linux-kernel - Re: [PATCH v4 2/2] i2c: muxes: pca954x: Enable features on MAX7357

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <29485a37-1f45-9f7f-9cc5-5d6a9fcc5e08@axentia.se>
Date:   Fri, 6 Oct 2023 09:46:04 +0200
From:   Peter Rosin <peda@...ntia.se>
To:     Naresh Solanki <naresh.solanki@...ements.com>
Cc:     Patrick Rudolph <patrick.rudolph@...ements.com>,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/2] i2c: muxes: pca954x: Enable features on MAX7357

Hi!

2023-10-05 at 15:45, Naresh Solanki wrote:
> From: Patrick Rudolph <patrick.rudolph@...ements.com>
> 
> Enable additional features based on DT settings and unconditionally
> release the shared interrupt pin after 1.6 seconds and allow to use
> it as reset.
> 
> These features aren't enabled by default & its up to board designer
> to enable the same as it may have unexpected side effects.
> 
> These should be validated for proper functioning & detection of devices
> in secondary bus as sometimes it can cause secondary bus being disabled.
> 
> Signed-off-by: Patrick Rudolph <patrick.rudolph@...ements.com>
> Signed-off-by: Naresh Solanki <naresh.solanki@...ements.com>
> ---
> Changes in V4:
> - Drop max7358
> - Update #define
> - Move conf variable
> - Print warning when I2C_FUNC_SMBUS_WRITE_BYTE_DATA isn't supported
> Changes in V3:
> - Delete unused #define
> - Update pca954x_init
> - Update commit message
> 
> Changes in V2:
> - Update comments
> - Update check for DT properties
> ---
>  drivers/i2c/muxes/i2c-mux-pca954x.c | 44 ++++++++++++++++++++++++++++-
>  1 file changed, 43 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c
> index 2219062104fb..f37ce332078c 100644
> --- a/drivers/i2c/muxes/i2c-mux-pca954x.c
> +++ b/drivers/i2c/muxes/i2c-mux-pca954x.c
> @@ -57,6 +57,20 @@
>  
>  #define PCA954X_IRQ_OFFSET 4
>  
> +/*
> + * MAX7357's configuration register is writeable after POR, but
> + * can be locked by setting the basic mode bit. MAX7358 configuration
> + * register is locked by default and needs to be unlocked first.
> + * The configuration register holds the following settings:
> + */
> +#define MAX7357_CONF_INT_ENABLE			BIT(0)
> +#define MAX7357_CONF_FLUSH_OUT			BIT(1)
> +#define MAX7357_CONF_RELEASE_INT		BIT(2)
> +#define MAX7357_CONF_DISCON_SINGLE_CHAN		BIT(4)
> +#define MAX7357_CONF_PRECONNECT_TEST		BIT(7)
> +
> +#define MAX7357_POR_DEFAULT_CONF		MAX7357_CONF_INT_ENABLE
> +
>  enum pca_type {
>  	max_7356,
>  	max_7357,
> @@ -470,7 +484,35 @@ static int pca954x_init(struct i2c_client *client, struct pca954x *data)
>  	else
>  		data->last_chan = 0; /* Disconnect multiplexer */
>  
> -	ret = i2c_smbus_write_byte(client, data->last_chan);
> +	if (device_is_compatible(&client->dev, "maxim,max7357")) {
> +		if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WRITE_BYTE_DATA)) {
> +			u8 conf = MAX7357_POR_DEFAULT_CONF;
> +			/*
> +			 * The interrupt signal is shared with the reset pin. Release the
> +			 * interrupt after 1.6 seconds to allow using the pin as reset.
> +			 * The interrupt isn't serviced yet.

I'd suggest dropping the word "yet". The interrupt isn't serviced for
max7357, period. The "yet" in combination with that 1.6 second window is
a bit cunfusing and readers might think that the interrupt is serviced
at some later stage or something, when I think the intention of "The
interrupt isn't serviced yet" comes with the silent implication that it
is simply not implemented yet.

> +			 */
> +			conf |= MAX7357_CONF_RELEASE_INT;
> +
> +			if (device_property_read_bool(&client->dev, "maxim,isolate-stuck-channel"))
> +				conf |= MAX7357_CONF_DISCON_SINGLE_CHAN;
> +			if (device_property_read_bool(&client->dev,
> +						      "maxim,send-flush-out-sequence"))
> +				conf |= MAX7357_CONF_FLUSH_OUT;
> +			if (device_property_read_bool(&client->dev,
> +						      "maxim,preconnection-wiggle-test-enable"))
> +				conf |= MAX7357_CONF_PRECONNECT_TEST;
> +
> +			ret = i2c_smbus_write_byte_data(client, data->last_chan, conf);
> +		} else {
> +			dev_warn(&client->dev,
> +				 "Write byte not supported. Cannot enable enhanced mode features");

Missing \n at the end of the string.

Cheers,
Peter

> +			ret = i2c_smbus_write_byte(client, data->last_chan);
> +		}
> +	} else {
> +		ret = i2c_smbus_write_byte(client, data->last_chan);
> +	}
> +
>  	if (ret < 0)
>  		data->last_chan = 0;
>