Re: [PATCH] coresight: etm4x: Add support to disable trace unit power up

Good morning Sai,

On Thu, May 14, 2020 at 04:29:15PM +0530, Sai Prakash Ranjan wrote:

From: Tingwei Zhang tingwei@codeaurora.org

On some Qualcomm Technologies Inc. SoCs like SC7180, there exists a hardware errata where the APSS (Application Processor SubSystem)/CPU watchdog counter is stopped when ETM register TRCPDCR.PU=1.

Fun stuff...

Since the ETMs share the same power domain as that of respective CPU cores, they are powered on when the CPU core is powered on. So we can disable powering up of the trace unit after checking for this errata via new property called "qcom,tupwr-disable".

Signed-off-by: Tingwei Zhang tingwei@codeaurora.org Co-developed-by: Sai Prakash Ranjan saiprakash.ranjan@codeaurora.org Signed-off-by: Sai Prakash Ranjan saiprakash.ranjan@codeaurora.org

Co-developed-by: Sai Prakash Ranjan saiprakash.ranjan@codeaurora.org Signed-off-by: Tingwei Zhang tingwei@codeaurora.org

---

.../devicetree/bindings/arm/coresight.txt | 6 ++++ drivers/hwtracing/coresight/coresight-etm4x.c | 29 ++++++++++++-------

Please split in two patches.

2 files changed, 25 insertions(+), 10 deletions(-)

diff --git a/Documentation/devicetree/bindings/arm/coresight.txt b/Documentation/devicetree/bindings/arm/coresight.txt index 846f6daae71b..d2030128fe46 100644 --- a/Documentation/devicetree/bindings/arm/coresight.txt +++ b/Documentation/devicetree/bindings/arm/coresight.txt @@ -108,6 +108,12 @@ its hardware characteristcs.

• arm,cp14: must be present if the system accesses ETM/PTM management registers via co-processor 14.

• • qcom,tupwr-disable: boolean. Indicates that trace unit power up can

•  be disabled on Qualcomm Technologies Inc. systems where ETMs are in
  

•  the same power domain as their CPU cores. This property is required
  

•  to identify such systems with hardware errata where the CPU watchdog
  

•  counter is stopped when TRCPDCR.PU=1.
  

I think something like "qcom,skip-power-up" would be clearer.

Also, a better choice of words is that TRCPDCR.PU does not have to be set on Qualcomm...

• Optional property for TMC:

• arm,buffer-size: size of contiguous buffer space for TMC ETR

diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c index fb0f5f4f3a91..6886b44f6947 100644 --- a/drivers/hwtracing/coresight/coresight-etm4x.c +++ b/drivers/hwtracing/coresight/coresight-etm4x.c @@ -104,6 +104,11 @@ struct etm4_enable_arg { int rc; }; +static inline bool etm4_can_disable_tupwr(struct device *dev) +{

• return fwnode_property_present(dev_fwnode(dev), "qcom,tupwr-disable");

+}

Please call fwnode_property_present() at initialisation time to set a new drvdata::skip_power_up variable. From there just switch on that in etm4_enable/disable_hw().

Thanks, Mathieu

static int etm4_enable_hw(struct etmv4_drvdata *drvdata) { int i, rc; @@ -196,12 +201,14 @@ static int etm4_enable_hw(struct etmv4_drvdata *drvdata) 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);
  

• if (!etm4_can_disable_tupwr(etm_dev)) {

• /*
  

•  * 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); @@ -476,10 +483,12 @@ 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);

• if (!etm4_can_disable_tupwr(etm_dev)) {

• /* 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); -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation