From mboxrd@z Thu Jan  1 00:00:00 1970
From: vinod.koul@intel.com (Vinod Koul)
Date: Wed, 13 Nov 2013 15:32:42 +0530
Subject: [PATCH v5 2/5] dma: mxs-dma: Report correct residue for cyclic DMA
In-Reply-To: <1383032869-12863-3-git-send-email-mpa@pengutronix.de>
References: <1383032869-12863-1-git-send-email-mpa@pengutronix.de>
 <1383032869-12863-3-git-send-email-mpa@pengutronix.de>
Message-ID: <20131113100242.GU8834@intel.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Tue, Oct 29, 2013 at 08:47:46AM +0100, Markus Pargmann wrote:
> Use the channel's buffer address register to calculate correct residue
> value for tx_status.
> 
> Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
> ---
>  drivers/dma/mxs-dma.c | 20 +++++++++++++++++++-
>  1 file changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/dma/mxs-dma.c b/drivers/dma/mxs-dma.c
> index 1d1b6e9..083e7f1 100644
> --- a/drivers/dma/mxs-dma.c
> +++ b/drivers/dma/mxs-dma.c
> @@ -58,6 +58,8 @@
>  	(((dma_is_apbh(d) && apbh_is_old(d)) ? 0x050 : 0x110) + (n) * 0x70)
>  #define HW_APBHX_CHn_SEMA(d, n) \
>  	(((dma_is_apbh(d) && apbh_is_old(d)) ? 0x080 : 0x140) + (n) * 0x70)
> +#define HW_APBHX_CHn_BAR(d, n) \
> +	(((dma_is_apbh(d) && apbh_is_old(d)) ? 0x070 : 0x130) + (n) * 0x70)
>  
>  /*
>   * ccw bits definitions
> @@ -623,8 +625,24 @@ static enum dma_status mxs_dma_tx_status(struct dma_chan *chan,
>  			dma_cookie_t cookie, struct dma_tx_state *txstate)
>  {
>  	struct mxs_dma_chan *mxs_chan = to_mxs_dma_chan(chan);
> +	struct mxs_dma_engine *mxs_dma = mxs_chan->mxs_dma;
> +	u32 residue = 0;
> +
> +	if (mxs_chan->status == DMA_IN_PROGRESS &&
> +			mxs_chan->flags & MXS_DMA_SG_LOOP) {
> +		struct mxs_dma_ccw *last_ccw;
> +		u32 bar;
> +
> +		last_ccw = &mxs_chan->ccw[mxs_chan->desc_count - 1];
> +		residue = last_ccw->xfer_bytes + last_ccw->bufaddr;
> +
> +		bar = readl(mxs_dma->base +
> +				HW_APBHX_CHn_BAR(mxs_dma, chan->chan_id));
> +		residue -= bar;
> +	}
>  
> -	dma_set_tx_state(txstate, chan->completed_cookie, chan->cookie, 0);
> +	dma_set_tx_state(txstate, chan->completed_cookie, chan->cookie,
> +			residue);
>  
>  	return mxs_chan->status;
This will work for your driver where we have artficial restriction on allowing
only 1 descriptor to be submitted at any point of time. I winder what made that
restriction?

--
~Vinod