Re: [PATCH 2/2] tpm: tis_i2c: Limit write bursts to I2C_SMBUS_BLOCK_MAX (32) bytes

[Jerry Snitselaar]

On Wed, May 24, 2023 at 05:40:40PM +0200, A. Sverdlin wrote:
> From: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxxxx>
> 
> Underlying I2C bus drivers not always support longer transfers and
> imx-lpi2c for instance doesn't. The fix is symmetric to previous patch
> which fixed the read direction.
> 
> Fixes: bbc23a07b072 ("tpm: Add tpm_tis_i2c backend for tpm_tis_core")
> Tested-by: Michael Haener <michael.haener@xxxxxxxxxxx>
> Signed-off-by: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxxxx>

Reviewed-by: Jerry Snitselaar <jsnitsel@xxxxxxxxxx>

> ---
>  drivers/char/tpm/tpm_tis_i2c.c | 22 +++++++++++++++-------
>  1 file changed, 15 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_tis_i2c.c b/drivers/char/tpm/tpm_tis_i2c.c
> index 106fd20d94e4..82fda488e98b 100644
> --- a/drivers/char/tpm/tpm_tis_i2c.c
> +++ b/drivers/char/tpm/tpm_tis_i2c.c
> @@ -230,19 +230,27 @@ static int tpm_tis_i2c_write_bytes(struct tpm_tis_data *data, u32 addr, u16 len,
>  	struct i2c_msg msg = { .addr = phy->i2c_client->addr };
>  	u8 reg = tpm_tis_i2c_address_to_register(addr);
>  	int ret;
> +	u16 wrote = 0;
>  
>  	if (len > TPM_BUFSIZE - 1)
>  		return -EIO;
>  
> -	/* write register and data in one go */
>  	phy->io_buf[0] = reg;
> -	memcpy(phy->io_buf + sizeof(reg), value, len);
> -
> -	msg.len = sizeof(reg) + len;
>  	msg.buf = phy->io_buf;
> -	ret = tpm_tis_i2c_retry_transfer_until_ack(data, &msg);
> -	if (ret < 0)
> -		return ret;
> +	while (wrote < len) {
> +		/* write register and data in one go */
> +		msg.len = sizeof(reg) + len - wrote;
> +		if (msg.len > I2C_SMBUS_BLOCK_MAX)
> +			msg.len = I2C_SMBUS_BLOCK_MAX;
> +
> +		memcpy(phy->io_buf + sizeof(reg), value + wrote,
> +		       msg.len - sizeof(reg));
> +
> +		ret = tpm_tis_i2c_retry_transfer_until_ack(data, &msg);
> +		if (ret < 0)
> +			return ret;
> +		wrote += msg.len - sizeof(reg);
> +	}
>  
>  	return 0;
>  }
> -- 
> 2.40.1
>