linux-kernel - Re: [RFC PATCH 03/14] coresight: tpiu: Use coresight device access abstraction

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Message-ID: <20200729210105.GC3073178@xps15>
Date:   Wed, 29 Jul 2020 15:01:05 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        mike.leach@...aro.org, coresight@...ts.linaro.org
Subject: Re: [RFC PATCH 03/14] coresight: tpiu: Use coresight device access
 abstraction

On Wed, Jul 22, 2020 at 06:20:29PM +0100, Suzuki K Poulose wrote:
> TPIU driver access the device before the coresight device
> is registered. In other words, before the drvdata->csdev
> is valid. Thus, we need to make sure that the csdev_access
> is valid for both the invocations. Switch to using the
> csdev_access directly instead of relying on availability
> of drvdata->csdev.

I'm not sure all of the above is needed and based on the wording I could easily
see this patch being selected for stable backport, which would be a mistak. 

The gist of this patch is that we are moving to the access abstraction and the
changelog should reflect that.

> 
> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> Cc: Mike Leach <mike.leach@...aro.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> ---
>  drivers/hwtracing/coresight/coresight-tpiu.c | 30 +++++++++-----------
>  1 file changed, 13 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-tpiu.c b/drivers/hwtracing/coresight/coresight-tpiu.c
> index 7ef7649f48ad..84ff4bf5d3b8 100644
> --- a/drivers/hwtracing/coresight/coresight-tpiu.c
> +++ b/drivers/hwtracing/coresight/coresight-tpiu.c
> @@ -60,49 +60,45 @@ struct tpiu_drvdata {
>  	struct coresight_device	*csdev;
>  };
>  
> -static void tpiu_enable_hw(struct tpiu_drvdata *drvdata)
> +static void tpiu_enable_hw(struct csdev_access *csa)
>  {
> -	CS_UNLOCK(drvdata->base);
> +	CS_UNLOCK(csa->base);
>  
>  	/* TODO: fill this up */
>  
> -	CS_LOCK(drvdata->base);
> +	CS_LOCK(csa->base);
>  }
>  
>  static int tpiu_enable(struct coresight_device *csdev, u32 mode, void *__unused)
>  {
> -	struct tpiu_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> -
> -	tpiu_enable_hw(drvdata);
> +	tpiu_enable_hw(&csdev->access);
>  	atomic_inc(csdev->refcnt);
>  	dev_dbg(&csdev->dev, "TPIU enabled\n");
>  	return 0;
>  }
>  
> -static void tpiu_disable_hw(struct tpiu_drvdata *drvdata)
> +static void tpiu_disable_hw(struct csdev_access *csa)
>  {
> -	CS_UNLOCK(drvdata->base);
> +	CS_UNLOCK(csa->base);
>  
>  	/* Clear formatter and stop on flush */
> -	writel_relaxed(FFCR_STOP_FI, drvdata->base + TPIU_FFCR);
> +	csdev_access_relaxed_write32(csa, FFCR_STOP_FI, TPIU_FFCR);
>  	/* Generate manual flush */
> -	writel_relaxed(FFCR_STOP_FI | FFCR_FON_MAN, drvdata->base + TPIU_FFCR);
> +	csdev_access_relaxed_write32(csa, FFCR_STOP_FI | FFCR_FON_MAN, TPIU_FFCR);
>  	/* Wait for flush to complete */
> -	coresight_timeout(drvdata->base, TPIU_FFCR, FFCR_FON_MAN_BIT, 0);
> +	coresight_timeout(csa->base, TPIU_FFCR, FFCR_FON_MAN_BIT, 0);
>  	/* Wait for formatter to stop */
> -	coresight_timeout(drvdata->base, TPIU_FFSR, FFSR_FT_STOPPED_BIT, 1);
> +	coresight_timeout(csa->base, TPIU_FFSR, FFSR_FT_STOPPED_BIT, 1);
>  
> -	CS_LOCK(drvdata->base);
> +	CS_LOCK(csa->base);
>  }
>  
>  static int tpiu_disable(struct coresight_device *csdev)
>  {
> -	struct tpiu_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> -
>  	if (atomic_dec_return(csdev->refcnt))
>  		return -EBUSY;
>  
> -	tpiu_disable_hw(drvdata);
> +	tpiu_disable_hw(&csdev->access);
>  
>  	dev_dbg(&csdev->dev, "TPIU disabled\n");
>  	return 0;
> @@ -152,7 +148,7 @@ static int tpiu_probe(struct amba_device *adev, const struct amba_id *id)
>  	desc.access.base = base;

Any reason for introducing the above in patch 02?  I would have done that as
part of this patch...  Also part of this patch I would remove drvdata::base
since it is no longer needed.

I'm out of time for today - I will continue tomorrow.

Regards,
Mathieu

>  
>  	/* Disable tpiu to support older devices */
> -	tpiu_disable_hw(drvdata);
> +	tpiu_disable_hw(&desc.access);
>  
>  	pdata = coresight_get_platform_data(dev);
>  	if (IS_ERR(pdata))
> -- 
> 2.24.1
>