coresight: etm4x: Handle accesses to TRCSTALLCTLR

TRCSTALLCTLR register is only implemented if

   TRCIDR3.STALLCTL == 0b1

Make sure the driver touches the register only it is implemented.

Link: https://lore.kernel.org/r/20210127184617.3684379-1-suzuki.poulose@arm.com
Cc: stable@vger.kernel.org
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Leo Yan <leo.yan@linaro.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/20210201181351.1475223-32-mathieu.poirier@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hwtracing/coresight/coresight-etm4x-core.c

@@ -306,7 +306,8 @@ static int etm4_enable_hw(struct etmv4_drvdata *drvdata)
 	etm4x_relaxed_write32(csa, 0x0, TRCAUXCTLR);
 	etm4x_relaxed_write32(csa, config->eventctrl0, TRCEVENTCTL0R);
 	etm4x_relaxed_write32(csa, config->eventctrl1, TRCEVENTCTL1R);
-	etm4x_relaxed_write32(csa, config->stall_ctrl, TRCSTALLCTLR);
+	if (drvdata->stallctl)
+		etm4x_relaxed_write32(csa, config->stall_ctrl, TRCSTALLCTLR);
 	etm4x_relaxed_write32(csa, config->ts_ctrl, TRCTSCTLR);
 	etm4x_relaxed_write32(csa, config->syncfreq, TRCSYNCPR);
 	etm4x_relaxed_write32(csa, config->ccctlr, TRCCCCTLR);
@@ -1463,7 +1464,8 @@ static int etm4_cpu_save(struct etmv4_drvdata *drvdata)
 	state->trcauxctlr = etm4x_read32(csa, TRCAUXCTLR);
 	state->trceventctl0r = etm4x_read32(csa, TRCEVENTCTL0R);
 	state->trceventctl1r = etm4x_read32(csa, TRCEVENTCTL1R);
-	state->trcstallctlr = etm4x_read32(csa, TRCSTALLCTLR);
+	if (drvdata->stallctl)
+		state->trcstallctlr = etm4x_read32(csa, TRCSTALLCTLR);
 	state->trctsctlr = etm4x_read32(csa, TRCTSCTLR);
 	state->trcsyncpr = etm4x_read32(csa, TRCSYNCPR);
 	state->trcccctlr = etm4x_read32(csa, TRCCCCTLR);
@@ -1575,7 +1577,8 @@ static void etm4_cpu_restore(struct etmv4_drvdata *drvdata)
 	etm4x_relaxed_write32(csa, state->trcauxctlr, TRCAUXCTLR);
 	etm4x_relaxed_write32(csa, state->trceventctl0r, TRCEVENTCTL0R);
 	etm4x_relaxed_write32(csa, state->trceventctl1r, TRCEVENTCTL1R);
-	etm4x_relaxed_write32(csa, state->trcstallctlr, TRCSTALLCTLR);
+	if (drvdata->stallctl)
+		etm4x_relaxed_write32(csa, state->trcstallctlr, TRCSTALLCTLR);
 	etm4x_relaxed_write32(csa, state->trctsctlr, TRCTSCTLR);
 	etm4x_relaxed_write32(csa, state->trcsyncpr, TRCSYNCPR);
 	etm4x_relaxed_write32(csa, state->trcccctlr, TRCCCCTLR);

drivers/hwtracing/coresight/coresight-etm4x-sysfs.c

@@ -389,7 +389,7 @@ static ssize_t mode_store(struct device *dev,
 		config->eventctrl1 &= ~BIT(12);
 
 	/* bit[8], Instruction stall bit */
-	if (config->mode & ETM_MODE_ISTALL_EN)
+	if ((config->mode & ETM_MODE_ISTALL_EN) && (drvdata->stallctl == true))
 		config->stall_ctrl |= BIT(8);
 	else
 		config->stall_ctrl &= ~BIT(8);