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mmc: tmio_mmc: fix PIO fallback on DMA descriptor allocation failure
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The easiest way to fall back to PIO, when a DMA descriptor allocation
fails is to disable DMA on the controller but continue with the current
request in PIO mode. This way tmio_mmc_start_dma() can become void, since
it cannot be failing any more. The current version is also broken: it is
testing a wrong pointer and thus failing to recognise, that a descriptor
allocation wasn't successful.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Chris Ball <cjb@laptop.org>
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Guennadi Liakhovetski authored and Chris Ball committed Jan 9, 2011
1 parent 729b0c7 commit ef17fee
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Showing 2 changed files with 25 additions and 46 deletions.
69 changes: 25 additions & 44 deletions drivers/mmc/host/tmio_mmc.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -427,11 +427,12 @@ static void tmio_dma_complete(void *arg)
enable_mmc_irqs(host, TMIO_STAT_DATAEND);
}

static int tmio_mmc_start_dma_rx(struct tmio_mmc_host *host)
static void tmio_mmc_start_dma_rx(struct tmio_mmc_host *host)
{
struct scatterlist *sg = host->sg_ptr;
struct dma_async_tx_descriptor *desc = NULL;
struct dma_chan *chan = host->chan_rx;
dma_cookie_t cookie;
int ret;

ret = dma_map_sg(&host->pdev->dev, sg, host->sg_len, DMA_FROM_DEVICE);
Expand All @@ -442,21 +443,20 @@ static int tmio_mmc_start_dma_rx(struct tmio_mmc_host *host)
}

if (desc) {
host->desc = desc;
desc->callback = tmio_dma_complete;
desc->callback_param = host;
host->cookie = desc->tx_submit(desc);
if (host->cookie < 0) {
host->desc = NULL;
ret = host->cookie;
cookie = desc->tx_submit(desc);
if (cookie < 0) {
desc = NULL;
ret = cookie;
} else {
chan->device->device_issue_pending(chan);
}
}
dev_dbg(&host->pdev->dev, "%s(): mapped %d -> %d, cookie %d, rq %p\n",
__func__, host->sg_len, ret, host->cookie, host->mrq);
__func__, host->sg_len, ret, cookie, host->mrq);

if (!host->desc) {
if (!desc) {
/* DMA failed, fall back to PIO */
if (ret >= 0)
ret = -EIO;
Expand All @@ -471,23 +471,18 @@ static int tmio_mmc_start_dma_rx(struct tmio_mmc_host *host)
dev_warn(&host->pdev->dev,
"DMA failed: %d, falling back to PIO\n", ret);
tmio_mmc_enable_dma(host, false);
reset(host);
/* Fail this request, let above layers recover */
host->mrq->cmd->error = ret;
tmio_mmc_finish_request(host);
}

dev_dbg(&host->pdev->dev, "%s(): desc %p, cookie %d, sg[%d]\n", __func__,
desc, host->cookie, host->sg_len);

return ret > 0 ? 0 : ret;
desc, cookie, host->sg_len);
}

static int tmio_mmc_start_dma_tx(struct tmio_mmc_host *host)
static void tmio_mmc_start_dma_tx(struct tmio_mmc_host *host)
{
struct scatterlist *sg = host->sg_ptr;
struct dma_async_tx_descriptor *desc = NULL;
struct dma_chan *chan = host->chan_tx;
dma_cookie_t cookie;
int ret;

ret = dma_map_sg(&host->pdev->dev, sg, host->sg_len, DMA_TO_DEVICE);
Expand All @@ -498,19 +493,18 @@ static int tmio_mmc_start_dma_tx(struct tmio_mmc_host *host)
}

if (desc) {
host->desc = desc;
desc->callback = tmio_dma_complete;
desc->callback_param = host;
host->cookie = desc->tx_submit(desc);
if (host->cookie < 0) {
host->desc = NULL;
ret = host->cookie;
cookie = desc->tx_submit(desc);
if (cookie < 0) {
desc = NULL;
ret = cookie;
}
}
dev_dbg(&host->pdev->dev, "%s(): mapped %d -> %d, cookie %d, rq %p\n",
__func__, host->sg_len, ret, host->cookie, host->mrq);
__func__, host->sg_len, ret, cookie, host->mrq);

if (!host->desc) {
if (!desc) {
/* DMA failed, fall back to PIO */
if (ret >= 0)
ret = -EIO;
Expand All @@ -525,30 +519,22 @@ static int tmio_mmc_start_dma_tx(struct tmio_mmc_host *host)
dev_warn(&host->pdev->dev,
"DMA failed: %d, falling back to PIO\n", ret);
tmio_mmc_enable_dma(host, false);
reset(host);
/* Fail this request, let above layers recover */
host->mrq->cmd->error = ret;
tmio_mmc_finish_request(host);
}

dev_dbg(&host->pdev->dev, "%s(): desc %p, cookie %d\n", __func__,
desc, host->cookie);

return ret > 0 ? 0 : ret;
desc, cookie);
}

static int tmio_mmc_start_dma(struct tmio_mmc_host *host,
static void tmio_mmc_start_dma(struct tmio_mmc_host *host,
struct mmc_data *data)
{
if (data->flags & MMC_DATA_READ) {
if (host->chan_rx)
return tmio_mmc_start_dma_rx(host);
tmio_mmc_start_dma_rx(host);
} else {
if (host->chan_tx)
return tmio_mmc_start_dma_tx(host);
tmio_mmc_start_dma_tx(host);
}

return 0;
}

static void tmio_issue_tasklet_fn(unsigned long priv)
Expand Down Expand Up @@ -584,9 +570,6 @@ static bool tmio_mmc_filter(struct dma_chan *chan, void *arg)
static void tmio_mmc_request_dma(struct tmio_mmc_host *host,
struct tmio_mmc_data *pdata)
{
host->cookie = -EINVAL;
host->desc = NULL;

/* We can only either use DMA for both Tx and Rx or not use it at all */
if (pdata->dma) {
dma_cap_mask_t mask;
Expand Down Expand Up @@ -632,15 +615,11 @@ static void tmio_mmc_release_dma(struct tmio_mmc_host *host)
host->chan_rx = NULL;
dma_release_channel(chan);
}

host->cookie = -EINVAL;
host->desc = NULL;
}
#else
static int tmio_mmc_start_dma(struct tmio_mmc_host *host,
static void tmio_mmc_start_dma(struct tmio_mmc_host *host,
struct mmc_data *data)
{
return 0;
}

static void tmio_mmc_request_dma(struct tmio_mmc_host *host,
Expand Down Expand Up @@ -682,7 +661,9 @@ static int tmio_mmc_start_data(struct tmio_mmc_host *host,
sd_ctrl_write16(host, CTL_SD_XFER_LEN, data->blksz);
sd_ctrl_write16(host, CTL_XFER_BLK_COUNT, data->blocks);

return tmio_mmc_start_dma(host, data);
tmio_mmc_start_dma(host, data);

return 0;
}

/* Process requests from the MMC layer */
Expand Down
2 changes: 0 additions & 2 deletions drivers/mmc/host/tmio_mmc.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -112,9 +112,7 @@ struct tmio_mmc_host {
struct tasklet_struct dma_complete;
struct tasklet_struct dma_issue;
#ifdef CONFIG_TMIO_MMC_DMA
struct dma_async_tx_descriptor *desc;
unsigned int dma_sglen;
dma_cookie_t cookie;
#endif
};

Expand Down

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