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From patchwork Thu Sep 3 08:20:07 2020
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X-Patchwork-Submitter: Adrian Hunter <adrian.hunter@intel.com>
X-Patchwork-Id: 11752795
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From: Adrian Hunter <adrian.hunter@intel.com>
To: Ulf Hansson <ulf.hansson@linaro.org>
Cc: linux-mmc <linux-mmc@vger.kernel.org>,
=?utf-8?q?Pali_Roh=C3=A1r?= <pali@kernel.org>,
Haibo Chen <haibo.chen@nxp.com>, Yue Hu <huyue2@yulong.com>,
Douglas Anderson <dianders@chromium.org>, Dmitry Osipenko <digetx@gmail.com>
Subject: [PATCH] mmc: sdio: Use mmc_pre_req() / mmc_post_req()
Date: Thu, 3 Sep 2020 11:20:07 +0300
Message-Id: <20200903082007.18715-1-adrian.hunter@intel.com>
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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>
---
drivers/mmc/core/sdio_ops.c | 39 +++++++++++++++++++++----------------
1 file changed, 22 insertions(+), 17 deletions(-)
diff --git a/drivers/mmc/core/sdio_ops.c b/drivers/mmc/core/sdio_ops.c
index 93d346c01110..4c229dd2b6e5 100644
--- 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 *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)
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