linux-kernel - [PATCH v4 02/25] coresight: etm4x: Skip accessing TRCPDCR in save/restore

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Message-Id: <20201119164547.2982871-3-suzuki.poulose@arm.com>
Date:   Thu, 19 Nov 2020 16:45:24 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     mathieu.poirier@...aro.org, mike.leach@...aro.org,
        linux-kernel@...r.kernel.org, anshuman.khandual@....com,
        jonathan.zhouwen@...wei.com, coresight@...ts.linaro.org,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        Tingwei Zhang <tingwei@...eaurora.org>
Subject: [PATCH v4 02/25] coresight: etm4x: Skip accessing TRCPDCR in save/restore

When the ETM is affected by Qualcomm errata, modifying the
TRCPDCR could cause the system hang. Even though this is
taken care of during enable/disable ETM, the ETM state
save/restore could still access the TRCPDCR. Make sure
we skip the access during the save/restore.

Found by code inspection.

Fixes: commit 02510a5aa78df45 ("coresight: etm4x: Add support to skip trace unit power up")
Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
Cc: Mike Leach <mike.leach@...aro.org>
Cc: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
Cc: Tingwei Zhang <tingwei@...eaurora.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
---
 drivers/hwtracing/coresight/coresight-etm4x-core.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index 59a4a166adf4..ea2e317ddb7d 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -1277,7 +1277,8 @@ static int etm4_cpu_save(struct etmv4_drvdata *drvdata)
 
 	state->trcclaimset = readl(drvdata->base + TRCCLAIMCLR);
 
-	state->trcpdcr = readl(drvdata->base + TRCPDCR);
+	if (!drvdata->skip_power_up)
+		state->trcpdcr = readl(drvdata->base + TRCPDCR);
 
 	/* wait for TRCSTATR.IDLE to go up */
 	if (coresight_timeout(drvdata->base, TRCSTATR, TRCSTATR_IDLE_BIT, 1)) {
@@ -1295,9 +1296,9 @@ static int etm4_cpu_save(struct etmv4_drvdata *drvdata)
 	 * potentially save power on systems that respect the TRCPDCR_PU
 	 * despite requesting software to save/restore state.
 	 */
-	writel_relaxed((state->trcpdcr & ~TRCPDCR_PU),
-			drvdata->base + TRCPDCR);
-
+	if (!drvdata->skip_power_up)
+		writel_relaxed((state->trcpdcr & ~TRCPDCR_PU),
+				drvdata->base + TRCPDCR);
 out:
 	CS_LOCK(drvdata->base);
 	return ret;
@@ -1392,7 +1393,8 @@ static void etm4_cpu_restore(struct etmv4_drvdata *drvdata)
 
 	writel_relaxed(state->trcclaimset, drvdata->base + TRCCLAIMSET);
 
-	writel_relaxed(state->trcpdcr, drvdata->base + TRCPDCR);
+	if (!drvdata->skip_power_up)
+		writel_relaxed(state->trcpdcr, drvdata->base + TRCPDCR);
 
 	drvdata->state_needs_restore = false;
 
-- 
2.24.1