Re: [PATCH v2] drm/i915: Add debugfs to read any DPCD register

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Apr 16, 2015 at 05:07:00PM +0300, Jani Nikula wrote:
> On Wed, 08 Apr 2015, Durgadoss R <durgadoss.r@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?

I think having the ability to read (and also write actually) DPCD would
be nice.

So I like the idea, but it does seem a bit limited since it doesn't
allow writes. So perhaps we should just expose the entire DPCD as a
binary file and include a tool in i-g-t to read/write individual
pieces?

We could also have a tool to parse the entire thing like we have
for the vbt stuff.

> 
> BR,
> Jani.
> 
> 
> >
> > Signed-off-by: Durgadoss R <durgadoss.r@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
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Ville Syrjälä
Intel OTC
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