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

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

On Fri, Apr 17, 2015 at 06:33:57AM +0000, R, Durgadoss wrote:
> >-----Original Message-----
> >From: Ville Syrjälä [mailto:ville.syrjala@linux.intel.com]
> >Sent: Thursday, April 16, 2015 8:03 PM
> >To: Jani Nikula
> >Cc: R, Durgadoss; intel-gfx@lists.freedesktop.org; Syrjala, Ville; Zanoni, Paulo R
> >Subject: Re: [Intel-gfx] [PATCH v2] drm/i915: Add debugfs to read any DPCD register
> >
> >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.
> 
> Yes, This seems to be a good idea. I will start working on this.
> Although I am not sure on the 'write' part.. I guess we can discuss
> as we go along..
> 
> But I still think, a pointed read/write would also be useful
> at times for debug. So, If you agree, I can extend this interface
> to take values for write as well and submit a v3.

For me at least i-g-t is always around so if a small tool is needed
to make the read/write a single register case easy, I'm fine with
that. We anyway need tools to read/write everything else, so I don't
see a big difference here. But if other people would prefer something
that doesn't need a specific tool I won't object to it either.

> 
> Thanks,
> Durga
> 
> >
> >>
> >> 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

-- 
Ville Syrjälä
Intel OTC
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