mmc: sdio: Use mmc_pre_req() / mmc_post_req()

SDHCI changed from using a tasklet to finish requests, to using an IRQ thread i.e. commit c07a48c2651965 ("mmc: sdhci: Remove finish_tasklet"). Because this increased the latency to complete requests, a preparatory change was made to complete the request from the IRQ handler if possible i.e. commit 19d2f695f4e827 ("mmc: sdhci: Call mmc_request_done() from IRQ handler if possible"). That alleviated the situation for MMC block devices because the MMC block driver makes use of mmc_pre_req() and mmc_post_req() so that successful requests are completed in the IRQ handler and any DMA unmapping is handled separately in mmc_post_req(). However SDIO was still affected, and an example has been reported with up to 20% degradation in performance.

Looking at SDIO I/O helper functions, sdio_io_rw_ext_helper() appeared to be a possible candidate for making use of asynchronous requests within its I/O loops, but analysis revealed that these loops almost never iterate more than once, so the complexity of the change would not be warrented.

Instead, mmc_pre_req() and mmc_post_req() are added before and after I/O submission (mmc_wait_for_req) in mmc_io_rw_extended(). This still has the potential benefit of reducing the duration of interrupt handlers, as well as addressing the latency issue for SDHCI. It also seems a more reasonable solution than forcing drivers to do everything in the IRQ handler.

Reported-by Dmitry Osipenko <[email protected]>

Fixes c07a48c2651965 ("mmc: sdhci: Remove finish_tasklet")

Signed-off-by Adrian Hunter <[email protected]>

Tested-by Dmitry Osipenko <[email protected]>

---
 drivers/mmc/core/sdio_ops.c | 39 +++++++++++++++++++++----------------
 1 file changed, 22 insertions(+), 17 deletions(-)

drivers/mmc/core/sdio_ops.c +22 -18

index 93d346c01110..4c229dd2b6e5 100644
@@ -121,6 +121,7 @@ int mmc_io_rw_extended(struct mmc_card *card, int write, unsigned fn,
        struct sg_table sgtable;
        unsigned int nents, left_size, i;
        unsigned int seg_size = card->host->max_seg_size;
+       int err;
 
        WARN_ON(blksz == 0);
 

@@ -170,28 +171,32 @@ int mmc_io_rw_extended(struct mmc_card *card, int write, unsigned fn,
 
        mmc_set_data_timeout(&data, card);
 
-       mmc_wait_for_req(card->host, &mrq);
+       mmc_pre_req(card->host, &mrq);
 
-       if (nents > 1)
-               sg_free_table(&sgtable);
+       mmc_wait_for_req(card->host, &mrq);
 
        if (cmd.error)
-               return cmd.error;
-       if (data.error)
-               return data.error;
-
-       if (mmc_host_is_spi(card->host)) {
+               err = cmd.error;
+       else if (data.error)
+               err = data.error;
+       else if (mmc_host_is_spi(card->host))
                /* host driver already reported errors */
-       } else {
-               if (cmd.resp[0] & R5_ERROR)
-                       return -EIO;
-               if (cmd.resp[0] & R5_FUNCTION_NUMBER)
-                       return -EINVAL;
-               if (cmd.resp[0] & R5_OUT_OF_RANGE)
-                       return -ERANGE;
-       }
+               err = 0;
+       else if (cmd.resp[0] & R5_ERROR)
+               err = -EIO;
+       else if (cmd.resp[0] & R5_FUNCTION_NUMBER)
+               err = -EINVAL;
+       else if (cmd.resp[0] & R5_OUT_OF_RANGE)
+               err = -ERANGE;
+       else
+               err = 0;
 
-       return 0;
+       mmc_post_req(card->host, &mrq, err);
+
+       if (nents > 1)
+               sg_free_table(&sgtable);
+
+       return err;
 }
 
 int sdio_reset(struct mmc_host *host)
--

2.17.1