Re: [PATCH] drm/i915: Add debugfs hooks for messign with watermark latencies

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

On Wed, Jan 22, 2014 at 02:26:26PM +0000, Damien Lespiau wrote:
> On Wed, Jan 22, 2014 at 02:36:08PM +0200, ville.syrjala@linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > Add a few new debugfs files which allow changing the watermark memory
> > latency values during runtime. This can be used to determine the if the
> > original BIOS provided latency values are no good.
> > 
> > v2: Drop superfluous plane name from output
> >     Take modeset locks around the latency value read/write
> 
> Huum, I was thinking that it may be practical to write the latencies in
> usec instead of the level dependent (and potentially platform dependent)
> units. It can also be done in the small helper from user space anyway.

Yeah I'm not really convinced I've designed this interface properly. I
also slightly dislike the fact that the input and output formats aren't
the same. So I was wondering if I should just change the output format
to match the non decorated input format, and then leave it up to the
userspace to make it look nicer. But it's debugfs so I'm not too worried
about the longevity of the design.

> 
> Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
> 
> -- 
> Damien
> 
> > 
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_debugfs.c | 171 ++++++++++++++++++++++++++++++++++++
> >  1 file changed, 171 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> > index 473dda2..6fbac11 100644
> > --- a/drivers/gpu/drm/i915/i915_debugfs.c
> > +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> > @@ -2784,6 +2784,174 @@ static const struct file_operations i915_display_crc_ctl_fops = {
> >  	.write = display_crc_ctl_write
> >  };
> >  
> > +static void wm_latency_show(struct seq_file *m, const uint16_t wm[5])
> > +{
> > +	struct drm_device *dev = m->private;
> > +	int num_levels = IS_HASWELL(dev) || IS_BROADWELL(dev) ? 5 : 4;
> > +	int level;
> > +
> > +	drm_modeset_lock_all(dev);
> > +
> > +	for (level = 0; level < num_levels; level++) {
> > +		unsigned int latency = wm[level];
> > +
> > +		/* WM1+ latency values in 0.5us units */
> > +		if (level > 0)
> > +			latency *= 5;
> > +
> > +		seq_printf(m, "WM%d %u (%u.%u usec)\n",
> > +			   level, wm[level],
> > +			   latency / 10, latency % 10);
> > +	}
> > +
> > +	drm_modeset_unlock_all(dev);
> > +}
> > +
> > +static int pri_wm_latency_show(struct seq_file *m, void *data)
> > +{
> > +	struct drm_device *dev = m->private;
> > +
> > +	wm_latency_show(m, to_i915(dev)->wm.pri_latency);
> > +
> > +	return 0;
> > +}
> > +
> > +static int spr_wm_latency_show(struct seq_file *m, void *data)
> > +{
> > +	struct drm_device *dev = m->private;
> > +
> > +	wm_latency_show(m, to_i915(dev)->wm.spr_latency);
> > +
> > +	return 0;
> > +}
> > +
> > +static int cur_wm_latency_show(struct seq_file *m, void *data)
> > +{
> > +	struct drm_device *dev = m->private;
> > +
> > +	wm_latency_show(m, to_i915(dev)->wm.cur_latency);
> > +
> > +	return 0;
> > +}
> > +
> > +static int pri_wm_latency_open(struct inode *inode, struct file *file)
> > +{
> > +	struct drm_device *dev = inode->i_private;
> > +
> > +	if (!HAS_PCH_SPLIT(dev))
> > +		return -ENODEV;
> > +
> > +	return single_open(file, pri_wm_latency_show, dev);
> > +}
> > +
> > +static int spr_wm_latency_open(struct inode *inode, struct file *file)
> > +{
> > +	struct drm_device *dev = inode->i_private;
> > +
> > +	if (!HAS_PCH_SPLIT(dev))
> > +		return -ENODEV;
> > +
> > +	return single_open(file, spr_wm_latency_show, dev);
> > +}
> > +
> > +static int cur_wm_latency_open(struct inode *inode, struct file *file)
> > +{
> > +	struct drm_device *dev = inode->i_private;
> > +
> > +	if (!HAS_PCH_SPLIT(dev))
> > +		return -ENODEV;
> > +
> > +	return single_open(file, cur_wm_latency_show, dev);
> > +}
> > +
> > +static ssize_t wm_latency_write(struct file *file, const char __user *ubuf,
> > +				size_t len, loff_t *offp, uint16_t wm[5])
> > +{
> > +	struct seq_file *m = file->private_data;
> > +	struct drm_device *dev = m->private;
> > +	uint16_t new[5] = { 0 };
> > +	int num_levels = IS_HASWELL(dev) || IS_BROADWELL(dev) ? 5 : 4;
> > +	int level;
> > +	int ret;
> > +	char tmp[32];
> > +
> > +	if (len >= sizeof(tmp))
> > +		return -EINVAL;
> > +
> > +	if (copy_from_user(tmp, ubuf, len))
> > +		return -EFAULT;
> > +
> > +	tmp[len] = '\0';
> > +
> > +	ret = sscanf(tmp, "%hu %hu %hu %hu %hu", &new[0], &new[1], &new[2], &new[3], &new[4]);
> > +	if (ret != num_levels)
> > +		return -EINVAL;
> > +
> > +	drm_modeset_lock_all(dev);
> > +
> > +	for (level = 0; level < num_levels; level++)
> > +		wm[level] = new[level];
> > +
> > +	drm_modeset_unlock_all(dev);
> > +
> > +	return len;
> > +}
> > +
> > +
> > +static ssize_t pri_wm_latency_write(struct file *file, const char __user *ubuf,
> > +				    size_t len, loff_t *offp)
> > +{
> > +	struct seq_file *m = file->private_data;
> > +	struct drm_device *dev = m->private;
> > +
> > +	return wm_latency_write(file, ubuf, len, offp, to_i915(dev)->wm.pri_latency);
> > +}
> > +
> > +static ssize_t spr_wm_latency_write(struct file *file, const char __user *ubuf,
> > +				    size_t len, loff_t *offp)
> > +{
> > +	struct seq_file *m = file->private_data;
> > +	struct drm_device *dev = m->private;
> > +
> > +	return wm_latency_write(file, ubuf, len, offp, to_i915(dev)->wm.spr_latency);
> > +}
> > +
> > +static ssize_t cur_wm_latency_write(struct file *file, const char __user *ubuf,
> > +				    size_t len, loff_t *offp)
> > +{
> > +	struct seq_file *m = file->private_data;
> > +	struct drm_device *dev = m->private;
> > +
> > +	return wm_latency_write(file, ubuf, len, offp, to_i915(dev)->wm.cur_latency);
> > +}
> > +
> > +static const struct file_operations i915_pri_wm_latency_fops = {
> > +	.owner = THIS_MODULE,
> > +	.open = pri_wm_latency_open,
> > +	.read = seq_read,
> > +	.llseek = seq_lseek,
> > +	.release = single_release,
> > +	.write = pri_wm_latency_write
> > +};
> > +
> > +static const struct file_operations i915_spr_wm_latency_fops = {
> > +	.owner = THIS_MODULE,
> > +	.open = spr_wm_latency_open,
> > +	.read = seq_read,
> > +	.llseek = seq_lseek,
> > +	.release = single_release,
> > +	.write = spr_wm_latency_write
> > +};
> > +
> > +static const struct file_operations i915_cur_wm_latency_fops = {
> > +	.owner = THIS_MODULE,
> > +	.open = cur_wm_latency_open,
> > +	.read = seq_read,
> > +	.llseek = seq_lseek,
> > +	.release = single_release,
> > +	.write = cur_wm_latency_write
> > +};
> > +
> >  static int
> >  i915_wedged_get(void *data, u64 *val)
> >  {
> > @@ -3297,6 +3465,9 @@ static const struct i915_debugfs_files {
> >  	{"i915_error_state", &i915_error_state_fops},
> >  	{"i915_next_seqno", &i915_next_seqno_fops},
> >  	{"i915_display_crc_ctl", &i915_display_crc_ctl_fops},
> > +	{"i915_pri_wm_latency", &i915_pri_wm_latency_fops},
> > +	{"i915_spr_wm_latency", &i915_spr_wm_latency_fops},
> > +	{"i915_cur_wm_latency", &i915_cur_wm_latency_fops},
> >  };
> >  
> >  void intel_display_crc_init(struct drm_device *dev)
> > -- 
> > 1.8.3.2
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Ville Syrjälä
Intel OTC