Re: [PATCH V2 3/5] coresight: etm4x: Drop pid argument from etm4_probe()

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On 27/03/2023 06:05, Anshuman Khandual wrote:
Coresight device pid can be retrieved from its iomem base address, which is
stored in 'struct etm4x_drvdata'. This drops pid argument from etm4_probe()
and 'struct etm4_init_arg'. Instead etm4_check_arch_features() derives the
coresight device pid with a new helper coresight_get_pid(), right before it
is consumed in etm4_hisi_match_pid().

Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Cc: Mike Leach <mike.leach@xxxxxxxxxx>
Cc: Leo Yan <leo.yan@xxxxxxxxxx>
Cc: coresight@xxxxxxxxxxxxxxxx
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
---
  .../coresight/coresight-etm4x-core.c          | 21 +++++++------------
  include/linux/coresight.h                     | 12 +++++++++++
  2 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index 5d77571a8df9..3521838ab4fb 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -66,7 +66,6 @@ static u64 etm4_get_access_type(struct etmv4_config *config);
  static enum cpuhp_state hp_online;
struct etm4_init_arg {
-	unsigned int		pid;
  	struct device		*dev;
  	struct csdev_access	*csa;
  };
@@ -370,8 +369,10 @@ static void etm4_disable_arch_specific(struct etmv4_drvdata *drvdata)
  }
static void etm4_check_arch_features(struct etmv4_drvdata *drvdata,
-				      unsigned int id)
+				     struct csdev_access *csa)
  {
+	unsigned int id = coresight_get_pid(csa);
+

This throws up the following error on an ETE.

ete: trying to read unsupported register @fe0

So, I guess this must be performed only for iomem based
devices. System instruction based device must be identified
by MIDR_EL1/REVIDR_EL1 if needed for specific erratum.
This is not required now. So, we could bail out early
if we are system instruction based device.


  	if (etm4_hisi_match_pid(id))
  		set_bit(ETM4_IMPDEF_HISI_CORE_COMMIT, drvdata->arch_features);
  }
@@ -385,7 +386,7 @@ static void etm4_disable_arch_specific(struct etmv4_drvdata *drvdata)
  }
static void etm4_check_arch_features(struct etmv4_drvdata *drvdata,
-				     unsigned int id)
+				     struct csdev_access *csa)
  {
  }
  #endif /* CONFIG_ETM4X_IMPDEF_FEATURE */
@@ -1165,7 +1166,7 @@ static void etm4_init_arch_data(void *info)
  	etm4_os_unlock_csa(drvdata, csa);
  	etm4_cs_unlock(drvdata, csa);
- etm4_check_arch_features(drvdata, init_arg->pid);
+	etm4_check_arch_features(drvdata, csa);
/* find all capabilities of the tracing unit */
  	etmidr0 = etm4x_relaxed_read32(csa, TRCIDR0);
@@ -2048,7 +2049,7 @@ static int etm4_add_coresight_dev(struct etm4_init_arg *init_arg)
  	return 0;
  }
-static int etm4_probe(struct device *dev, u32 etm_pid)
+static int etm4_probe(struct device *dev)
  {
  	struct etmv4_drvdata *drvdata = dev_get_drvdata(dev);
  	struct csdev_access access = { 0 };
@@ -2077,7 +2078,6 @@ static int etm4_probe(struct device *dev, u32 etm_pid)
init_arg.dev = dev;
  	init_arg.csa = &access;
-	init_arg.pid = etm_pid;
/*
  	 * Serialize against CPUHP callbacks to avoid race condition
@@ -2124,7 +2124,7 @@ static int etm4_probe_amba(struct amba_device *adev, const struct amba_id *id)
drvdata->base = base;
  	dev_set_drvdata(dev, drvdata);
-	ret = etm4_probe(dev, id->id);
+	ret = etm4_probe(dev);
  	if (!ret)
  		pm_runtime_put(&adev->dev);
@@ -2146,12 +2146,7 @@ static int etm4_probe_platform_dev(struct platform_device *pdev)
  	pm_runtime_set_active(&pdev->dev);
  	pm_runtime_enable(&pdev->dev);
- /*
-	 * System register based devices could match the
-	 * HW by reading appropriate registers on the HW
-	 * and thus we could skip the PID.
-	 */
-	ret = etm4_probe(&pdev->dev, 0);
+	ret = etm4_probe(&pdev->dev);
pm_runtime_put(&pdev->dev);
  	return ret;
diff --git a/include/linux/coresight.h b/include/linux/coresight.h
index f19a47b9bb5a..f85b041ea475 100644
--- a/include/linux/coresight.h
+++ b/include/linux/coresight.h
@@ -370,6 +370,18 @@ static inline u32 csdev_access_relaxed_read32(struct csdev_access *csa,
  	return csa->read(offset, true, false);
  }
+#define CORESIGHT_PIDRn(i) (0xFE0 + ((i) * 4))
+
+static inline u32 coresight_get_pid(struct csdev_access *csa)
+{
+	u32 i, pid = 0;
+
+	for (i = 0; i < 4; i++)
+		pid |= csdev_access_relaxed_read32(csa, CORESIGHT_PIDRn(i)) << (i * 8);

Given the above, we could make this iomem specific.

Suzuki


+
+	return pid;
+}
+
  static inline u64 csdev_access_relaxed_read_pair(struct csdev_access *csa,
  						 u32 lo_offset, u32 hi_offset)
  {




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