Re: [PATCH V3 3/6] coresight: etm4x: Drop pid argument from etm4_probe()

[Suzuki K Poulose]

On 19/05/2023 06:21, 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          | 29 ++++++++++---------
>   include/linux/coresight.h                     | 12 ++++++++
>   2 files changed, 27 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> index 748d2ef53cb0..914ef6eb85d1 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;
>   };
> @@ -370,9 +369,17 @@ 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)
>   {
> -	if (etm4_hisi_match_pid(id))
> +	/*
> +	 * coresight_get_pid() fetches device PID from the iomem
> +	 * register based accesses, which cannot be performed on
> +	 * system instruction based devices.
> +	 */

Minor nit: Please fix the comment to say something like :

	/*
	 * TRCPIDR* registers are not required for ETMs with system
	 * instructions. They must be identified by the MIDR+REVIDRs.
	 * Skip the TRCPID checks for now.
	 */

Rest looks good to me.

Suzuki