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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>
This commit is contained in:
Markus Pargmann 2013-10-29 08:47:47 +01:00 committed by Vinod Koul
parent 7b11304a3c
commit 702e94d66b
1 changed files with 27 additions and 2 deletions
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29
drivers/dma/mxs-dma.c
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@ -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)