linux-kernel - [PATCH v3] mmc: Change the max discard sectors and erase response if mmc host supports busy signalling

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Date:	Mon, 25 Jul 2016 16:48:39 +0800
From:	Baolin Wang <baolin.wang@...aro.org>
To:	ulf.hansson@...aro.org
Cc:	adrian.hunter@...el.com, rmk+kernel@....linux.org.uk,
	shawn.lin@...k-chips.com, dianders@...omium.org, heiko@...ech.de,
	david@...tonic.nl, hdegoede@...hat.com, linux-mmc@...r.kernel.org,
	linux-kernel@...r.kernel.org, broonie@...nel.org,
	linus.walleij@...aro.org, baolin.wang@...aro.org
Subject: [PATCH v3] mmc: Change the max discard sectors and erase response if mmc host supports busy signalling

When mmc host HW supports busy signalling (using R1B as response), We
shouldn't use 'host->max_busy_timeout' as the limitation when deciding
the max discard sectors that we tell the generic BLOCK layer about.
Instead, we should pick one preferred erase size as the max discard
sectors.

If the host controller supports busy signalling and the timeout for
the erase operation does not exceed the max_busy_timeout, we should
use R1B response. Or we need to prevent the host from doing hw busy
detection, which is done by converting to a R1 response instead.

Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
---
Changes since v2:
  - Remove the 'MMC_CAP_WAIT_WHILE_BUSY' flag checking when deciding
  if we can use R1B response.
  - Avoid polling CMD13 when using R1B response.
  - Use earlier calculated erase timeout as the polling time.

Changes since v1:
  - Remove the 'MMC_CAP_WAIT_WHILE_BUSY' flag checking when deciding
    the max discard sectors.
---
 drivers/mmc/core/core.c |   60 +++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 50 insertions(+), 10 deletions(-)

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 8b4dfd4..b4c08d1a 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -2060,7 +2060,8 @@ static int mmc_do_erase(struct mmc_card *card, unsigned int from,
 			unsigned int to, unsigned int arg)
 {
 	struct mmc_command cmd = {0};
-	unsigned int qty = 0;
+	unsigned int qty = 0, busy_timeout = 0;
+	bool use_r1b_resp = false;
 	unsigned long timeout;
 	int err;
 
@@ -2128,8 +2129,22 @@ static int mmc_do_erase(struct mmc_card *card, unsigned int from,
 	memset(&cmd, 0, sizeof(struct mmc_command));
 	cmd.opcode = MMC_ERASE;
 	cmd.arg = arg;
-	cmd.flags = MMC_RSP_SPI_R1B | MMC_RSP_R1B | MMC_CMD_AC;
-	cmd.busy_timeout = mmc_erase_timeout(card, arg, qty);
+	busy_timeout = mmc_erase_timeout(card, arg, qty);
+	/*
+	 * If the host controller supports busy signalling and the timeout for
+	 * the erase operation does not exceed the max_busy_timeout, we should
+	 * use R1B response. Or we need to prevent the host from doing hw busy
+	 * detection, which is done by converting to a R1 response instead.
+	 */
+	if (card->host->max_busy_timeout &&
+	    busy_timeout > card->host->max_busy_timeout) {
+		cmd.flags = MMC_RSP_SPI_R1 | MMC_RSP_R1 | MMC_CMD_AC;
+	} else {
+		cmd.flags = MMC_RSP_SPI_R1B | MMC_RSP_R1B | MMC_CMD_AC;
+		cmd.busy_timeout = busy_timeout;
+		use_r1b_resp = true;
+	}
+
 	err = mmc_wait_for_cmd(card->host, &cmd, 0);
 	if (err) {
 		pr_err("mmc_erase: erase error %d, status %#x\n",
@@ -2141,7 +2156,14 @@ static int mmc_do_erase(struct mmc_card *card, unsigned int from,
 	if (mmc_host_is_spi(card->host))
 		goto out;
 
-	timeout = jiffies + msecs_to_jiffies(MMC_CORE_TIMEOUT_MS);
+	/*
+	 * In case of when R1B + MMC_CAP_WAIT_WHILE_BUSY is used, the polling
+	 * shall be avoided.
+	 */
+	if ((card->host->caps & MMC_CAP_WAIT_WHILE_BUSY) && use_r1b_resp)
+		goto out;
+
+	timeout = jiffies + msecs_to_jiffies(busy_timeout);
 	do {
 		memset(&cmd, 0, sizeof(struct mmc_command));
 		cmd.opcode = MMC_SEND_STATUS;
@@ -2321,23 +2343,41 @@ static unsigned int mmc_do_calc_max_discard(struct mmc_card *card,
 					    unsigned int arg)
 {
 	struct mmc_host *host = card->host;
-	unsigned int max_discard, x, y, qty = 0, max_qty, timeout;
+	unsigned int max_discard, x, y, qty = 0, max_qty, min_qty, timeout;
 	unsigned int last_timeout = 0;
 
-	if (card->erase_shift)
+	if (card->erase_shift) {
 		max_qty = UINT_MAX >> card->erase_shift;
-	else if (mmc_card_sd(card))
+		min_qty = card->pref_erase >> card->erase_shift;
+	} else if (mmc_card_sd(card)) {
 		max_qty = UINT_MAX;
-	else
+		min_qty = card->pref_erase;
+	} else {
 		max_qty = UINT_MAX / card->erase_size;
+		min_qty = card->pref_erase / card->erase_size;
+	}
 
-	/* Find the largest qty with an OK timeout */
+	/*
+	 * We should not only use 'host->max_busy_timeout' as the limitation
+	 * when deciding the max discard sectors. We should set a balance value
+	 * to improve the erase speed, and it can not get too long timeout at
+	 * the same time.
+	 *
+	 * Here we set 'card->pref_erase' as the minimal discard sectors no
+	 * matter what size of 'host->max_busy_timeout', but if the
+	 * 'host->max_busy_timeout' is large enough for more discard sectors,
+	 * then we can continue to increase the max discard sectors until we
+	 * get a balance value.
+	 */
 	do {
 		y = 0;
 		for (x = 1; x && x <= max_qty && max_qty - x >= qty; x <<= 1) {
 			timeout = mmc_erase_timeout(card, arg, qty + x);
-			if (timeout > host->max_busy_timeout)
+
+			if (qty + x > min_qty &&
+			    timeout > host->max_busy_timeout)
 				break;
+
 			if (timeout < last_timeout)
 				break;
 			last_timeout = timeout;
-- 
1.7.9.5