linux-kernel - Re: [PATCHv3] coresight: tmc: Add shutdown callback for TMC ETR

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Date:   Tue, 23 Jun 2020 11:25:32 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
Cc:     Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, Stephen Boyd <swboyd@...omium.org>
Subject: Re: [PATCHv3] coresight: tmc: Add shutdown callback for TMC ETR

On Tue, Jun 16, 2020 at 10:26:23AM +0530, Sai Prakash Ranjan wrote:
> Implement a shutdown callback to ensure ETR hardware is
> properly shutdown in reboot/shutdown path. This is required
> for ETR which has SMMU address translation enabled like on
> SC7180 SoC and few others. If the hardware is still accessing
> memory after SMMU translation is disabled as part of SMMU
> shutdown callback in system reboot or shutdown path, then
> IOVAs(I/O virtual address) which it was using will go on the
> bus as the physical addresses which might result in unknown
> crashes (NoC/interconnect errors). So we make sure from this
> shutdown callback that the ETR is shutdown before SMMU translation
> is disabled and device_link in SMMU driver will take care of
> ordering of shutdown callbacks such that SMMU shutdown callback
> is not called before any of its consumer shutdown callbacks.
> 
> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
> ---

I have applied your patch.

Thanks,
Mathieu

> 
> Changes since v2:
>  * Remove ETF/ETB disable as suggested by Mathieu and Mike since they are
>    not really affected.
>  * Remove coresight and misc device unregister since it is not required
>    for shutdown callback unlike remove callback and userspace is long gone
>    by this time.
> 
> Changes since v1:
>  * Use mode flag and drop enable flag as Mike suggested.
>  * Use spinlock before tmc hw disable as Mike suggested.
> 
> ---
>  .../hwtracing/coresight/coresight-tmc-etr.c   |  2 +-
>  drivers/hwtracing/coresight/coresight-tmc.c   | 23 +++++++++++++++++++
>  drivers/hwtracing/coresight/coresight-tmc.h   |  1 +
>  3 files changed, 25 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> index 625882bc8b08..b29c2db94d96 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> @@ -1110,7 +1110,7 @@ static void __tmc_etr_disable_hw(struct tmc_drvdata *drvdata)
>  
>  }
>  
> -static void tmc_etr_disable_hw(struct tmc_drvdata *drvdata)
> +void tmc_etr_disable_hw(struct tmc_drvdata *drvdata)
>  {
>  	__tmc_etr_disable_hw(drvdata);
>  	/* Disable CATU device if this ETR is connected to one */
> diff --git a/drivers/hwtracing/coresight/coresight-tmc.c b/drivers/hwtracing/coresight/coresight-tmc.c
> index 39fba1d16e6e..b13ce0daa572 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc.c
> @@ -538,6 +538,28 @@ static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
>  	return ret;
>  }
>  
> +static void tmc_shutdown(struct amba_device *adev)
> +{
> +	unsigned long flags;
> +	struct tmc_drvdata *drvdata = amba_get_drvdata(adev);
> +
> +	spin_lock_irqsave(&drvdata->spinlock, flags);
> +
> +	if (drvdata->mode == CS_MODE_DISABLED)
> +		goto out;
> +
> +	if (drvdata->config_type == TMC_CONFIG_TYPE_ETR)
> +		tmc_etr_disable_hw(drvdata);
> +
> +	/*
> +	 * We do not care about coresight unregister here unlike remove
> +	 * callback which is required for making coresight modular since
> +	 * the system is going down after this.
> +	 */
> +out:
> +	spin_unlock_irqrestore(&drvdata->spinlock, flags);
> +}
> +
>  static const struct amba_id tmc_ids[] = {
>  	CS_AMBA_ID(0x000bb961),
>  	/* Coresight SoC 600 TMC-ETR/ETS */
> @@ -556,6 +578,7 @@ static struct amba_driver tmc_driver = {
>  		.suppress_bind_attrs = true,
>  	},
>  	.probe		= tmc_probe,
> +	.shutdown	= tmc_shutdown,
>  	.id_table	= tmc_ids,
>  };
>  builtin_amba_driver(tmc_driver);
> diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h
> index 71de978575f3..6e8d2dc33d17 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc.h
> +++ b/drivers/hwtracing/coresight/coresight-tmc.h
> @@ -268,6 +268,7 @@ ssize_t tmc_etb_get_sysfs_trace(struct tmc_drvdata *drvdata,
>  /* ETR functions */
>  int tmc_read_prepare_etr(struct tmc_drvdata *drvdata);
>  int tmc_read_unprepare_etr(struct tmc_drvdata *drvdata);
> +void tmc_etr_disable_hw(struct tmc_drvdata *drvdata);
>  extern const struct coresight_ops tmc_etr_cs_ops;
>  ssize_t tmc_etr_get_sysfs_trace(struct tmc_drvdata *drvdata,
>  				loff_t pos, size_t len, char **bufpp);
> 
> base-commit: 059e38815950dbec65beafe03757bce9436e89a4
> -- 
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
> of Code Aurora Forum, hosted by The Linux Foundation
>