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Subject[PATCH v7 2/6] dmaeninge: xilinx_dma: Fix bug in multiple frame stores scenario in vdma
Date
VDMA engine default frame buffer configuration is cirular mode.
in this mode dmaengine continuously circles through h/w configured fstore
frame buffers.

When vdma h/w is configured for more than one frame.
for example h/w is configured for n number of frames, user
submits less than n number of frames and triggered the dmaengine
using issue_pending API.

since the h/w (or) driver default configuraiton is circular mode
h/w tries to write/read from an invalid frame buffer resulting
errors from the vdma dmaengine.

This patch fixes this issue by enabling the park mode as
default mode configuration for frame buffers in s/w,
so that driver can handle all cases for "k" frames where n%k==0
(n is a multiple of k) by simply replicating the frame pointers.

Signed-off-by: Kedareswara rao Appana <appanad@xilinx.com>
---
Changes for v7:
---> Used park mode as default configuration as suggested
by Mike Looijmans.
---> Updated commit message as suggested by Vinod(No need to
start each line with Title cases).
Changes for v6:
---> Added Rob Acked-by
---> Updated commit message as suggested by Vinod.
Changes for v5:
---> Updated xlnx,fstore-config property to xlnx,fstore-enable
and updated description as suggested by Rob.
Changes for v4:
---> Add Check for framestore configuration on Transmit case as well
as suggested by Jose Abreu.
---> Modified the dev_dbg checks to dev_warn checks as suggested
by Jose Abreu.
Changes for v3:
---> Added Checks for frame store configuration. If frame store
Configuration is not present at the h/w level and user
Submits less frames added debug prints in the driver as relevant.
Changes for v2:
---> Fixed race conditions in the driver as suggested by Jose Abreu
---> Fixed unnecessray if else checks in the vdma_start_transfer
as suggested by Laurent Pinchart.

drivers/dma/xilinx/xilinx_dma.c | 41 +++++++++++++++++++----------------------
1 file changed, 19 insertions(+), 22 deletions(-)

diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c
index c246563..9063ca0 100644
--- a/drivers/dma/xilinx/xilinx_dma.c
+++ b/drivers/dma/xilinx/xilinx_dma.c
@@ -99,7 +99,9 @@
#define XILINX_DMA_REG_FRMPTR_STS 0x0024
#define XILINX_DMA_REG_PARK_PTR 0x0028
#define XILINX_DMA_PARK_PTR_WR_REF_SHIFT 8
+#define XILINX_DMA_PARK_PTR_WR_REF_MASK GENMASK(12, 8)
#define XILINX_DMA_PARK_PTR_RD_REF_SHIFT 0
+#define XILINX_DMA_PARK_PTR_RD_REF_MASK GENMASK(4, 0)
#define XILINX_DMA_REG_VDMA_VERSION 0x002c

/* Register Direct Mode Registers */
@@ -998,7 +1000,7 @@ static void xilinx_vdma_start_transfer(struct xilinx_dma_chan *chan)
{
struct xilinx_vdma_config *config = &chan->config;
struct xilinx_dma_tx_descriptor *desc, *tail_desc;
- u32 reg;
+ u32 reg, j;
struct xilinx_vdma_tx_segment *tail_segment;

/* This function was invoked with lock held */
@@ -1035,10 +1037,6 @@ static void xilinx_vdma_start_transfer(struct xilinx_dma_chan *chan)
else
reg &= ~XILINX_DMA_DMACR_FRAMECNT_EN;

- /* Configure channel to allow number frame buffers */
- dma_ctrl_write(chan, XILINX_DMA_REG_FRMSTORE,
- chan->desc_pendingcount);
-
/*
* With SG, start with circular mode, so that BDs can be fetched.
* In direct register mode, if not parking, enable circular mode
@@ -1051,17 +1049,16 @@ static void xilinx_vdma_start_transfer(struct xilinx_dma_chan *chan)

dma_ctrl_write(chan, XILINX_DMA_REG_DMACR, reg);

- if (config->park && (config->park_frm >= 0) &&
- (config->park_frm < chan->num_frms)) {
- if (chan->direction == DMA_MEM_TO_DEV)
- dma_write(chan, XILINX_DMA_REG_PARK_PTR,
- config->park_frm <<
- XILINX_DMA_PARK_PTR_RD_REF_SHIFT);
- else
- dma_write(chan, XILINX_DMA_REG_PARK_PTR,
- config->park_frm <<
- XILINX_DMA_PARK_PTR_WR_REF_SHIFT);
+ j = chan->desc_submitcount;
+ reg = dma_read(chan, XILINX_DMA_REG_PARK_PTR);
+ if (chan->direction == DMA_MEM_TO_DEV) {
+ reg &= ~XILINX_DMA_PARK_PTR_RD_REF_MASK;
+ reg |= j << XILINX_DMA_PARK_PTR_RD_REF_SHIFT;
+ } else {
+ reg &= ~XILINX_DMA_PARK_PTR_WR_REF_MASK;
+ reg |= j << XILINX_DMA_PARK_PTR_WR_REF_SHIFT;
}
+ dma_write(chan, XILINX_DMA_REG_PARK_PTR, reg);

/* Start the hardware */
xilinx_dma_start(chan);
@@ -1073,6 +1070,8 @@ 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;
@@ -1102,18 +1101,13 @@ static void xilinx_vdma_start_transfer(struct xilinx_dma_chan *chan)
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--;
+ list_del(&desc->node);
+ list_add_tail(&desc->node, &chan->active_list);
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;
}

chan->idle = false;
@@ -1364,6 +1358,7 @@ static int xilinx_dma_reset(struct xilinx_dma_chan *chan)

chan->err = false;
chan->idle = true;
+ chan->desc_submitcount = 0;

return err;
}
@@ -2363,6 +2358,7 @@ static int xilinx_dma_chan_probe(struct xilinx_dma_device *xdev,
chan->ctrl_offset = XILINX_DMA_MM2S_CTRL_OFFSET;
if (xdev->dma_config->dmatype == XDMA_TYPE_VDMA) {
chan->desc_offset = XILINX_VDMA_MM2S_DESC_OFFSET;
+ chan->config.park = 1;

if (xdev->flush_on_fsync == XILINX_DMA_FLUSH_BOTH ||
xdev->flush_on_fsync == XILINX_DMA_FLUSH_MM2S)
@@ -2379,6 +2375,7 @@ static int xilinx_dma_chan_probe(struct xilinx_dma_device *xdev,
chan->ctrl_offset = XILINX_DMA_S2MM_CTRL_OFFSET;
if (xdev->dma_config->dmatype == XDMA_TYPE_VDMA) {
chan->desc_offset = XILINX_VDMA_S2MM_DESC_OFFSET;
+ chan->config.park = 1;

if (xdev->flush_on_fsync == XILINX_DMA_FLUSH_BOTH ||
xdev->flush_on_fsync == XILINX_DMA_FLUSH_S2MM)
--
2.7.4
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