[Intel-gfx] [PATCH v2] drm/i915: Add debugfs to read any DPCD register

[Jani Nikula]

On Wed, 08 Apr 2015, Durgadoss R <durgadoss.r at intel.com> wrote:
> This patch creates a connector specific debugfs
> interface to read any particular DPCD register.
> The DPCD register address (hex format) is written
> to 'i915_dpcd_addr' interface and the corresponding
> value can be read from 'i915_dpcd_val' interface.
>
> Example usage:
> echo 0x70 > i915_dpcd_addr
> cat i915_dpcd_val
> 0x1
>
> v2: Address Jani's comments.

So, code-wise this looks good to me.

But like I said in my review of v1, I am undecided on whether we want to
have this interface or not. I could really be persuaded either way.

Perhaps Ville or Paulo have an opinion?

BR,
Jani.


>
> Signed-off-by: Durgadoss R <durgadoss.r at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_debugfs.c | 88 ++++++++++++++++++++++++++++++++++++-
>  drivers/gpu/drm/i915/intel_drv.h    |  1 +
>  2 files changed, 88 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> index 10ca511..f1f365e 100644
> --- a/drivers/gpu/drm/i915/i915_debugfs.c
> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> @@ -4865,6 +4865,87 @@ static const struct file_operations i915_dpcd_fops = {
>  	.release = single_release,
>  };
>  
> +static ssize_t i915_dpcd_addr_write(struct file *file, const char __user *ubuf,
> +				     size_t len, loff_t *offp)
> +{
> +	struct seq_file *m = file->private_data;
> +	struct drm_connector *connector = m->private;
> +	struct intel_dp *intel_dp =
> +		enc_to_intel_dp(&intel_attached_encoder(connector)->base);
> +	unsigned int reg_addr;
> +	char tmp[16];
> +
> +	if (len >= sizeof(tmp))
> +		return -EINVAL;
> +
> +	if (copy_from_user(tmp, ubuf, len))
> +		return -EFAULT;
> +
> +	tmp[len] = '\0';
> +
> +	if (kstrtouint(tmp, 16, &reg_addr))
> +		return -EINVAL;
> +
> +	intel_dp->debugfs_dpcd_addr = reg_addr;
> +
> +	return len;
> +}
> +
> +static int i915_dpcd_addr_show(struct seq_file *m, void *data)
> +{
> +	struct drm_connector *connector = m->private;
> +	struct intel_dp *intel_dp =
> +		enc_to_intel_dp(&intel_attached_encoder(connector)->base);
> +
> +	seq_printf(m, "0x%x\n", intel_dp->debugfs_dpcd_addr);
> +
> +	return 0;
> +}
> +
> +static int i915_dpcd_addr_open(struct inode *inode, struct file *file)
> +{
> +	return single_open(file, i915_dpcd_addr_show, inode->i_private);
> +}
> +
> +static const struct file_operations i915_dpcd_addr_fops = {
> +	.owner = THIS_MODULE,
> +	.open = i915_dpcd_addr_open,
> +	.read = seq_read,
> +	.write = i915_dpcd_addr_write,
> +	.llseek = seq_lseek,
> +	.release = single_release,
> +};
> +
> +static int i915_dpcd_val_show(struct seq_file *m, void *data)
> +{
> +	struct drm_connector *connector = m->private;
> +	struct intel_dp *intel_dp =
> +		enc_to_intel_dp(&intel_attached_encoder(connector)->base);
> +	u8 val;
> +	int ret;
> +
> +	ret = drm_dp_dpcd_readb(&intel_dp->aux,
> +				intel_dp->debugfs_dpcd_addr, &val);
> +	if (ret < 0)
> +		return ret;
> +
> +	seq_printf(m, "0x%x\n", val);
> +	return 0;
> +}
> +
> +static int i915_dpcd_val_open(struct inode *inode, struct file *file)
> +{
> +	return single_open(file, i915_dpcd_val_show, inode->i_private);
> +}
> +
> +static const struct file_operations i915_dpcd_val_fops = {
> +	.owner = THIS_MODULE,
> +	.open = i915_dpcd_val_open,
> +	.read = seq_read,
> +	.llseek = seq_lseek,
> +	.release = single_release,
> +};
> +
>  /**
>   * i915_debugfs_connector_add - add i915 specific connector debugfs files
>   * @connector: pointer to a registered drm_connector
> @@ -4883,9 +4964,14 @@ int i915_debugfs_connector_add(struct drm_connector *connector)
>  		return -ENODEV;
>  
>  	if (connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort ||
> -	    connector->connector_type == DRM_MODE_CONNECTOR_eDP)
> +	    connector->connector_type == DRM_MODE_CONNECTOR_eDP) {
>  		debugfs_create_file("i915_dpcd", S_IRUGO, root, connector,
>  				    &i915_dpcd_fops);
> +		debugfs_create_file("i915_dpcd_addr", S_IRUGO | S_IWUSR,
> +				root, connector, &i915_dpcd_addr_fops);
> +		debugfs_create_file("i915_dpcd_val", S_IRUGO, root,
> +				connector, &i915_dpcd_val_fops);
> +	}
>  
>  	return 0;
>  }
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 4799b11..0594baa 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -642,6 +642,7 @@ struct intel_dp {
>  	unsigned long last_power_cycle;
>  	unsigned long last_power_on;
>  	unsigned long last_backlight_off;
> +	unsigned int debugfs_dpcd_addr;
>  
>  	struct notifier_block edp_notifier;
>  
> -- 
> 1.9.1
>

-- 
Jani Nikula, Intel Open Source Technology Center