linux-kernel - Re: [PATCH v3 1/7] coresight: Convert tag clear function to take a struct cs

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Message-ID: <3bbf8aee-7b84-405a-8a3f-648c74196c2c@arm.com>
Date: Fri, 21 Mar 2025 11:02:02 +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 v3 1/7] coresight: Convert tag clear function to take a
 struct cs_access

On 20/03/2025 14:34, 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.
> 
> These look functions look like they set the whole tags register as one
> value, but they only set and clear the self hosted bit using a SET/CLR
> bits mechanism so also rename the functions to reflect this better.
> 
> Reviewed-by: Leo Yan <leo.yan@....com>
> Signed-off-by: James Clark <james.clark@...aro.org>
> ---
>   drivers/hwtracing/coresight/coresight-core.c | 27 +++++++++++++++++++--------
>   include/linux/coresight.h                    |  3 ++-
>   2 files changed, 21 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
> index fb43ef6a3b1f..8471aefeac76 100644
> --- a/drivers/hwtracing/coresight/coresight-core.c
> +++ b/drivers/hwtracing/coresight/coresight-core.c
> @@ -144,19 +144,30 @@ static inline bool coresight_is_claimed_any(struct coresight_device *csdev)
>   	return coresight_read_claim_tags(csdev) != 0;
>   }
>   
> -static inline void coresight_set_claim_tags(struct coresight_device *csdev)
> +static inline void coresight_set_self_claim_tag(struct coresight_device *csdev)

nit: For consistency, this should be renamed to _unlocked ?

Rest looks fine to me

Suzuki


>   {
>   	csdev_access_relaxed_write32(&csdev->access, CORESIGHT_CLAIM_SELF_HOSTED,
>   				     CORESIGHT_CLAIMSET);
>   	isb();
>   }
>   
> -static inline void coresight_clear_claim_tags(struct coresight_device *csdev)
> +void coresight_clear_self_claim_tag(struct csdev_access *csa)
>   {
> -	csdev_access_relaxed_write32(&csdev->access, CORESIGHT_CLAIM_SELF_HOSTED,
> +	if (csa->io_mem)
> +		CS_UNLOCK(csa->base);
> +	coresight_clear_self_claim_tag_unlocked(csa);
> +	if (csa->io_mem)
> +		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
> @@ -176,11 +187,11 @@ int coresight_claim_device_unlocked(struct coresight_device *csdev)
>   	if (coresight_is_claimed_any(csdev))
>   		return -EBUSY;
>   
> -	coresight_set_claim_tags(csdev);
> +	coresight_set_self_claim_tag(csdev);
>   	if (coresight_is_claimed_self_hosted(csdev))
>   		return 0;
> -	/* There was a race setting the tags, clean up and fail */
> -	coresight_clear_claim_tags(csdev);
> +	/* There was a race setting the tag, clean up and fail */
> +	coresight_clear_self_claim_tag_unlocked(&csdev->access);
>   	return -EBUSY;
>   }
>   EXPORT_SYMBOL_GPL(coresight_claim_device_unlocked);
> @@ -201,7 +212,7 @@ int coresight_claim_device(struct coresight_device *csdev)
>   EXPORT_SYMBOL_GPL(coresight_claim_device);
>   
>   /*
> - * coresight_disclaim_device_unlocked : Clear the claim tags for the device.
> + * coresight_disclaim_device_unlocked : Clear the claim tag for the device.
>    * Called with CS_UNLOCKed for the component.
>    */
>   void coresight_disclaim_device_unlocked(struct coresight_device *csdev)
> @@ -211,7 +222,7 @@ void coresight_disclaim_device_unlocked(struct coresight_device *csdev)
>   		return;
>   
>   	if (coresight_is_claimed_self_hosted(csdev))
> -		coresight_clear_claim_tags(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,
>