[PATCH] i2c: mvtwsi: Swab the register address if its size is > 1

[Stefan Roese]

Hi Heiko,

On 11/18/21 09:18, Stefan Roese wrote:
> Testing on Armada XP with an EEPROM using register address with size
> of 2 has shown, that the register address bytes are sent to the I2C
> EEPROM in the incorrect order. This patch swabs the address bytes so
> that the correct address is transferred to the I2C device.
> 
> BTW: This worked without any issues before migrating Armada XP to
> DM I2C.
> 
> Signed-off-by: Stefan Roese <sr at denx.de>
> Cc: Heiko Schocher <hs at denx.de>
> Cc: Samuel Holland <samuel at sholland.org>
> Cc: Baruch Siach <baruch at tkos.co.il>
> Cc: Pali Rohár <pali at kernel.org>
> Cc: Marek Behún <marek.behun at nic.cz>
> ---
> It would be good if other users of this I2C driver could test this change
> with e.g. I2C EEPROM devices using 2 bytes (or more) for addressing.

Could you and other please take a look at this? Would be great, if this
could be pulled in the next merge window.

Thanks,
Stefan

>   drivers/i2c/mvtwsi.c | 12 ++++++++++--
>   1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/i2c/mvtwsi.c b/drivers/i2c/mvtwsi.c
> index 236bfb8d8e7f..ff21e3c52b58 100644
> --- a/drivers/i2c/mvtwsi.c
> +++ b/drivers/i2c/mvtwsi.c
> @@ -860,6 +860,9 @@ static int mvtwsi_i2c_xfer(struct udevice *bus, struct i2c_msg *msg, int nmsgs)
>   {
>   	struct mvtwsi_i2c_dev *dev = dev_get_priv(bus);
>   	struct i2c_msg *dmsg, *omsg, dummy;
> +	u8 *addr_buf_ptr;
> +	u8 addr_buf[4];
> +	int i;
>   
>   	memset(&dummy, 0, sizeof(struct i2c_msg));
>   
> @@ -873,12 +876,17 @@ static int mvtwsi_i2c_xfer(struct udevice *bus, struct i2c_msg *msg, int nmsgs)
>   	omsg = nmsgs == 1 ? &dummy : msg;
>   	dmsg = nmsgs == 1 ? msg : msg + 1;
>   
> +	/* We need to swap the register address if its size is > 1 */
> +	addr_buf_ptr = &addr_buf[0];
> +	for (i = omsg->len; i > 0; i--)
> +		*addr_buf_ptr++ = omsg->buf[i - 1];
> +
>   	if (dmsg->flags & I2C_M_RD)
> -		return __twsi_i2c_read(dev->base, dmsg->addr, omsg->buf,
> +		return __twsi_i2c_read(dev->base, dmsg->addr, addr_buf,
>   				       omsg->len, dmsg->buf, dmsg->len,
>   				       dev->tick);
>   	else
> -		return __twsi_i2c_write(dev->base, dmsg->addr, omsg->buf,
> +		return __twsi_i2c_write(dev->base, dmsg->addr, addr_buf,
>   					omsg->len, dmsg->buf, dmsg->len,
>   					dev->tick);
>   }
> 

Viele Grüße,
Stefan Roese

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