This is a note to let you know that I've just added the patch titled
dmaengine: xilinx: xdma: Fix synchronization issue
to the 6.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
dmaengine-xilinx-xdma-fix-synchronization-issue.patch
and it can be found in the queue-6.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 6a40fb8245965b481b4dcce011cd63f20bf91ee0 Mon Sep 17 00:00:00 2001
From: Louis Chauvet <louis.chauvet@xxxxxxxxxxx>
Date: Wed, 27 Mar 2024 10:58:49 +0100
Subject: dmaengine: xilinx: xdma: Fix synchronization issue
From: Louis Chauvet <louis.chauvet@xxxxxxxxxxx>
commit 6a40fb8245965b481b4dcce011cd63f20bf91ee0 upstream.
The current xdma_synchronize method does not properly wait for the last
transfer to be done. Due to limitations of the XMDA engine, it is not
possible to stop a transfer in the middle of a descriptor. Said
otherwise, if a stop is requested at the end of descriptor "N" and the OS
is fast enough, the DMA controller will effectively stop immediately.
However, if the OS is slightly too slow to request the stop and the DMA
engine starts descriptor "N+1", the N+1 transfer will be performed until
its end. This means that after a terminate_all, the last descriptor must
remain valid and the synchronization must wait for this last descriptor to
be terminated.
Fixes: 855c2e1d1842 ("dmaengine: xilinx: xdma: Rework xdma_terminate_all()")
Fixes: f5c392d106e7 ("dmaengine: xilinx: xdma: Add terminate_all/synchronize callbacks")
Cc: stable@xxxxxxxxxxxxxxx
Suggested-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
Signed-off-by: Louis Chauvet <louis.chauvet@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240327-digigram-xdma-fixes-v1-2-45f4a52c0283@xxxxxxxxxxx
Signed-off-by: Vinod Koul <vkoul@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/dma/xilinx/xdma-regs.h | 3 +++
drivers/dma/xilinx/xdma.c | 26 ++++++++++++++++++--------
2 files changed, 21 insertions(+), 8 deletions(-)
--- a/drivers/dma/xilinx/xdma-regs.h
+++ b/drivers/dma/xilinx/xdma-regs.h
@@ -117,6 +117,9 @@ struct xdma_hw_desc {
CHAN_CTRL_IE_WRITE_ERROR | \
CHAN_CTRL_IE_DESC_ERROR)
+/* bits of the channel status register */
+#define XDMA_CHAN_STATUS_BUSY BIT(0)
+
#define XDMA_CHAN_STATUS_MASK CHAN_CTRL_START
#define XDMA_CHAN_ERROR_MASK (CHAN_CTRL_IE_DESC_ALIGN_MISMATCH | \
--- a/drivers/dma/xilinx/xdma.c
+++ b/drivers/dma/xilinx/xdma.c
@@ -71,6 +71,8 @@ struct xdma_chan {
enum dma_transfer_direction dir;
struct dma_slave_config cfg;
u32 irq;
+ struct completion last_interrupt;
+ bool stop_requested;
};
/**
@@ -376,6 +378,8 @@ static int xdma_xfer_start(struct xdma_c
return ret;
xchan->busy = true;
+ xchan->stop_requested = false;
+ reinit_completion(&xchan->last_interrupt);
return 0;
}
@@ -387,7 +391,6 @@ static int xdma_xfer_start(struct xdma_c
static int xdma_xfer_stop(struct xdma_chan *xchan)
{
int ret;
- u32 val;
struct xdma_device *xdev = xchan->xdev_hdl;
/* clear run stop bit to prevent any further auto-triggering */
@@ -395,13 +398,7 @@ static int xdma_xfer_stop(struct xdma_ch
CHAN_CTRL_RUN_STOP);
if (ret)
return ret;
-
- /* Clear the channel status register */
- ret = regmap_read(xdev->rmap, xchan->base + XDMA_CHAN_STATUS_RC, &val);
- if (ret)
- return ret;
-
- return 0;
+ return ret;
}
/**
@@ -474,6 +471,8 @@ static int xdma_alloc_channels(struct xd
xchan->xdev_hdl = xdev;
xchan->base = base + i * XDMA_CHAN_STRIDE;
xchan->dir = dir;
+ xchan->stop_requested = false;
+ init_completion(&xchan->last_interrupt);
ret = xdma_channel_init(xchan);
if (ret)
@@ -521,6 +520,7 @@ static int xdma_terminate_all(struct dma
spin_lock_irqsave(&xdma_chan->vchan.lock, flags);
xdma_chan->busy = false;
+ xdma_chan->stop_requested = true;
vd = vchan_next_desc(&xdma_chan->vchan);
if (vd) {
list_del(&vd->node);
@@ -542,6 +542,13 @@ static int xdma_terminate_all(struct dma
static void xdma_synchronize(struct dma_chan *chan)
{
struct xdma_chan *xdma_chan = to_xdma_chan(chan);
+ struct xdma_device *xdev = xdma_chan->xdev_hdl;
+ int st = 0;
+
+ /* If the engine continues running, wait for the last interrupt */
+ regmap_read(xdev->rmap, xdma_chan->base + XDMA_CHAN_STATUS, &st);
+ if (st & XDMA_CHAN_STATUS_BUSY)
+ wait_for_completion_timeout(&xdma_chan->last_interrupt, msecs_to_jiffies(1000));
vchan_synchronize(&xdma_chan->vchan);
}
@@ -876,6 +883,9 @@ static irqreturn_t xdma_channel_isr(int
u32 st;
bool repeat_tx;
+ if (xchan->stop_requested)
+ complete(&xchan->last_interrupt);
+
spin_lock(&xchan->vchan.lock);
/* get submitted request */
Patches currently in stable-queue which might be from louis.chauvet@xxxxxxxxxxx are
queue-6.8/dmaengine-xilinx-xdma-fix-synchronization-issue.patch
queue-6.8/dmaengine-xilinx-xdma-fix-wrong-offsets-in-the-buffers-addresses-in-dma-descriptor.patch
