linux-kernel - Re: [PATCH 2/2] ARM: sunxi: spi: add notice about SPI FIFO limit.

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Message-ID: <20160306181248.GV8418@lukather>
Date:	Sun, 6 Mar 2016 19:12:48 +0100
From:	Maxime Ripard <maxime.ripard@...e-electrons.com>
To:	Priit Laes <plaes@...es.org>
Cc:	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,
	Emilio López <emilio@...pez.com.ar>,
	Michal Suchanek <hramrach@...il.com>
Subject: Re: [PATCH 2/2] ARM: sunxi: spi: add notice about SPI FIFO limit.

Hi,

On Fri, Feb 26, 2016 at 07:56:57AM +0200, Priit Laes wrote:
> From: Michal Suchanek <hramrach@...il.com>
> 
> When testing SPI without DMA I noticed that filling the FIFO on the
> spi controller causes timeout. This should never happen with DMA support
> so just adding a comment.
> 
> Signed-off-by: Michal Suchanek <hramrach@...il.com>
> ---
>  drivers/spi/spi-sun4i.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/spi/spi-sun4i.c b/drivers/spi/spi-sun4i.c
> index 78141a6..b750664 100644
> --- a/drivers/spi/spi-sun4i.c
> +++ b/drivers/spi/spi-sun4i.c
> @@ -333,7 +333,9 @@ static int sun4i_spi_transfer_one(struct spi_master *master,
>  		sun4i_spi_write(sspi, SUN4I_DMA_CTL_REG, 0);
>  
>  		/* 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 */
> +		/* The can_dma check is txlen >= SUN4I_FIFO_DEPTH so with DMA this should never happen anyway. */
> +		sun4i_spi_fill_fifo(sspi, SUN4I_FIFO_DEPTH - 1);

Please wrap the lines at 80 chars and use the proper multiline comment
style.

Thanks!
Maxime

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

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