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authorSudeep Holla <sudeep.holla@arm.com>2016-08-25 15:19:08 -0600
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-08-31 13:05:43 +0200
commit46a3d5cdb029471247b7be050332df399eca3ee1 (patch)
tree1d3fca4cdd853df5fb5830c6735a10743f1ba9e9 /drivers/hwtracing
parent1d37ae50671435e842c58b1429dfb0a6d065c42a (diff)
downloadlinux-46a3d5cdb029471247b7be050332df399eca3ee1.tar.bz2
coresight: etm4x: request to retain power to the trace unit when active
The Coresight ETMv4 architecture provides a way to request to keep the power to the trace unit. This might help to collect the traces without the need to disable the CPU power management(entering/exiting deeper idle states). Trace PowerDown Control Register provides powerup request bit which when set requests the system to retain power to the trace unit and emulate the powerdown request. Typically, a trace unit drives a signal to the power controller to request that the trace unit core power domain is powered up. However, if the trace unit and the CPU are in the same power domain then the implementation might combine the trace unit power up status with a signal from the CPU. This patch requests to retain power to the trace unit when active and to remove when inactive. Note this change will only request but the behaviour depends on the implementation. However, it matches the exact behaviour expected when the external debugger is connected with respect to CPU power states. Cc: Mathieu Poirier <mathieu.poirier@linaro.org> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/hwtracing')
-rw-r--r--drivers/hwtracing/coresight/coresight-etm4x.c12
-rw-r--r--drivers/hwtracing/coresight/coresight-etm4x.h3
2 files changed, 15 insertions, 0 deletions
diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
index b3bde2aec2b9..c8c7829f7046 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x.c
@@ -164,6 +164,13 @@ static void etm4_enable_hw(void *info)
writel_relaxed(config->vmid_mask0, drvdata->base + TRCVMIDCCTLR0);
writel_relaxed(config->vmid_mask1, drvdata->base + TRCVMIDCCTLR1);
+ /*
+ * Request to keep the trace unit powered and also
+ * emulation of powerdown
+ */
+ writel_relaxed(readl_relaxed(drvdata->base + TRCPDCR) | TRCPDCR_PU,
+ drvdata->base + TRCPDCR);
+
/* Enable the trace unit */
writel_relaxed(1, drvdata->base + TRCPRGCTLR);
@@ -294,6 +301,11 @@ static void etm4_disable_hw(void *info)
CS_UNLOCK(drvdata->base);
+ /* power can be removed from the trace unit now */
+ control = readl_relaxed(drvdata->base + TRCPDCR);
+ control &= ~TRCPDCR_PU;
+ writel_relaxed(control, drvdata->base + TRCPDCR);
+
control = readl_relaxed(drvdata->base + TRCPRGCTLR);
/* EN, bit[0] Trace unit enable bit */
diff --git a/drivers/hwtracing/coresight/coresight-etm4x.h b/drivers/hwtracing/coresight/coresight-etm4x.h
index 5359c5197c1d..2629954429a1 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x.h
+++ b/drivers/hwtracing/coresight/coresight-etm4x.h
@@ -183,6 +183,9 @@
#define TRCSTATR_IDLE_BIT 0
#define ETM_DEFAULT_ADDR_COMP 0
+/* PowerDown Control Register bits */
+#define TRCPDCR_PU BIT(3)
+
/* secure state access levels */
#define ETM_EXLEVEL_S_APP BIT(8)
#define ETM_EXLEVEL_S_OS BIT(9)