linux-kernel - [PATCH 1/3] mmc: core: Avoid hogging the CPU while polling for busy in the I/O err path

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Date:   Fri,  2 Jul 2021 15:42:27 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     linux-mmc@...r.kernel.org, Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Adrian Hunter <adrian.hunter@...el.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Christian Lohle <CLoehle@...erstone.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] mmc: core: Avoid hogging the CPU while polling for busy in the I/O err path

When mmc_blk_fix_state() sends a CMD12 to try to move the card into the
transfer state, it calls card_busy_detect() to poll for the card's state
with CMD13. This is done without any delays in between the commands being
sent.

Rather than fixing card_busy_detect() in this regards, let's instead
convert into using the common mmc_poll_for_busy(), which also helps us to
avoid open-coding.

Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
---
 drivers/mmc/core/block.c   | 2 +-
 drivers/mmc/core/mmc_ops.c | 4 +++-
 drivers/mmc/core/mmc_ops.h | 1 +
 3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
index 88f4c215caa6..1b5576048cdb 100644
--- a/drivers/mmc/core/block.c
+++ b/drivers/mmc/core/block.c
@@ -1630,7 +1630,7 @@ static int mmc_blk_fix_state(struct mmc_card *card, struct request *req)
 
 	mmc_blk_send_stop(card, timeout);
 
-	err = card_busy_detect(card, timeout, NULL);
+	err = mmc_poll_for_busy(card, timeout, false, MMC_BUSY_IO);
 
 	mmc_retune_release(card->host);
 
diff --git a/drivers/mmc/core/mmc_ops.c b/drivers/mmc/core/mmc_ops.c
index 973756ed4016..e2c431c0ce5d 100644
--- a/drivers/mmc/core/mmc_ops.c
+++ b/drivers/mmc/core/mmc_ops.c
@@ -435,7 +435,7 @@ static int mmc_busy_cb(void *cb_data, bool *busy)
 	u32 status = 0;
 	int err;
 
-	if (host->ops->card_busy) {
+	if (data->busy_cmd != MMC_BUSY_IO && host->ops->card_busy) {
 		*busy = host->ops->card_busy(host);
 		return 0;
 	}
@@ -457,6 +457,7 @@ static int mmc_busy_cb(void *cb_data, bool *busy)
 		break;
 	case MMC_BUSY_HPI:
 	case MMC_BUSY_EXTR_SINGLE:
+	case MMC_BUSY_IO:
 		break;
 	default:
 		err = -EINVAL;
@@ -521,6 +522,7 @@ int mmc_poll_for_busy(struct mmc_card *card, unsigned int timeout_ms,
 
 	return __mmc_poll_for_busy(card, timeout_ms, &mmc_busy_cb, &cb_data);
 }
+EXPORT_SYMBOL_GPL(mmc_poll_for_busy);
 
 bool mmc_prepare_busy_cmd(struct mmc_host *host, struct mmc_command *cmd,
 			  unsigned int timeout_ms)
diff --git a/drivers/mmc/core/mmc_ops.h b/drivers/mmc/core/mmc_ops.h
index 41ab4f573a31..ae25ffc2e870 100644
--- a/drivers/mmc/core/mmc_ops.h
+++ b/drivers/mmc/core/mmc_ops.h
@@ -15,6 +15,7 @@ enum mmc_busy_cmd {
 	MMC_BUSY_ERASE,
 	MMC_BUSY_HPI,
 	MMC_BUSY_EXTR_SINGLE,
+	MMC_BUSY_IO,
 };
 
 struct mmc_host;
-- 
2.25.1