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.

Link: https://lore.kernel.org/r/20210110224850.1880240-3-suzuki.poulose@arm.com
Fixes: 02510a5aa78d ("coresight: etm4x: Add support to skip trace unit power up")
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Cc: Tingwei Zhang <tingwei@codeaurora.org>
Tested-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Reviewed-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20210201181351.1475223-5-mathieu.poirier@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index 4b615e9..0924c37 100644 (file)
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -1373,7 +1373,8 @@ 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)) {
@@ -1391,9 +1392,9 @@ 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;
@@ -1488,7 +1489,8 @@ 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;