linux-kernel - Re: [PATCH v3 3/7] i2c: muxes: add support for mule i2c multiplexer

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Date: Tue, 11 Jun 2024 19:56:03 +0200
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Farouk Bouabid <farouk.bouabid@...rry.de>,
 Wolfram Sang <wsa+renesas@...g-engineering.com>,
 Peter Rosin <peda@...ntia.se>, Andi Shyti <andi.shyti@...nel.org>,
 Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, Quentin Schulz
 <quentin.schulz@...rry.de>, Heiko Stuebner <heiko@...ech.de>
Cc: linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
 devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH v3 3/7] i2c: muxes: add support for mule i2c multiplexer

Le 11/06/2024 à 13:43, Farouk Bouabid a écrit :
> Mule is an MCU that emulates a set of I2C devices which are reachable
> 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 logic or device logic):
> 
> 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@...rry.de>
> ---

Hi,

...

> +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;
> +	int ndev, ret;
> +	bool old_fw;
> +
> +	/* 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);

Should this be %d?

> +
> +	muxc = i2c_mux_alloc(adap, &client->dev,
> +			     ndev, sizeof(*priv),
> +			     I2C_MUX_LOCKED,
> +			     mux_select, mux_deselect);

Nitpick: this could be written with less lines.

> +	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);

Should this 0 be MUX_DEFAULT_DEV (for consistency)?

> +	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);
> +	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);

return dev_err_probe() as above?

> +			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 dev_err_probe() as above?

> +			return ret;
> +		}
> +	}
> +
> +	mux_deselect(muxc, MUX_DEFAULT_DEV);
> +
> +	return 0;
> +}

...