linux-kernel - Re: [PATCH v2 2/8] coresight: Convert tag clear function to take a struct cs

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Message-ID: <cc68d43f-4719-4f57-a38c-fb5afe8d29cc@arm.com>
Date: Wed, 19 Mar 2025 12:00:05 +0000
From: Suzuki K Poulose <suzuki.poulose@....com>
To: James Clark <james.clark@...aro.org>, Mike Leach <mike.leach@...aro.org>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Maxime Coquelin <mcoquelin.stm32@...il.com>,
 Alexandre Torgue <alexandre.torgue@...s.st.com>, leo.yan@....com
Cc: coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH v2 2/8] coresight: Convert tag clear function to take a
 struct cs_access

On 18/03/2025 16:21, James Clark wrote:
> The self hosted claim tag will be reset on device probe in a later
> commit. We'll want to do this before coresight_register() is called so
> won't have a coresight_device and have to use cs_access instead.
> 
> Also make them public and create locked and unlocked versions for
> later use.
> 
> Signed-off-by: James Clark <james.clark@...aro.org>

minor nit:

The restructuring looks a bit confusing. Could we start with :

coresight_{set,clear}_self_claim_tag_unlocked in Patch 1. Rather
than rename what we renamed in patch 1 again here.


> ---
>   drivers/hwtracing/coresight/coresight-core.c | 17 +++++++++++++----
>   include/linux/coresight.h                    |  3 ++-
>   2 files changed, 15 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
> index 3f1c996d668a..9ff601e2415a 100644
> --- a/drivers/hwtracing/coresight/coresight-core.c
> +++ b/drivers/hwtracing/coresight/coresight-core.c
> @@ -151,12 +151,21 @@ static inline void coresight_set_self_claim_tag(struct coresight_device *csdev)
>   	isb();
>   }
>   
> -static inline void coresight_clear_self_claim_tag(struct coresight_device *csdev)
> +void coresight_clear_self_claim_tag(struct csdev_access *csa)
>   {
> -	csdev_access_relaxed_write32(&csdev->access, CORESIGHT_CLAIM_SELF_HOSTED,
> +	CS_UNLOCK(csa->base);

This looks to be hard coding MMIO based access ? Should we abstract it 
based on the csdev_access_** ?


Suzuki


> +	coresight_clear_self_claim_tag_unlocked(csa);
> +	CS_LOCK(csa->base);
> +}
> +EXPORT_SYMBOL_GPL(coresight_clear_self_claim_tag);
> +
> +void coresight_clear_self_claim_tag_unlocked(struct csdev_access *csa)
> +{
> +	csdev_access_relaxed_write32(csa, CORESIGHT_CLAIM_SELF_HOSTED,
>   				     CORESIGHT_CLAIMCLR);
>   	isb();
>   }
> +EXPORT_SYMBOL_GPL(coresight_clear_self_claim_tag_unlocked);
>   
>   /*
>    * coresight_claim_device_unlocked : Claim the device for self-hosted usage
> @@ -180,7 +189,7 @@ int coresight_claim_device_unlocked(struct coresight_device *csdev)
>   	if (coresight_is_claimed_self_hosted(csdev))
>   		return 0;
>   	/* There was a race setting the tag, clean up and fail */
> -	coresight_clear_self_claim_tag(csdev);
> +	coresight_clear_self_claim_tag_unlocked(&csdev->access);
>   	return -EBUSY;
>   }
>   EXPORT_SYMBOL_GPL(coresight_claim_device_unlocked);
> @@ -211,7 +220,7 @@ void coresight_disclaim_device_unlocked(struct coresight_device *csdev)
>   		return;
>   
>   	if (coresight_is_claimed_self_hosted(csdev))
> -		coresight_clear_self_claim_tag(csdev);
> +		coresight_clear_self_claim_tag_unlocked(&csdev->access);
>   	else
>   		/*
>   		 * The external agent may have not honoured our claim
> diff --git a/include/linux/coresight.h b/include/linux/coresight.h
> index d79a242b271d..00134a80d358 100644
> --- a/include/linux/coresight.h
> +++ b/include/linux/coresight.h
> @@ -685,7 +685,8 @@ extern int coresight_timeout_action(struct csdev_access *csa, u32 offset,
>   
>   extern int coresight_claim_device(struct coresight_device *csdev);
>   extern int coresight_claim_device_unlocked(struct coresight_device *csdev);
> -
> +void coresight_clear_self_claim_tag(struct csdev_access *csa);
> +void coresight_clear_self_claim_tag_unlocked(struct csdev_access *csa);
>   extern void coresight_disclaim_device(struct coresight_device *csdev);
>   extern void coresight_disclaim_device_unlocked(struct coresight_device *csdev);
>   extern char *coresight_alloc_device_name(struct coresight_dev_list *devs,
>