linux-kernel - Re: [PATCH 2/5] spi: sun4i: fix FIFO limit

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Date:	Mon, 30 May 2016 10:37:00 +0200
From:	Maxime Ripard <maxime.ripard@...e-electrons.com>
To:	Michal Suchanek <hramrach@...il.com>
Cc:	linux-sunxi@...glegroups.com, Mark Brown <broonie@...nel.org>,
	Chen-Yu Tsai <wens@...e.org>, linux-spi@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] spi: sun4i: fix FIFO limit

Hi,

On Thu, May 26, 2016 at 07:25:24PM -0000, Michal Suchanek wrote:
> When testing SPI without DMA I noticed that filling the FIFO on the
> spi controller causes timeout.
> 
> Always leave room for one byte in the FIFO.
> 
> Signed-off-by: Michal Suchanek <hramrach@...il.com>

Sending it to stable would be great (with a fixes tag too).

> 
> ---
> v2:
> use EMSGSIZE instead of EINVAL
> ---
>  drivers/spi/spi-sun4i.c | 8 ++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/spi/spi-sun4i.c b/drivers/spi/spi-sun4i.c
> index fe63bbd..04f1b77 100644
> --- a/drivers/spi/spi-sun4i.c
> +++ b/drivers/spi/spi-sun4i.c
> @@ -180,7 +180,9 @@ static int sun4i_spi_transfer_one(struct spi_master *master,
>  
>  	/* We don't support transfer larger than the FIFO */
>  	if (tfr->len > SUN4I_FIFO_DEPTH)
> -		return -EINVAL;
> +		return -EMSGSIZE;

One new line here.

> +	if (tfr->tx_buf && tfr->len >= SUN4I_FIFO_DEPTH)
> +		return -EMSGSIZE;
>  
>  	reinit_completion(&sspi->done);
>  	sspi->tx_buf = tfr->tx_buf;
> @@ -271,7 +273,9 @@ static int sun4i_spi_transfer_one(struct spi_master *master,
>  	sun4i_spi_write(sspi, SUN4I_XMIT_CNT_REG, SUN4I_XMIT_CNT(tx_len));
>  
>  	/* Fill the TX FIFO */
> -	sun4i_spi_fill_fifo(sspi, SUN4I_FIFO_DEPTH);
> +	/* Filling the FIFO fully causes timeout for some reason
> +	 * at least on spi2 on A10s */

This is not the proper comment style and generate a warning with
checkpatch, please fix that (and merge the comment with the previous
comment).

Thanks!
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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