linux-kernel - [PATCH] coresight: cpu-debug: control default behavior via Kconfig

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Message-Id: <20210903182839.1.I20856983f2841b78936134dcf9cdf6ecafe632b9@changeid>
Date:   Fri,  3 Sep 2021 18:28:54 -0700
From:   Brian Norris <briannorris@...omium.org>
To:     Leo Yan <leo.yan@...aro.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Mike Leach <mike.leach@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>
Cc:     coresight@...ts.linaro.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Brian Norris <briannorris@...omium.org>
Subject: [PATCH] coresight: cpu-debug: control default behavior via Kconfig

Debugfs is nice and so are module parameters, but
 * debugfs doesn't take effect early (e.g., if drivers are locking up
   before user space gets anywhere)
 * module parameters either add a lot to the kernel command line, or
   else take effect late as well (if you build =m and configure in
   /etc/modprobe.d/)

So in the same spirit as these
  CONFIG_PANIC_ON_OOPS (also available via cmdline or modparam)
  CONFIG_INTEL_IOMMU_DEFAULT_ON (also available via cmdline)
add a new Kconfig option.

Module parameters and debugfs can still override.

Signed-off-by: Brian Norris <briannorris@...omium.org>
---

 drivers/hwtracing/coresight/Kconfig               | 13 +++++++++++++
 drivers/hwtracing/coresight/coresight-cpu-debug.c |  2 +-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/hwtracing/coresight/Kconfig b/drivers/hwtracing/coresight/Kconfig
index f026e5c0e777..8b638eb3cb7d 100644
--- a/drivers/hwtracing/coresight/Kconfig
+++ b/drivers/hwtracing/coresight/Kconfig
@@ -150,6 +150,19 @@ config CORESIGHT_CPU_DEBUG
 	  To compile this driver as a module, choose M here: the
 	  module will be called coresight-cpu-debug.
 
+config CORESIGHT_CPU_DEBUG_DEFAULT_ON
+	bool "Enable CoreSight CPU Debug by default
+	depends on CORESIGHT_CPU_DEBUG
+	help
+	  Say Y here to enable the CoreSight Debug panic-debug by default. This
+	  can also be enabled via debugfs, but this ensures the debug feature
+	  is enabled as early as possible.
+
+	  Has the same effect as setting coresight_cpu_debug.enable=1 on the
+	  kernel command line.
+
+	  Say N if unsure.
+
 config CORESIGHT_CTI
 	tristate "CoreSight Cross Trigger Interface (CTI) driver"
 	depends on ARM || ARM64
diff --git a/drivers/hwtracing/coresight/coresight-cpu-debug.c b/drivers/hwtracing/coresight/coresight-cpu-debug.c
index 00de46565bc4..8845ec4b4402 100644
--- a/drivers/hwtracing/coresight/coresight-cpu-debug.c
+++ b/drivers/hwtracing/coresight/coresight-cpu-debug.c
@@ -105,7 +105,7 @@ static DEFINE_PER_CPU(struct debug_drvdata *, debug_drvdata);
 static int debug_count;
 static struct dentry *debug_debugfs_dir;
 
-static bool debug_enable;
+static bool debug_enable = IS_ENABLED(CONFIG_CORESIGHT_CPU_DEBUG_DEFAULT_ON);
 module_param_named(enable, debug_enable, bool, 0600);
 MODULE_PARM_DESC(enable, "Control to enable coresight CPU debug functionality");
 
-- 
2.33.0.153.gba50c8fa24-goog