Re: [PATCH v2] i2c: i2c-mxs: Use DMA mode even for small transfers

[Lucas Stach <l.stach-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>]

Am Montag, den 01.07.2013, 18:14 -0300 schrieb Fabio Estevam:
> From: Fabio Estevam <fabio.estevam-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
> 
> Recently we have been seing some reports about PIO mode not working properly.
> 
> - http://www.spinics.net/lists/linux-i2c/msg11985.html
> - http://marc.info/?l=linux-i2c&m=137235593101385&w=2
> - https://lkml.org/lkml/2013/6/24/430
> 
> Let's use DMA mode even for small transfers.
> 
> Without this patch, i2c reads the incorrect sgtl5000 version on a mx28evk when
> touchscreen is enabled:
>                                            
> [    5.856270] sgtl5000 0-000a: Device with ID register 0 is not a sgtl5000     
> [    9.877307] sgtl5000 0-000a: ASoC: failed to probe CODEC -19                 
> [    9.883528] mxs-sgtl5000 sound.12: ASoC: failed to instantiate card -19      
> [    9.892955] mxs-sgtl5000 sound.12: snd_soc_register_card failed (-19)  
> 
> Cc: <stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
> Signed-off-by: Fabio Estevam <fabio.estevam-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
> ---
> Applies against 3.10
> 
> Changes since v1:
> - Keep the PIO code
> 
>  drivers/i2c/busses/i2c-mxs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/busses/i2c-mxs.c b/drivers/i2c/busses/i2c-mxs.c
> index 2039f23..6d8094d 100644
> --- a/drivers/i2c/busses/i2c-mxs.c
> +++ b/drivers/i2c/busses/i2c-mxs.c
> @@ -494,7 +494,7 @@ static int mxs_i2c_xfer_msg(struct i2c_adapter *adap, struct i2c_msg *msg,
>  	 * based on this empirical measurement and a lot of previous frobbing.
>  	 */
>  	i2c->cmd_err = 0;
> -	if (msg->len < 8) {
> +	if (0) {	/* disable PIO mode until a proper fix is made */
>  		ret = mxs_i2c_pio_setup_xfer(adap, msg, flags);
>  		if (ret)
>  			mxs_i2c_reset(i2c);

I still plan to take another look at the PIO mode, but higher priority
things keep popping up in front of me. So this patch is:
Acked-by: Lucas Stach <l.stach-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
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