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authorMarkus Pargmann <mpa@pengutronix.de>2013-10-29 08:47:47 +0100
committerVinod Koul <vinod.koul@intel.com>2013-11-13 15:38:30 +0530
commit702e94d66b555622ca6830de3095b5f0bb2ff6d7 (patch)
tree9a1319edf4ad1a6601aee57692a925e8d952bc02 /drivers/dma
parent7b11304a3c11a24a8674a47e8fd136182f86b49d (diff)
dma: mxs-dma: Fix channel reset hardware bug
This is no official errata, but I noticed that the channel reset may stop working if the DMA state engine is in the READ_FLUSH state. This patch uses the channel debug1 register to wait for the DMA statemachine to leave the READ_FLUSH state. After that we can continue to reset the channel. Tested on i.MX28. Signed-off-by: Markus Pargmann <mpa@pengutronix.de> Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Diffstat (limited to 'drivers/dma')
-rw-r--r--drivers/dma/mxs-dma.c29
1 files changed, 27 insertions, 2 deletions
diff --git a/drivers/dma/mxs-dma.c b/drivers/dma/mxs-dma.c
index 083e7f1a94f..53026706806 100644
--- a/drivers/dma/mxs-dma.c
+++ b/drivers/dma/mxs-dma.c
@@ -60,6 +60,7 @@
(((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)
+#define HW_APBX_CHn_DEBUG1(d, n) (0x150 + (n) * 0x70)
/*
* ccw bits definitions
@@ -204,12 +205,36 @@ static void mxs_dma_reset_chan(struct mxs_dma_chan *mxs_chan)
struct mxs_dma_engine *mxs_dma = mxs_chan->mxs_dma;
int chan_id = mxs_chan->chan.chan_id;
- if (dma_is_apbh(mxs_dma) && apbh_is_old(mxs_dma))
+ if (dma_is_apbh(mxs_dma) && apbh_is_old(mxs_dma)) {
writel(1 << (chan_id + BP_APBH_CTRL0_RESET_CHANNEL),
mxs_dma->base + HW_APBHX_CTRL0 + STMP_OFFSET_REG_SET);
- else
+ } else {
+ unsigned long elapsed = 0;
+ const unsigned long max_wait = 50000; /* 50ms */
+ void __iomem *reg_dbg1 = mxs_dma->base +
+ HW_APBX_CHn_DEBUG1(mxs_dma, chan_id);
+
+ /*
+ * On i.MX28 APBX, the DMA channel can stop working if we reset
+ * the channel while it is in READ_FLUSH (0x08) state.
+ * We wait here until we leave the state. Then we trigger the
+ * reset. Waiting a maximum of 50ms, the kernel shouldn't crash
+ * because of this.
+ */
+ while ((readl(reg_dbg1) & 0xf) == 0x8 && elapsed < max_wait) {
+ udelay(100);
+ elapsed += 100;
+ }
+
+ if (elapsed >= max_wait)
+ dev_err(&mxs_chan->mxs_dma->pdev->dev,
+ "Failed waiting for the DMA channel %d to leave state READ_FLUSH, trying to reset channel in READ_FLUSH state now\n",
+ chan_id);
+
+
writel(1 << (chan_id + BP_APBHX_CHANNEL_CTRL_RESET_CHANNEL),
mxs_dma->base + HW_APBHX_CHANNEL_CTRL + STMP_OFFSET_REG_SET);
+ }
}
static void mxs_dma_enable_chan(struct mxs_dma_chan *mxs_chan)