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From:   Bhupesh Sharma <bhupesh.sharma@linaro.org>
To:     coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org
Cc:     mathieu.poirier@linaro.org, suzuki.poulose@arm.com,
        mike.leach@linaro.org, leo.yan@linaro.org,
        alexander.shishkin@linux.intel.com, linux-kernel@vger.kernel.org,
        bhupesh.linux@gmail.com,
        Bhupesh Sharma <bhupesh.sharma@linaro.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: [PATCH] coresight: etm4x: Fix crash observed on Qcom ETM parts with 'Low power override'
Date:   Thu,  4 Aug 2022 00:42:36 +0530
Message-Id: <20220803191236.3037591-1-bhupesh.sharma@linaro.org>
MIME-Version: 1.0
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Some Qualcomm ETM implementations require skipping powering up
the trace unit, as the ETMs are in the same power domain as
their CPU cores.

Via commit 5214b563588e ("coresight: etm4x: Add support for
sysreg only devices"), the setting of 'skip_power_up' flag was
moved after the 'etm4_init_arch_data' function is called, whereas
the flag value is itself used inside the function. This causes
a crash when ETM mode 'Low-power state behavior override' is set
on some Qualcomm parts.

Fix the same.

Fixes: 5214b563588e ("coresight: etm4x: Add support for sysreg only devices")
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Bhupesh Sharma <bhupesh.sharma@linaro.org>
---
 drivers/hwtracing/coresight/coresight-etm4x-core.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index d39660a3e50c..cf6254b87fd5 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -1943,6 +1943,16 @@ static int etm4_probe(struct device *dev, void __iomem *base, u32 etm_pid)
 	init_arg.csa = &desc.access;
 	init_arg.pid = etm_pid;
 
+	/*
+	 * Some Qualcomm implementations require skipping powering up the trace unit,
+	 * as the ETMs are in the same power domain as their CPU cores.
+	 *
+	 * Since the 'skip_power_up' flag is used inside 'etm4_init_arch_data' function,
+	 * initialize it before the function is called.
+	 */
+	if (fwnode_property_present(dev_fwnode(dev), "qcom,skip-power-up"))
+		drvdata->skip_power_up = true;
+
 	if (smp_call_function_single(drvdata->cpu,
 				etm4_init_arch_data,  &init_arg, 1))
 		dev_err(dev, "ETM arch init failed\n");
@@ -1951,8 +1961,7 @@ static int etm4_probe(struct device *dev, void __iomem *base, u32 etm_pid)
 		return -EINVAL;
 
 	/* TRCPDCR is not accessible with system instructions. */
-	if (!desc.access.io_mem ||
-	    fwnode_property_present(dev_fwnode(dev), "qcom,skip-power-up"))
+	if (!desc.access.io_mem)
 		drvdata->skip_power_up = true;
 
 	major = ETM_ARCH_MAJOR_VERSION(drvdata->arch);
-- 
2.35.3