Re: [PATCH V3 3/4] coresight: trbe: Add a representative coresight_platform_data for TRBE

From: Suzuki K Poulose
Date: Fri Aug 04 2023 - 06:04:37 EST


On 04/08/2023 10:18, Anshuman Khandual wrote:


On 8/3/23 19:25, Suzuki K Poulose wrote:
On 03/08/2023 06:56, Anshuman Khandual wrote:
TRBE coresight devices do not need regular connections information, as the
paths get built between all percpu source and their respective percpu sink
devices. Please refer 'commit 2cd87a7b293d ("coresight: core: Add support
for dedicated percpu sinks")' which added support for percpu sink devices.

coresight_register() expect device connections via the platform_data. TRBE
devices do not have any graph connections and thus is empty. With upcoming
ACPI support for TRBE, we do not get a real acpi_device and thus
coresight_get_platform_dat() will end up in failures. Hence this allocates
a zeroed coresight_platform_data structure and assigns that back into the
device.

Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Cc: Mike Leach <mike.leach@xxxxxxxxxx>
Cc: Leo Yan <leo.yan@xxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: coresight@xxxxxxxxxxxxxxxx
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
---
  drivers/hwtracing/coresight/coresight-trbe.c | 6 +++---
  1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c
index 7720619909d6..e1d9d06e7725 100644
--- a/drivers/hwtracing/coresight/coresight-trbe.c
+++ b/drivers/hwtracing/coresight/coresight-trbe.c
@@ -1494,9 +1494,9 @@ static int arm_trbe_device_probe(struct platform_device *pdev)
      if (!drvdata)
          return -ENOMEM;
  -    pdata = coresight_get_platform_data(dev);
-    if (IS_ERR(pdata))
-        return PTR_ERR(pdata);
+    pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
+    if (!pdata)
+        return -ENOMEM;

Please could you add a comment in here, on why we use a dummy platform
data ? It is good to have documented it in the code too.

Sure, will add the following in-code documentation.

+ /*
+ * TRBE coresight devices do not need regular connections
+ * information, as the paths get built between all percpu
+ * source and their respective percpu sink devices. Though
+ * coresight_register() expect device connections via the
+ * platform_data, which TRBE devices do not have. As they
+ * are not real ACPI devices, coresight_get_platform_dat()

minor nit: s/coresight_get_platform_dat/coresight_get_platform_data/
here and above in the description.

Otherwise, looks good.

Suzuki