linux-kernel - [PATCH V1] mmc: sdhci: Check for reset prior to DMA address unmap

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Date:   Wed, 24 Feb 2021 16:23:05 +0530
From:   Pradeep P V K <pragalla@...eaurora.org>
To:     adrian.hunter@...el.com, ulf.hansson@...aro.org
Cc:     asutoshd@...eaurora.org, stummala@...eaurora.org,
        rampraka@...eaurora.org, vbadigan@...eaurora.org,
        linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Pradeep P V K <pragalla@...eaurora.org>
Subject: [PATCH V1] mmc: sdhci: Check for reset prior to DMA address unmap

For data read commands, SDHC may initiate data transfers even before it
completely process the command response. In case command itself fails,
driver un-maps the memory associated with data transfer but this memory
can still be accessed by SDHC for the already initiated data transfer.
This scenario can lead to un-mapped memory access error.

To avoid this scenario, reset SDHC (when command fails) prior to
un-mapping memory. Resetting SDHC ensures that all in-flight data
transfers are either aborted or completed. So we don't run into this
scenario.

Swap the reset, un-map steps sequence in sdhci_request_done().

Suggested-by: Veerabhadrarao Badiganti <vbadigan@...eaurora.org>
Signed-off-by: Pradeep P V K <pragalla@...eaurora.org>
---
 drivers/mmc/host/sdhci.c | 58 ++++++++++++++++++++++++------------------------
 1 file changed, 29 insertions(+), 29 deletions(-)

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 646823d..e78d84c 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -2996,6 +2996,35 @@ static bool sdhci_request_done(struct sdhci_host *host)
 		spin_unlock_irqrestore(&host->lock, flags);
 		return true;
 	}
+	/*
+	 * The controller needs a reset of internal state machines
+	 * upon error conditions.
+	 */
+	if (sdhci_needs_reset(host, mrq)) {
+		/*
+		 * Do not finish until command and data lines are available for
+		 * reset. Note there can only be one other mrq, so it cannot
+		 * also be in mrqs_done, otherwise host->cmd and host->data_cmd
+		 * would both be null.
+		 */
+		if (host->cmd || host->data_cmd) {
+			spin_unlock_irqrestore(&host->lock, flags);
+			return true;
+		}
+
+		/* Some controllers need this kick or reset won't work here */
+		if (host->quirks & SDHCI_QUIRK_CLOCK_BEFORE_RESET)
+			/* This is to force an update */
+			host->ops->set_clock(host, host->clock);
+
+		/* Spec says we should do both at the same time, but Ricoh
+		 * controllers do not like that.
+		 */
+		sdhci_do_reset(host, SDHCI_RESET_CMD);
+		sdhci_do_reset(host, SDHCI_RESET_DATA);
+
+		host->pending_reset = false;
+	}
 
 	/*
 	 * Always unmap the data buffers if they were mapped by
@@ -3060,35 +3089,6 @@ static bool sdhci_request_done(struct sdhci_host *host)
 		}
 	}
 
-	/*
-	 * The controller needs a reset of internal state machines
-	 * upon error conditions.
-	 */
-	if (sdhci_needs_reset(host, mrq)) {
-		/*
-		 * Do not finish until command and data lines are available for
-		 * reset. Note there can only be one other mrq, so it cannot
-		 * also be in mrqs_done, otherwise host->cmd and host->data_cmd
-		 * would both be null.
-		 */
-		if (host->cmd || host->data_cmd) {
-			spin_unlock_irqrestore(&host->lock, flags);
-			return true;
-		}
-
-		/* Some controllers need this kick or reset won't work here */
-		if (host->quirks & SDHCI_QUIRK_CLOCK_BEFORE_RESET)
-			/* This is to force an update */
-			host->ops->set_clock(host, host->clock);
-
-		/* Spec says we should do both at the same time, but Ricoh
-		   controllers do not like that. */
-		sdhci_do_reset(host, SDHCI_RESET_CMD);
-		sdhci_do_reset(host, SDHCI_RESET_DATA);
-
-		host->pending_reset = false;
-	}
-
 	host->mrqs_done[i] = NULL;
 
 	spin_unlock_irqrestore(&host->lock, flags);
-- 
2.7.4