}
> +
> +		if (!old_fw && reg != 0) {
> +			dev_warn(&client->dev,
> +					 "Mux %d not supported, please update Mule FW\n", reg);
> +			continue;
> +		}
> +
> +		ret = mux_select(muxc, reg);
> +		if (ret) {
> +			dev_warn(&client->dev,
> +					 "Mux %d not supported, please update Mule FW\n", reg);
> +			continue;
> +		}
> +
> +		ret = i2c_mux_add_adapter(muxc, 0, reg, 0);
> +		if (ret) {
> +			dev_err(&client->dev, "Failed to add i2c mux adapter %d: %d\n", reg, ret);
> +			return ret;
> +		}
> +	}
> +
> +	mux_deselect(muxc, MUX_DEFAULT_DEV);
> +
> +	return 0;
> +}
> +
> +static struct i2c_driver mule_i2c_mux_driver = {
> +	.driver		= {
> +		.name	= "mule-i2c-mux",
> +		.of_match_table = mule_i2c_mux_of_match,
> +	},
> +	.probe		= mule_i2c_mux_probe,
> +};
> +

Anyway, all this looks like i2c-mux-reg. Please provide rationale in
commit msg WHY you need one more driver.


Best regards,
Krzysztof