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

On Fri, Sep 03, 2021 at 06:28:54PM -0700, Brian Norris wrote:

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@chromium.org

Thanks for the patch, looks good to me:

Reviewed-by: Leo Yan leo.yan@linaro.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