On Mon, 05 Jul 2021, venkata.sai.patnana@xxxxxxxxx wrote:
> From: Patnana Venkata Sai <venkata.sai.patnana@xxxxxxxxx>
>
> [What]:
> This patch creates a per connector debugfs node to expose
> the Input and Compressed BPP.
>
> The same node can be used from userspace to force
> DSC to a certain BPP(all accepted values).
>
> [Why]:
> Useful to verify all supported/requested compression bpp's
> through IGT
>
> v2: Remove unnecessary logic (Jani)
> v3: Drop pipe bpp in debugfs node (Vandita)
> v4: Minor cleanups (Vandita)
> v5: Fix NULL pointer dereference
> v6: Fix dim tool checkpatch errors
> Release the lock before return (Vandita)
This is difficult to review because there is so much that should be
fixed in intel_display_debugfs.c in general and in this patch
specifically.
I think the first thing here is... have you actually tried this and
verified it works?
Just by reading the code, I don't think it is usable.
>
> Cc: Vandita Kulkarni <vandita.kulkarni@xxxxxxxxx>
> Cc: Navare Manasi D <manasi.d.navare@xxxxxxxxx>
> Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
> Signed-off-by: Anusha Srivatsa <anusha.srivatsa@xxxxxxxxx>
> Signed-off-by: Patnana Venkata Sai <venkata.sai.patnana@xxxxxxxxx>
> ---
> .../drm/i915/display/intel_display_debugfs.c | 106 +++++++++++++++++-
> .../drm/i915/display/intel_display_types.h | 1 +
> 2 files changed, 106 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_display_debugfs.c b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
> index af9e58619667d..daa4018224b83 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_debugfs.c
> +++ b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
> @@ -2389,6 +2389,103 @@ static const struct file_operations i915_dsc_fec_support_fops = {
> .write = i915_dsc_fec_support_write
> };
>
> +static int i915_dsc_bpp_support_show(struct seq_file *m, void *data)
> +{
> + struct drm_connector *connector = m->private;
General: I don't understand why we keep passing drm_connector instead of
intel_connector as private data.
> + struct drm_device *dev = connector->dev;
> + struct drm_crtc *crtc;
> + struct intel_crtc_state *crtc_state = NULL;
Unnecessary initialization.
> + struct intel_encoder *encoder = intel_attached_encoder(to_intel_connector(connector));
> + int ret = 0;
Unnecessary initialization.
> +
> + if (!encoder)
> + return -ENODEV;
> +
> + ret = drm_modeset_lock_single_interruptible(&dev->mode_config.connection_mutex);
> + if (ret)
> + return ret;
> +
> + crtc = connector->state->crtc;
> + if (connector->status != connector_status_connected || !crtc) {
> + drm_modeset_unlock(&dev->mode_config.connection_mutex);
> + return -ENODEV;
In general we use
ret = -ENODEV;
goto out;
with the unlock and other cleanup at the end, same unlock for both
success and fail paths. It's the prevalent style in kernel. Same all
over.
> + }
> +
> + crtc_state = to_intel_crtc_state(crtc->state);
> + seq_printf(m, "Compressed_BPP: %d\n", crtc_state->dsc.compressed_bpp);
> +
> + drm_modeset_unlock(&dev->mode_config.connection_mutex);
> +
> + return ret;
> +}
> +
> +static ssize_t i915_dsc_bpp_support_write(struct file *file,
> + const char __user *ubuf,
> + size_t len, loff_t *offp)
> +{
> + int dsc_bpp = 0;
> + int ret;
Usually the more "context" style variables go first.
> + struct drm_connector *connector =
> + ((struct seq_file *)file->private_data)->private;
> + struct intel_encoder *encoder = intel_attached_encoder(to_intel_connector(connector));
> + struct drm_i915_private *i915 = to_i915(encoder->base.dev);
> + struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
> + struct drm_crtc *crtc;
> + struct intel_crtc_state *crtc_state = NULL;
Unnecessary initialization.
> +
> + if (len == 0)
> + return 0;
Should be unnecessary.
> +
> + ret = kstrtoint_from_user(ubuf, len, 0, &dsc_bpp);
> + if (ret < 0)
> + return ret;
> +
> + ret = drm_modeset_lock_single_interruptible(&i915->drm.mode_config.connection_mutex);
> + if (ret)
> + return ret;
> +
> + crtc = connector->state->crtc;
> + if (connector->status != connector_status_connected || !crtc) {
> + drm_modeset_unlock(&i915->drm.mode_config.connection_mutex);
> + return -ENODEV;
Ditto here about failure path.
> + }
> +
> + crtc_state = to_intel_crtc_state(crtc->state);
> +
> + if (dsc_bpp <= 8 || dsc_bpp >= crtc_state->pipe_bpp) {
This is odd. In order to have crtc_state->pipe_bpp, or crtc state, you
must have done a modeset. That modeset must have been done without the
force_dsc_bpp. So in order to use this code, the test needs to:
- do a modeset
- set the force bpp
- do another modeset for the change to take effect
I don't think it makes sense to make that a requirement. Maybe we
shouldn't even require connector_status_connected. Just find intel_dp
and set ->force_dsc_bpp. Next modeset will use it. Have the value check
there.
This code also prevents you from resetting the force_dsc_bpp. If you set
it once, you can't set it back to 0 afterwards.
> + drm_modeset_unlock(&i915->drm.mode_config.connection_mutex);
> + drm_dbg(&i915->drm, "Compressed_BPP should be with in the limits\n");
> +
> + return -EINVAL;
> + }
> +
> + drm_modeset_unlock(&i915->drm.mode_config.connection_mutex);
> +
> + drm_dbg(&i915->drm,
> + "Copied %zu bytes from user to force BPP\n", len);
This is a completely useless debug message.
> +
> + intel_dp->force_dsc_bpp = dsc_bpp;
> + *offp += len;
> +
> + return len;
> +}
> +
> +static int i915_dsc_bpp_support_open(struct inode *inode,
> + struct file *file)
> +{
> + return single_open(file, i915_dsc_bpp_support_show,
> + inode->i_private);
> +}
> +
> +static const struct file_operations i915_dsc_bpp_support_fops = {
> + .owner = THIS_MODULE,
> + .open = i915_dsc_bpp_support_open,
> + .read = seq_read,
> + .llseek = seq_lseek,
> + .release = single_release,
> + .write = i915_dsc_bpp_support_write
> +};
Maybe this should use DEFINE_SEQ_ATTRIBUTE() to avoid some boilerplate.
> +
> /**
> * intel_connector_debugfs_add - add i915 specific connector debugfs files
> * @connector: pointer to a registered drm_connector
> @@ -2427,9 +2524,16 @@ int intel_connector_debugfs_add(struct drm_connector *connector)
> connector, &i915_hdcp_sink_capability_fops);
> }
>
> - if ((DISPLAY_VER(dev_priv) >= 11 || IS_CANNONLAKE(dev_priv)) && ((connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort && !to_intel_connector(connector)->mst_port) || connector->connector_type == DRM_MODE_CONNECTOR_eDP))
> + if ((DISPLAY_VER(dev_priv) >= 11 || IS_CANNONLAKE(dev_priv)) &&
> + ((connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort &&
> + !to_intel_connector(connector)->mst_port) ||
> + connector->connector_type == DRM_MODE_CONNECTOR_eDP)) {
> debugfs_create_file("i915_dsc_fec_support", S_IRUGO, root,
> connector, &i915_dsc_fec_support_fops);
> + debugfs_create_file("i915_dsc_bpp_support", 0444,
> + root, connector,
> + &i915_dsc_bpp_support_fops);
> + }
I don't understand how either i915_dsc_fec_support or
i915_dsc_bpp_support (which is an odd name for something to set an
integer value to!) can work if their mode is read-only 0444.
Has either been tested?
BR,
Jani.
>
> /* Legacy panels doesn't lpsp on any platform */
> if ((DISPLAY_VER(dev_priv) >= 9 || IS_HASWELL(dev_priv) ||
> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
> index d94f361b548b7..19d8d3eefbc27 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> @@ -1612,6 +1612,7 @@ struct intel_dp {
>
> /* Display stream compression testing */
> bool force_dsc_en;
> + int force_dsc_bpp;
>
> bool hobl_failed;
> bool hobl_active;
--
Jani Nikula, Intel Open Source Graphics Center
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