diff options
| author | Markus Pargmann <mpa@pengutronix.de> | 2013-10-29 08:47:47 +0100 |
|---|---|---|
| committer | Vinod Koul <vinod.koul@intel.com> | 2013-11-13 15:38:30 +0530 |
| commit | 702e94d66b555622ca6830de3095b5f0bb2ff6d7 (patch) | |
| tree | 9a1319edf4ad1a6601aee57692a925e8d952bc02 /drivers/dma/mxs-dma.c | |
| parent | 7b11304a3c11a24a8674a47e8fd136182f86b49d (diff) | |
| download | linux-702e94d66b555622ca6830de3095b5f0bb2ff6d7.tar.gz linux-702e94d66b555622ca6830de3095b5f0bb2ff6d7.tar.bz2 linux-702e94d66b555622ca6830de3095b5f0bb2ff6d7.zip | |
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/mxs-dma.c')
| -rw-r--r-- | drivers/dma/mxs-dma.c | 29 |
1 files changed, 27 insertions, 2 deletions
diff --git a/drivers/dma/mxs-dma.c b/drivers/dma/mxs-dma.c index 083e7f1a94f0..530267068061 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) |