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Message-ID: <C246CAC1457055469EF09E3A7AC4E11A4A65C899@XAP-PVEXMBX01.xlnx.xilinx.com>
Date: Thu, 15 Dec 2016 15:19:58 +0000
From: Appana Durga Kedareswara Rao <appana.durga.rao@...inx.com>
To: Jose Abreu <Jose.Abreu@...opsys.com>,
"dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>
CC: Carlos Palminha <CARLOS.PALMINHA@...opsys.com>,
Vinod Koul <vinod.koul@...el.com>,
Dan Williams <dan.j.williams@...el.com>,
"Laurent Pinchart" <laurent.pinchart@...asonboard.com>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] dmaengine: xilinx_dma: Add support for multiple buffers
Hi Jose Abreu,
Thanks for the patch...
>
> Xilinx VDMA supports multiple framebuffers. This patch adds correct handling for
> the scenario where multiple framebuffers are available in the HW and parking
> mode is not set.
>
> We corrected these situations:
> 1) Do not start VDMA until all the framebuffers
> have been programmed with a valid address.
> 2) Restart variables when VDMA halts/resets.
> 3) Halt channel when all the framebuffers have
> finished and there is not anymore segments
> pending.
> 4) Do not try to overlap framebuffers until they
> are completed.
>
> All these situations, without this patch, can lead to data corruption and even
> system memory corruption. If, for example, user has a VDMA with 3
> framebuffers, with direction DMA_DEV_TO_MEM and user only submits one
> segment, VDMA will write first to the segment the user submitted BUT if the
> user doesn't submit another segment in a timelly manner then VDMA will write
> to position 0 of system mem in the following VSYNC.
I have posted different patch series for fixing these issues just now...
Please take a look into it...
Regards,
Kedar.
>
> Signed-off-by: Jose Abreu <joabreu@...opsys.com>
> Cc: Carlos Palminha <palminha@...opsys.com>
> Cc: Vinod Koul <vinod.koul@...el.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Kedareswara rao Appana <appana.durga.rao@...inx.com>
> Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> Cc: dmaengine@...r.kernel.org
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-kernel@...r.kernel.org
> ---
> drivers/dma/xilinx/xilinx_dma.c | 80 ++++++++++++++++++++++++++++++++++-
> ------
> 1 file changed, 68 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c
> index 8288fe4..30eec5a 100644
> --- a/drivers/dma/xilinx/xilinx_dma.c
> +++ b/drivers/dma/xilinx/xilinx_dma.c
> @@ -351,10 +351,12 @@ struct xilinx_dma_chan {
> bool cyclic;
> bool genlock;
> bool err;
> + bool running;
> struct tasklet_struct tasklet;
> struct xilinx_vdma_config config;
> bool flush_on_fsync;
> u32 desc_pendingcount;
> + u32 seg_pendingcount;
> bool ext_addr;
> u32 desc_submitcount;
> u32 residue;
> @@ -946,6 +948,17 @@ static bool xilinx_dma_is_idle(struct xilinx_dma_chan
> *chan) }
>
> /**
> + * xilinx_vdma_is_multi_buffer - Check if VDMA has multiple
> +framebuffers
> + * @chan: Driver specific DMA channel
> + *
> + * Return: '1' if is multi buffer, '0' if not.
> + */
> +static bool xilinx_vdma_is_multi_buffer(struct xilinx_dma_chan *chan) {
> + return chan->num_frms > 1;
> +}
> +
> +/**
> * xilinx_dma_halt - Halt DMA channel
> * @chan: Driver specific DMA channel
> */
> @@ -966,6 +979,10 @@ static void xilinx_dma_halt(struct xilinx_dma_chan
> *chan)
> chan, dma_ctrl_read(chan,
> XILINX_DMA_REG_DMASR));
> chan->err = true;
> }
> +
> + chan->seg_pendingcount = 0;
> + chan->desc_submitcount = 0;
> + chan->running = false;
> }
>
> /**
> @@ -1002,14 +1019,35 @@ static void xilinx_vdma_start_transfer(struct
> xilinx_dma_chan *chan)
> struct xilinx_dma_tx_descriptor *desc, *tail_desc;
> u32 reg;
> struct xilinx_vdma_tx_segment *tail_segment;
> + bool mbf = xilinx_vdma_is_multi_buffer(chan) && !config->park;
>
> /* This function was invoked with lock held */
> if (chan->err)
> return;
>
> - if (list_empty(&chan->pending_list))
> + /*
> + * Can't continue if we have already consumed all the available
> + * framebuffers and they are not done yet.
> + */
> + if (mbf && (chan->seg_pendingcount >= chan->num_frms))
> return;
>
> + if (list_empty(&chan->pending_list)) {
> + /*
> + * Can't keep running if there are no pending segments. Halt
> + * the channel as security measure. Notice that this will not
> + * corrupt current transactions because this function is
> + * called after the pendingcount is decreased and after the
> + * current transaction has finished.
> + */
> + if (mbf && chan->running && !chan->seg_pendingcount) {
> + dev_dbg(chan->dev, "pending list empty: halting\n");
> + xilinx_dma_halt(chan);
> + }
> +
> + return;
> + }
> +
> desc = list_first_entry(&chan->pending_list,
> struct xilinx_dma_tx_descriptor, node);
> tail_desc = list_last_entry(&chan->pending_list,
> @@ -1079,6 +1117,8 @@ static void xilinx_vdma_start_transfer(struct
> xilinx_dma_chan *chan)
> if (chan->has_sg) {
> dma_ctrl_write(chan, XILINX_DMA_REG_TAILDESC,
> tail_segment->phys);
> + list_splice_tail_init(&chan->pending_list, &chan->active_list);
> + chan->desc_pendingcount = 0;
> } else {
> struct xilinx_vdma_tx_segment *segment, *last = NULL;
> int i = 0;
> @@ -1097,29 +1137,34 @@ static void xilinx_vdma_start_transfer(struct
> xilinx_dma_chan *chan)
>
> XILINX_VDMA_REG_START_ADDRESS(i++),
> segment->hw.buf_addr);
>
> + chan->seg_pendingcount++;
> last = segment;
> }
>
> if (!last)
> return;
>
> - /* HW expects these parameters to be same for one
> transaction */
> - vdma_desc_write(chan, XILINX_DMA_REG_HSIZE, last-
> >hw.hsize);
> - vdma_desc_write(chan, XILINX_DMA_REG_FRMDLY_STRIDE,
> - last->hw.stride);
> - vdma_desc_write(chan, XILINX_DMA_REG_VSIZE, last-
> >hw.vsize);
> - }
> -
> - if (!chan->has_sg) {
> list_del(&desc->node);
> list_add_tail(&desc->node, &chan->active_list);
> chan->desc_submitcount++;
> chan->desc_pendingcount--;
> if (chan->desc_submitcount == chan->num_frms)
> chan->desc_submitcount = 0;
> - } else {
> - list_splice_tail_init(&chan->pending_list, &chan->active_list);
> - chan->desc_pendingcount = 0;
> +
> + /*
> + * Can't start until all the framebuffers have been programmed
> + * or else corruption can occur.
> + */
> + if (mbf && !chan->running &&
> + (chan->seg_pendingcount < chan->num_frms))
> + return;
> +
> + /* HW expects these parameters to be same for one
> transaction */
> + vdma_desc_write(chan, XILINX_DMA_REG_HSIZE, last-
> >hw.hsize);
> + vdma_desc_write(chan, XILINX_DMA_REG_FRMDLY_STRIDE,
> + last->hw.stride);
> + vdma_desc_write(chan, XILINX_DMA_REG_VSIZE, last-
> >hw.vsize);
> + chan->running = true;
> }
> }
>
> @@ -1327,12 +1372,20 @@ static void xilinx_dma_issue_pending(struct
> dma_chan *dchan) static void xilinx_dma_complete_descriptor(struct
> xilinx_dma_chan *chan) {
> struct xilinx_dma_tx_descriptor *desc, *next;
> + struct xilinx_vdma_tx_segment *segment;
>
> /* This function was invoked with lock held */
> if (list_empty(&chan->active_list))
> return;
>
> list_for_each_entry_safe(desc, next, &chan->active_list, node) {
> + if (chan->xdev->dma_config->dmatype == XDMA_TYPE_VDMA)
> {
> + list_for_each_entry(segment, &desc->segments, node)
> {
> + if (chan->seg_pendingcount > 0)
> + chan->seg_pendingcount--;
> + }
> + }
> +
> list_del(&desc->node);
> if (!desc->cyclic)
> dma_cookie_complete(&desc->async_tx);
> @@ -1366,6 +1419,9 @@ static int xilinx_dma_reset(struct xilinx_dma_chan
> *chan)
> }
>
> chan->err = false;
> + chan->seg_pendingcount = 0;
> + chan->desc_submitcount = 0;
> + chan->running = false;
>
> return err;
> }
> --
> 1.9.1
>
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