From 73a47bd0da668c99f04e9076f2b02101a5b2749b Mon Sep 17 00:00:00 2001 From: Kuninori Morimoto Date: Fri, 17 Nov 2017 02:09:32 +0000 Subject: dmaengine: rcar-dmac: use TCRB instead of TCR for residue SYS/RT/Audio DMAC includes independent data buffers for reading and writing. Therefore, the read transfer counter and write transfer counter have different values. TCR indicates read counter, and TCRB indicates write counter. The relationship is like below. TCR TCRB [SOURCE] -> [DMAC] -> [SINK] In the MEM_TO_DEV direction, what really matters is how much data has been written to the device. If the DMA is interrupted between read and write, then, the data doesn't end up in the destination, so shouldn't be counted. TCRB is thus the register we should use in this cases. In the DEV_TO_MEM direction, the situation is more complex. Both the read and write side are important. What matters from a data consumer point of view is how much data has been written to memory. On the other hand, if the transfer is interrupted between read and write, we'll end up losing data. It can also be important to report. In the MEM_TO_MEM direction, what matters is of course how much data has been written to memory from data consumer point of view. Here, because read and write have independent data buffers, it will take a while for TCR and TCRB to become equal. Thus we should check TCRB in this case, too. Thus, all cases we should check TCRB instead of TCR. Without this patch, Sound Capture has noise after PulseAudio support (= 07b7acb51d2 ("ASoC: rsnd: update pointer more accurate")), because the recorder will use wrong residue counter which indicates transferred from sound device, but in reality the data was not yet put to memory and recorder will record it. However, because DMAC is buffering data until it can be transferable size, TCRB might not be updated. For example, if consumer doesn't know how much data can be received, it requests enough size to DMAC. But in reality, it might receive very few data. In such case, DMAC just buffered it until transferable size, and no TCRB updated. In such case, this buffered data will be transferred if CHCR::DE bit was cleared, and this is happen if rcar_dmac_chan_halt(). In other word, it happen when consumer called dmaengine_terminate_all(). Because of this behavior, it need to flush buffered data when it returns "residue" (= dmaengine_tx_status()). Otherwise, consumer might calculate wrong things if it called dmaengine_tx_status() and dmaengine_terminate_all() consecutively. Signed-off-by: Kuninori Morimoto Tested-by: Hiroyuki Yokoyama Tested-by: Ryo Kodama Tested-by: Geert Uytterhoeven Signed-off-by: Vinod Koul --- drivers/dma/sh/rcar-dmac.c | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-) (limited to 'drivers/dma/sh') diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c index c99fd0f6ff13..3bbd11daa852 100644 --- a/drivers/dma/sh/rcar-dmac.c +++ b/drivers/dma/sh/rcar-dmac.c @@ -761,6 +761,23 @@ static void rcar_dmac_chcr_de_barrier(struct rcar_dmac_chan *chan) dev_err(chan->chan.device->dev, "CHCR DE check error\n"); } +static void rcar_dmac_sync_tcr(struct rcar_dmac_chan *chan) +{ + u32 chcr = rcar_dmac_chan_read(chan, RCAR_DMACHCR); + + if (!(chcr & RCAR_DMACHCR_DE)) + return; + + /* set DE=0 and flush remaining data */ + rcar_dmac_chan_write(chan, RCAR_DMACHCR, (chcr & ~RCAR_DMACHCR_DE)); + + /* make sure all remaining data was flushed */ + rcar_dmac_chcr_de_barrier(chan); + + /* back DE */ + rcar_dmac_chan_write(chan, RCAR_DMACHCR, chcr); +} + static void rcar_dmac_chan_halt(struct rcar_dmac_chan *chan) { u32 chcr = rcar_dmac_chan_read(chan, RCAR_DMACHCR); @@ -1329,8 +1346,11 @@ static unsigned int rcar_dmac_chan_get_residue(struct rcar_dmac_chan *chan, residue += chunk->size; } + if (desc->direction == DMA_DEV_TO_MEM) + rcar_dmac_sync_tcr(chan); + /* Add the residue for the current chunk. */ - residue += rcar_dmac_chan_read(chan, RCAR_DMATCR) << desc->xfer_shift; + residue += rcar_dmac_chan_read(chan, RCAR_DMATCRB) << desc->xfer_shift; return residue; } -- cgit v1.2.1