linux-kernel - Re: [PATCH v2 15/16] dmaengine: bcm-sba-raid: Add debugfs support

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Date:   Thu, 17 Aug 2017 13:31:43 +0530
From:   Vinod Koul <vinod.koul@...el.com>
To:     Anup Patel <anup.patel@...adcom.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Dan Williams <dan.j.williams@...el.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Scott Branden <sbranden@...adcom.com>,
        Ray Jui <rjui@...adcom.com>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        dmaengine@...r.kernel.org, bcm-kernel-feedback-list@...adcom.com
Subject: Re: [PATCH v2 15/16] dmaengine: bcm-sba-raid: Add debugfs support

On Tue, Aug 01, 2017 at 04:07:59PM +0530, Anup Patel wrote:
> This patch adds debugfs support to report stats via debugfs
> which in-turn will help debug hang or error situations.
> 
> Signed-off-by: Anup Patel <anup.patel@...adcom.com>
> Reviewed-by: Ray Jui <ray.jui@...adcom.com>
> Reviewed-by: Scott Branden <scott.branden@...adcom.com>
> ---
>  drivers/dma/bcm-sba-raid.c | 82 +++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 81 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/dma/bcm-sba-raid.c b/drivers/dma/bcm-sba-raid.c
> index f0a0e80..f9d110c 100644
> --- a/drivers/dma/bcm-sba-raid.c
> +++ b/drivers/dma/bcm-sba-raid.c
> @@ -36,6 +36,7 @@
>   */
>  
>  #include <linux/bitops.h>
> +#include <linux/debugfs.h>
>  #include <linux/dma-mapping.h>
>  #include <linux/dmaengine.h>
>  #include <linux/list.h>
> @@ -162,6 +163,9 @@ struct sba_device {
>  	struct list_head reqs_completed_list;
>  	struct list_head reqs_aborted_list;
>  	struct list_head reqs_free_list;
> +	/* DebugFS directory entries */
> +	struct dentry *root;
> +	struct dentry *stats;
>  };
>  
>  /* ====== Command helper routines ===== */
> @@ -486,6 +490,45 @@ static void sba_process_received_request(struct sba_device *sba,
>  	}
>  }
>  
> +static void sba_write_stats_in_seqfile(struct sba_device *sba,
> +				       struct seq_file *file)
> +{
> +	unsigned long flags;
> +	struct sba_request *req;
> +	u32 free_count = 0, alloced_count = 0, pending_count = 0;
> +	u32 active_count = 0, aborted_count = 0, completed_count = 0;
> +
> +	spin_lock_irqsave(&sba->reqs_lock, flags);
> +
> +	list_for_each_entry(req, &sba->reqs_free_list, node)
> +		free_count++;
> +
> +	list_for_each_entry(req, &sba->reqs_alloc_list, node)
> +		alloced_count++;
> +
> +	list_for_each_entry(req, &sba->reqs_pending_list, node)
> +		pending_count++;
> +
> +	list_for_each_entry(req, &sba->reqs_active_list, node)
> +		active_count++;
> +
> +	list_for_each_entry(req, &sba->reqs_aborted_list, node)
> +		aborted_count++;
> +
> +	list_for_each_entry(req, &sba->reqs_completed_list, node)
> +		completed_count++;
> +
> +	spin_unlock_irqrestore(&sba->reqs_lock, flags);
> +
> +	seq_printf(file, "maximum requests   = %d\n", sba->max_req);
> +	seq_printf(file, "free requests      = %d\n", free_count);
> +	seq_printf(file, "alloced requests   = %d\n", alloced_count);
> +	seq_printf(file, "pending requests   = %d\n", pending_count);
> +	seq_printf(file, "active requests    = %d\n", active_count);
> +	seq_printf(file, "aborted requests   = %d\n", aborted_count);
> +	seq_printf(file, "completed requests = %d\n", completed_count);
> +}
> +
>  /* ====== DMAENGINE callbacks ===== */
>  
>  static void sba_free_chan_resources(struct dma_chan *dchan)
> @@ -1451,6 +1494,19 @@ static void sba_receive_message(struct mbox_client *cl, void *msg)
>  	sba_process_received_request(sba, req);
>  }
>  
> +/* ====== Debugfs callbacks ====== */
> +
> +static int sba_debugfs_stats_show(struct seq_file *file, void *offset)
> +{
> +	struct platform_device *pdev = to_platform_device(file->private);
> +	struct sba_device *sba = platform_get_drvdata(pdev);
> +
> +	/* Write stats in file */
> +	sba_write_stats_in_seqfile(sba, file);
> +
> +	return 0;
> +}
> +
>  /* ====== Platform driver routines ===== */
>  
>  static int sba_prealloc_channel_resources(struct sba_device *sba)
> @@ -1721,10 +1777,30 @@ static int sba_probe(struct platform_device *pdev)
>  	if (ret)
>  		goto fail_free_mchans;
>  
> +	/* Check availability of debugfs */
> +	if (!debugfs_initialized())
> +		goto skip_debugfs;
> +
> +	/* Create debugfs root entry */
> +	sba->root = debugfs_create_dir(dev_name(sba->dev), NULL);
> +	if (IS_ERR_OR_NULL(sba->root)) {
> +		ret = PTR_ERR_OR_ZERO(sba->root);
> +		goto fail_free_resources;

why fail, debugfs should be an optional thingy, why would you want to fail here?

-- 
~Vinod