linux-kernel - [PATCH 1/4] mmc: mmci: avoid fake busy polling

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Date:   Tue, 5 Mar 2019 17:10:02 +0100
From:   Ludovic Barre <ludovic.Barre@...com>
To:     Ulf Hansson <ulf.hansson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>
CC:     <srinivas.kandagatla@...aro.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-mmc@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        Ludovic Barre <ludovic.barre@...com>
Subject: [PATCH  1/4] mmc: mmci: avoid fake busy polling

From: Ludovic Barre <ludovic.barre@...com>

The busy status bit could occurred even if no busy response is
expected (example cmd11). On sdmmc variant, the busy_detect_flag
reflects inverted value of d0 state, it's sampled at the end of a
CMD response and a second time 2 clk cycles after the CMD response.
To avoid a fake busy, the busy status could be checked and polled
only if the command has RSP_BUSY flag.

Signed-off-by: Ludovic Barre <ludovic.barre@...com>
---
 drivers/mmc/host/mmci.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
index 387ff14..4901b73 100644
--- a/drivers/mmc/host/mmci.c
+++ b/drivers/mmc/host/mmci.c
@@ -1220,12 +1220,13 @@ mmci_cmd_irq(struct mmci_host *host, struct mmc_command *cmd,
 	     unsigned int status)
 {
 	void __iomem *base = host->base;
-	bool sbc;
+	bool sbc, busy_resp;
 
 	if (!cmd)
 		return;
 
 	sbc = (cmd == host->mrq->sbc);
+	busy_resp = !!(cmd->flags & MMC_RSP_BUSY);
 
 	/*
 	 * We need to be one of these interrupts to be considered worth
@@ -1239,8 +1240,7 @@ mmci_cmd_irq(struct mmci_host *host, struct mmc_command *cmd,
 	/*
 	 * ST Micro variant: handle busy detection.
 	 */
-	if (host->variant->busy_detect) {
-		bool busy_resp = !!(cmd->flags & MMC_RSP_BUSY);
+	if (busy_resp && host->variant->busy_detect) {
 
 		/* We are busy with a command, return */
 		if (host->busy_status &&
@@ -1253,7 +1253,7 @@ mmci_cmd_irq(struct mmci_host *host, struct mmc_command *cmd,
 		 * that the special busy status bit is still set before
 		 * proceeding.
 		 */
-		if (!host->busy_status && busy_resp &&
+		if (!host->busy_status &&
 		    !(status & (MCI_CMDCRCFAIL|MCI_CMDTIMEOUT)) &&
 		    (readl(base + MMCISTATUS) & host->variant->busy_detect_flag)) {
 
@@ -1508,6 +1508,7 @@ static irqreturn_t mmci_irq(int irq, void *dev_id)
 {
 	struct mmci_host *host = dev_id;
 	u32 status;
+	bool busy_resp;
 	int ret = 0;
 
 	spin_lock(&host->lock);
@@ -1550,9 +1551,15 @@ static irqreturn_t mmci_irq(int irq, void *dev_id)
 		}
 
 		/*
-		 * Don't poll for busy completion in irq context.
+		 * Don't poll for:
+		 * -busy completion in irq context.
+		 * -no busy response expected.
 		 */
-		if (host->variant->busy_detect && host->busy_status)
+		busy_resp = host->cmd ?
+			!!(host->cmd->flags & MMC_RSP_BUSY) : false;
+
+		if (host->variant->busy_detect &&
+		    (!busy_resp || host->busy_status))
 			status &= ~host->variant->busy_detect_flag;
 
 		ret = 1;
-- 
2.7.4