Re: [PATCH v8 3/7] coresight: core: Add provision for panic callbacks

[James Clark]

On 31/05/2024 05:27, Linu Cherian wrote:
> Panic callback handlers allows coresight device drivers to sync
> relevant trace data and trace metadata to reserved memory
> regions so that they can be retrieved later in the subsequent
> boot or in the crashdump kernel.
> 
> Signed-off-by: Linu Cherian <lcherian@xxxxxxxxxxx>
> ---

Reviewed-by: James Clark <james.clark@xxxxxxx>

>  drivers/hwtracing/coresight/coresight-core.c | 37 ++++++++++++++++++++
>  include/linux/coresight.h                    | 12 +++++++
>  2 files changed, 49 insertions(+)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
> index b83613e34289..61d75aad476b 100644
> --- a/drivers/hwtracing/coresight/coresight-core.c
> +++ b/drivers/hwtracing/coresight/coresight-core.c
> @@ -19,6 +19,7 @@
>  #include <linux/property.h>
>  #include <linux/delay.h>
>  #include <linux/pm_runtime.h>
> +#include <linux/panic_notifier.h>
>  
>  #include "coresight-etm-perf.h"
>  #include "coresight-priv.h"
> @@ -1365,6 +1366,36 @@ const struct bus_type coresight_bustype = {
>  	.name	= "coresight",
>  };
>  
> +static int coresight_panic_sync(struct device *dev, void *data)
> +{
> +	int mode;
> +	struct coresight_device *csdev;
> +
> +	/* Run through panic sync handlers for all enabled devices */
> +	csdev = container_of(dev, struct coresight_device, dev);
> +	mode = coresight_get_mode(csdev);
> +
> +	if ((mode == CS_MODE_SYSFS) || (mode == CS_MODE_PERF)) {
> +		if (panic_ops(csdev))
> +			panic_ops(csdev)->sync(csdev);
> +	}
> +
> +	return 0;
> +}
> +
> +static int coresight_panic_cb(struct notifier_block *self,
> +			       unsigned long v, void *p)
> +{
> +	bus_for_each_dev(&coresight_bustype, NULL, NULL,
> +				 coresight_panic_sync);
> +
> +	return 0;
> +}
> +
> +static struct notifier_block coresight_notifier = {
> +	.notifier_call = coresight_panic_cb,
> +};
> +
>  static int __init coresight_init(void)
>  {
>  	int ret;
> @@ -1377,6 +1408,10 @@ static int __init coresight_init(void)
>  	if (ret)
>  		goto exit_bus_unregister;
>  
> +	/* Register function to be called for panic */
> +	ret = atomic_notifier_chain_register(&panic_notifier_list,
> +					     &coresight_notifier);
> +
>  	/* initialise the coresight syscfg API */
>  	ret = cscfg_init();
>  	if (!ret)
> @@ -1391,6 +1426,8 @@ static int __init coresight_init(void)
>  static void __exit coresight_exit(void)
>  {
>  	cscfg_exit();
> +	atomic_notifier_chain_unregister(&panic_notifier_list,
> +					     &coresight_notifier);
>  	etm_perf_exit();
>  	bus_unregister(&coresight_bustype);
>  }
> diff --git a/include/linux/coresight.h b/include/linux/coresight.h
> index 5f288d475490..b156467c9baa 100644
> --- a/include/linux/coresight.h
> +++ b/include/linux/coresight.h
> @@ -315,6 +315,7 @@ enum cs_mode {
>  #define link_ops(csdev)		csdev->ops->link_ops
>  #define helper_ops(csdev)	csdev->ops->helper_ops
>  #define ect_ops(csdev)		csdev->ops->ect_ops
> +#define panic_ops(csdev)	csdev->ops->panic_ops
>  
>  /**
>   * struct coresight_ops_sink - basic operations for a sink
> @@ -384,11 +385,22 @@ struct coresight_ops_helper {
>  	int (*disable)(struct coresight_device *csdev, void *data);
>  };
>  
> +
> +/**
> + * struct coresight_ops_panic - Generic device ops for panic handing
> + *
> + * @sync	: Sync the device register state/trace data
> + */
> +struct coresight_ops_panic {
> +	int (*sync)(struct coresight_device *csdev);
> +};
> +
>  struct coresight_ops {
>  	const struct coresight_ops_sink *sink_ops;
>  	const struct coresight_ops_link *link_ops;
>  	const struct coresight_ops_source *source_ops;
>  	const struct coresight_ops_helper *helper_ops;
> +	const struct coresight_ops_panic *panic_ops;
>  };
>  
>  static inline u32 csdev_access_relaxed_read32(struct csdev_access *csa,