From: Adrian Hunter adrian.hunter@intel.com
commit f0c393e2104e48c8a881719a8bd37996f71b0aee upstream.
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 digetx@gmail.com Fixes: c07a48c2651965 ("mmc: sdhci: Remove finish_tasklet") Signed-off-by: Adrian Hunter adrian.hunter@intel.com Tested-by: Dmitry Osipenko digetx@gmail.com Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20200903082007.18715-1-adrian.hunter@intel.com Signed-off-by: Ulf Hansson ulf.hansson@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/mmc/core/sdio_ops.c | 39 ++++++++++++++++++++++----------------- 1 file changed, 22 insertions(+), 17 deletions(-)
--- a/drivers/mmc/core/sdio_ops.c +++ b/drivers/mmc/core/sdio_ops.c @@ -121,6 +121,7 @@ int mmc_io_rw_extended(struct mmc_card * 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 *
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; + + mmc_post_req(card->host, &mrq, err); + + if (nents > 1) + sg_free_table(&sgtable);
- return 0; + return err; }
int sdio_reset(struct mmc_host *host)