linux-kernel - Re: [PATCH v2 2/5] soundwire: cadence_master: add hw

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Date:   Mon, 21 Oct 2019 09:34:58 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        tiwai@...e.de, broonie@...nel.org, gregkh@...uxfoundation.org,
        jank@...ence.com, srinivas.kandagatla@...aro.org,
        slawomir.blauciak@...el.com,
        Bard liao <yung-chuan.liao@...ux.intel.com>,
        Rander Wang <rander.wang@...ux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Sanyog Kale <sanyog.r.kale@...el.com>
Subject: Re: [PATCH v2 2/5] soundwire: cadence_master: add hw_reset
 capability in debugfs

On 16-09-19, 14:09, Pierre-Louis Bossart wrote:
> Provide debugfs capability to kick link and devices into hard-reset
> (as defined by MIPI). This capability is really useful when some
> devices are no longer responsive and/or to check the software handling
> of resynchronization.
> 
> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
> ---
>  drivers/soundwire/cadence_master.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/drivers/soundwire/cadence_master.c b/drivers/soundwire/cadence_master.c
> index e3d06330d125..5f900cf2acb9 100644
> --- a/drivers/soundwire/cadence_master.c
> +++ b/drivers/soundwire/cadence_master.c
> @@ -340,6 +340,23 @@ static int cdns_reg_show(struct seq_file *s, void *data)
>  }
>  DEFINE_SHOW_ATTRIBUTE(cdns_reg);
>  
> +static int cdns_hw_reset(void *data, u64 value)
> +{
> +	struct sdw_cdns *cdns = data;
> +	int ret;
> +
> +	if (value != 1)
> +		return -EINVAL;
> +
> +	ret = sdw_cdns_exit_reset(cdns);

So we are performing reset of the device behind the kernel, so I think
it makes sense to mark the kernel as tainted.

> +
> +	dev_dbg(cdns->dev, "link hw_reset done: %d\n", ret);
> +
> +	return ret;

We may want to get rid of the debug and do:
        return sdw_cdns_exit_reset();


> +}
> +
> +DEFINE_DEBUGFS_ATTRIBUTE(cdns_hw_reset_fops, NULL, cdns_hw_reset, "%llu\n");
> +
>  /**
>   * sdw_cdns_debugfs_init() - Cadence debugfs init
>   * @cdns: Cadence instance
> @@ -348,6 +365,9 @@ DEFINE_SHOW_ATTRIBUTE(cdns_reg);
>  void sdw_cdns_debugfs_init(struct sdw_cdns *cdns, struct dentry *root)
>  {
>  	debugfs_create_file("cdns-registers", 0400, root, cdns, &cdns_reg_fops);
> +
> +	debugfs_create_file("cdns-hw-reset", 0200, root, cdns,
> +			    &cdns_hw_reset_fops);
>  }
>  EXPORT_SYMBOL_GPL(sdw_cdns_debugfs_init);
>  
> -- 
> 2.20.1

-- 
~Vinod