mmc: tmio_mmc: fix PIO fallback on DMA descriptor allocation failure

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>

diff --git a/drivers/mmc/host/tmio_mmc.c b/drivers/mmc/host/tmio_mmc.c
index 4e75799..63115a6 100644 (file)
--- a/drivers/mmc/host/tmio_mmc.c
+++ b/drivers/mmc/host/tmio_mmc.c
@@ -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);
@@ -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;
@@ -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);
@@ -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;
@@ -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)
@@ -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;
@@ -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,
@@ -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 */

diff --git a/drivers/mmc/host/tmio_mmc.h b/drivers/mmc/host/tmio_mmc.h
index 0fedc78..0b7d916 100644 (file)
--- a/drivers/mmc/host/tmio_mmc.h
+++ b/drivers/mmc/host/tmio_mmc.h
@@ -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
 };