linux-kernel - Re: [PATCH v8 5/7] coresight: tmc: Add support for reading crash data

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Message-ID: <5fbb37f4-031b-4b8a-be7e-676cab82b180@arm.com>
Date: Fri, 31 May 2024 11:03:25 +0100
From: James Clark <james.clark@....com>
To: Linu Cherian <lcherian@...vell.com>
Cc: linux-arm-kernel@...ts.infradead.org, coresight@...ts.linaro.org,
 linux-kernel@...r.kernel.org, robh+dt@...nel.org,
 krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
 devicetree@...r.kernel.org, sgoutham@...vell.com, gcherian@...vell.com,
 Anil Kumar Reddy <areddy3@...vell.com>, Tanmay Jagdale <tanmay@...vell.com>,
 suzuki.poulose@....com, mike.leach@...aro.org
Subject: Re: [PATCH v8 5/7] coresight: tmc: Add support for reading crash data



On 31/05/2024 05:27, Linu Cherian wrote:
> * Introduce a new mode CS_MODE_READ_CRASHDATA for reading trace
>   captured in previous crash/watchdog reset.
> 
> * Add special device files for reading ETR/ETF crash data.
> 
> * User can read the crash data as below
> 
>   For example, for reading crash data from tmc_etf sink
> 
>   #dd if=/dev/crash_tmc_etfXX of=~/cstrace.bin
> 
> Signed-off-by: Anil Kumar Reddy <areddy3@...vell.com>
> Signed-off-by: Tanmay Jagdale <tanmay@...vell.com>
> Signed-off-by: Linu Cherian <lcherian@...vell.com>
> ---
> Changelog from v7:
> * Moved crash dev registration into new function,
>   register_crash_dev_interface
> * Removed redundant variable trace_addr in
>   tmc_etr_setup_crashdata_buf
> 
>  .../coresight/coresight-etm4x-core.c          |   1 +
>  .../hwtracing/coresight/coresight-tmc-core.c  | 148 ++++++++++++++++-
>  .../hwtracing/coresight/coresight-tmc-etf.c   |  73 +++++++++
>  .../hwtracing/coresight/coresight-tmc-etr.c   | 152 +++++++++++++++++-
>  drivers/hwtracing/coresight/coresight-tmc.h   |  11 +-
>  include/linux/coresight.h                     |  13 ++
>  6 files changed, 391 insertions(+), 7 deletions(-)
> 

[...]

> +static void register_crash_dev_interface(struct tmc_drvdata * drvdata,
> +					 const char *name)
> +{
> +	drvdata->crashdev.name =
> +		devm_kasprintf(&drvdata->csdev->dev, GFP_KERNEL, "%s_%s", "crash", name);
> +	drvdata->crashdev.minor = MISC_DYNAMIC_MINOR;
> +	drvdata->crashdev.fops = &tmc_crashdata_fops;
> +	if (misc_register(&drvdata->crashdev))
> +		dev_dbg(&drvdata->csdev->dev,
> +			"Failed to setup user interface for crashdata\n");
> +}
> +
>  static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
>  {
>  	int ret = 0;
> @@ -619,6 +752,10 @@ static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
>  		coresight_unregister(drvdata->csdev);
>  	else
>  		pm_runtime_put(&adev->dev);
> +
> +	if (is_tmc_reserved_region_valid(dev))
> +		register_crash_dev_interface(drvdata, desc.name);
> +

Now that you've added an extra step to the probe you need to add a "goto
out" when the previous step fails:

  if (ret) {
	coresight_unregister(drvdata->csdev);
+	goto out;
  }

That seems to be the pattern in the rest of the function. Otherwise you
might register the interface on no device.

There's also a conflict here and in some other places. Since this has to
go through the coresight branch you should base it off of coresight-next.

>  out:
>  	return ret;
>  }
> @@ -630,7 +767,8 @@ static void tmc_shutdown(struct amba_device *adev)
>  
>  	spin_lock_irqsave(&drvdata->spinlock, flags);
>  
> -	if (coresight_get_mode(drvdata->csdev) == CS_MODE_DISABLED)
> +	if ((coresight_get_mode(drvdata->csdev) == CS_MODE_DISABLED) ||
> +	    (coresight_get_mode(drvdata->csdev) == CS_MODE_READ_CRASHDATA))
>  		goto out;
>  
>  	if (drvdata->config_type == TMC_CONFIG_TYPE_ETR)
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> index f9569585e9f8..655c0c0ba54b 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> @@ -657,6 +657,56 @@ static int tmc_panic_sync_etf(struct coresight_device *csdev)
>  	return 0;
>  }
>  

[...]

> @@ -725,6 +789,7 @@ int tmc_read_prepare_etb(struct tmc_drvdata *drvdata)
>  		__tmc_etb_disable_hw(drvdata);
>  	}
>  
> +mode_valid:
>  	drvdata->reading = true;
>  out:
>  	spin_unlock_irqrestore(&drvdata->spinlock, flags);
> @@ -744,8 +809,16 @@ int tmc_read_unprepare_etb(struct tmc_drvdata *drvdata)
>  			 drvdata->config_type != TMC_CONFIG_TYPE_ETF))
>  		return -EINVAL;
>  
> +

Whitespace change. There are a couple of other minor checkpatch style
warnings.

The rest looks good to me. All the tests are passing. I still think we
should all the kself test for this mode, but that can be done later.