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From:   Luca Ceresoli <luca@lucaceresoli.net>
Subject: Re: [RFC PATCH v2 5/6] i2c: of: mark a whole array of regs as
 reserved
To:     Wolfram Sang <wsa+renesas@sang-engineering.com>,
        linux-i2c@vger.kernel.org
Cc:     linux-renesas-soc@vger.kernel.org, linux-i3c@lists.infradead.org,
        Kieran Bingham <kieran@ksquared.org.uk>,
        =?UTF-8?Q?Niklas_S=c3=b6derlund?= <niklas.soderlund@ragnatech.se>,
        Jacopo Mondi <jacopo@jmondi.org>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Vladimir Zapolskiy <vz@mleia.com>, linux-kernel@vger.kernel.org
References: <20200318150059.21714-1-wsa+renesas@sang-engineering.com>
 <20200318150059.21714-6-wsa+renesas@sang-engineering.com>
Message-ID: <578266c3-1bfb-2d7a-6d95-d40b3d8cd3ab@lucaceresoli.net>
Date:   Wed, 15 Apr 2020 12:07:20 +0200
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Hi,

 18/03/20 16:00, Wolfram Sang wrote:
> Back then, 'reg' properties in I2C DT bindings only contained one
> address and this address was assigned a device and, thus, blocked.
> Meanwhile, chips using multiple addresses are common and the 'reg'
> property can be an array described by 'reg-names'. This code enhances
> I2C DT parsing, so it will reserve all addresses described in an array.
> They will be bound to the 'dummy' driver as 'reserved' iff the first
> address can be assigned successfully. If that is not the case, the array
> is not further considered. If one later address of the array can not be
> assigned, it will be reported but we don't bail out. The driver has to
> decide if that address is critical or not.
> 
> Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
> ---
>  drivers/i2c/i2c-core-of.c | 70 +++++++++++++++++++++++++--------------
>  1 file changed, 46 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/i2c/i2c-core-of.c b/drivers/i2c/i2c-core-of.c
> index f2d09ea0d336..67eb2cd305cf 100644
> --- a/drivers/i2c/i2c-core-of.c
> +++ b/drivers/i2c/i2c-core-of.c
> @@ -16,25 +16,18 @@
>  #include <linux/i2c.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
> +#include <linux/of_address.h>
>  #include <linux/of_device.h>
>  #include <linux/sysfs.h>
>  
>  #include "i2c-core.h"
>  
> -int of_i2c_get_board_info(struct device_node *node, struct i2c_board_info *info)
> +static void of_i2c_decode_board_info(struct device_node *node, u32 addr,
> +				     bool first_addr, struct i2c_board_info *info)
>  {
> -	u32 addr;
> -	int ret;
> -
>  	memset(info, 0, sizeof(*info));
>  
> -	ret = of_property_read_u32(node, "reg", &addr);
> -	if (ret) {
> -		pr_err("invalid reg on %pOF\n", node);
> -		return ret;
> -	}
> -
> -	if (of_modalias_node(node, info->type, sizeof(info->type)) < 0)
> +	if (!first_addr || of_modalias_node(node, info->type, sizeof(info->type)) < 0)
>  		strlcpy(info->type, I2C_RESERVED_DRV_NAME, sizeof(I2C_RESERVED_DRV_NAME));
>  
>  	if (addr & I2C_TEN_BIT_ADDRESS) {
> @@ -51,11 +44,27 @@ int of_i2c_get_board_info(struct device_node *node, struct i2c_board_info *info)
>  	info->of_node = node;
>  	info->fwnode = of_fwnode_handle(node);
>  
> -	if (of_property_read_bool(node, "host-notify"))
> -		info->flags |= I2C_CLIENT_HOST_NOTIFY;
> +	if (first_addr) {
> +		if (of_property_read_bool(node, "host-notify"))
> +			info->flags |= I2C_CLIENT_HOST_NOTIFY;
> +
> +		if (of_get_property(node, "wakeup-source", NULL))
> +			info->flags |= I2C_CLIENT_WAKE;
> +	}
> +}
> +
> +int of_i2c_get_board_info(struct device_node *node, struct i2c_board_info *info)
> +{
> +	u32 addr;
> +	int ret;
> +
> +	ret = of_property_read_u32(node, "reg", &addr);
> +	if (ret) {
> +		pr_err("invalid reg on %pOF\n", node);
> +		return ret;
> +	}
>  
> -	if (of_get_property(node, "wakeup-source", NULL))
> -		info->flags |= I2C_CLIENT_WAKE;
> +	of_i2c_decode_board_info(node, addr, true, info);
>  
>  	return 0;
>  }
> @@ -64,21 +73,34 @@ EXPORT_SYMBOL_GPL(of_i2c_get_board_info);
>  static struct i2c_client *of_i2c_register_device(struct i2c_adapter *adap,
>  						 struct device_node *node)
>  {
> -	struct i2c_client *client;
> +	struct i2c_client *client, *first_client = ERR_PTR(-ENOENT);
>  	struct i2c_board_info info;
> -	int ret;
> +	bool first_reg = true;
> +	unsigned int i = 0;
> +	const __be32 *prop;
> +	u16 reg;
>  
>  	pr_debug("register %pOF\n", node);
>  
> -	ret = of_i2c_get_board_info(node, &info);
> -	if (ret)
> -		return ERR_PTR(ret);
> +	while ((prop = of_get_address(node, i++, NULL, NULL))) {
> +		reg = of_read_number(prop, 1);
> +		of_i2c_decode_board_info(node, reg, first_reg, &info);
> +
> +		client = i2c_new_client_device(adap, &info);
> +		if (IS_ERR(client)) {
> +			pr_err("failure registering addr 0x%02x for %pOF (%ld)\n",
> +				reg, node, PTR_ERR(client));
> +			if (first_reg)
> +				return client;
> +		}

I had an opportunity to runtime test this whole series on top of my TI
DS90UB95x serdes patches and it generally works fine.

I noticed however a minor annoyance in the above while loop. During
probing, these errors are produced:

  i2c i2c-0: Failed to register i2c client reserved at 0x40 (-16)
  i2c_of: failure registering addr 0x40 for /ocp/i2c@48070000/des_0@30 (-16)

This is logged as an error, so I assumed probing had failed, instead it
succeeded. This happens because the first loop iteration (on the first
'reg') triggers the driver's probe(), which in my case calls
i2c_new_ancillary_device() to register address 0x40. The second loop
iteration finds 0x40 in DT and tries to register it as "reserved", but
it fails. By design the loop continues successfully, but the (double)
error printed is misleading.

Fixing the second error, which comes from the above loop, is easy:

 client = i2c_new_client_device(adap, &info);
 if (IS_ERR(client)) {
-	pr_err("failure registering addr 0x%02x for %pOF (%ld)\n",
-		reg, node, PTR_ERR(client));
 	if (first_reg)
+		pr_err("failure registering addr 0x%02x for %pOF (%ld)\n",
+			reg, node, PTR_ERR(client));
 		return client;
 }

The other error is produced in i2c_new_client_device() and I see no
obvious way to put an if in front of the dev_err() except checking if
client->name equals I2C_RESERVED_DRV_NAME.

-- 
Luca