Re: [PATCH] drm/i915: add i915 specific connector debugfs file for DPCD

[Todd Previte <tprevite@gmail.com>]

On 2/25/2015 5:34 AM, Jani Nikula wrote:
> Occasionally it would be interesting to read some of the DPCD registers
> for debug purposes, without having to resort to logging. Add an i915
> specific i915_dpcd debugfs file for DP and eDP connectors to dump parts
> of the DPCD. Currently the DPCD addresses to be dumped are statically
> configured, and more can be added trivially.
>
> The implementation also makes it relatively easy to add other i915 and
> connector specific debugfs files in the future, as necessary.
>
> This is currently i915 specific just because there's no generic way to
> do AUX transactions given just a drm_connector. However it's all pretty
> straightforward to port to other drivers.
>
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> ---
>   drivers/gpu/drm/i915/i915_debugfs.c | 93 +++++++++++++++++++++++++++++++++++++
>   drivers/gpu/drm/i915/i915_drv.h     |  1 +
>   drivers/gpu/drm/i915/intel_dp.c     |  2 +
>   3 files changed, 96 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> index 26e9c7b34113..451ef456c25f 100644
> --- a/drivers/gpu/drm/i915/i915_debugfs.c
> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> @@ -4652,3 +4652,96 @@ void i915_debugfs_cleanup(struct drm_minor *minor)
>   		drm_debugfs_remove_files(info_list, 1, minor);
>   	}
>   }
> +
> +struct dpcd_block {
> +	/* DPCD dump start address. */
> +	unsigned int offset;
> +	/* DPCD dump end address, inclusive. If unset, .size will be used. */
> +	unsigned int end;
> +	/* DPCD dump size. Used if .end is unset. If unset, defaults to 1. */
> +	size_t size;
> +	/* Only valid for eDP. */
> +	bool edp;
> +};
> +
> +static const struct dpcd_block i915_dpcd_debug[] = {
> +	{ .offset = DP_DPCD_REV, .size = DP_RECEIVER_CAP_SIZE },
> +	{ .offset = DP_PSR_SUPPORT, .end = DP_PSR_CAPS },
> +	{ .offset = DP_DOWNSTREAM_PORT_0, .size = 16 },
> +	{ .offset = DP_LINK_BW_SET, .end = DP_EDP_CONFIGURATION_SET },
> +	{ .offset = DP_SINK_COUNT, .end = DP_ADJUST_REQUEST_LANE2_3 },
> +	{ .offset = DP_SET_POWER },
> +	{ .offset = DP_EDP_DPCD_REV },
> +};
> +
> +static int i915_dpcd_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);
> +	uint8_t buf[16];
> +	ssize_t err;
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(i915_dpcd_debug); i++) {
> +		const struct dpcd_block *b = &i915_dpcd_debug[i];
> +		size_t size = b->end ? b->end - b->offset + 1 : (b->size ?: 1);
> +
> +		if (b->edp &&
> +		    connector->connector_type != DRM_MODE_CONNECTOR_eDP)
> +			continue;
> +
> +		/* low tech for now */
> +		if (WARN_ON(size > sizeof(buf)))
> +			continue;
> +
> +		err = drm_dp_dpcd_read(&intel_dp->aux, b->offset, buf, size);
> +		if (err <= 0) {
> +			DRM_ERROR("dpcd read (%zu bytes at %u) failed (%zd)\n",
> +				  size, b->offset, err);
> +			continue;
> +		}
> +
> +		seq_printf(m, "%04x: %*ph\n", b->offset, (int) size, buf);
> +	};
> +
> +	return 0;
> +}
> +
> +static int i915_dpcd_open(struct inode *inode, struct file *file)
> +{
> +	return single_open(file, i915_dpcd_show, inode->i_private);
> +}
> +
> +static const struct file_operations i915_dpcd_fops = {
> +	.owner = THIS_MODULE,
> +	.open = i915_dpcd_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
> + *
> + * Cleanup will be done by drm_connector_unregister() through a call to
> + * drm_debugfs_connector_remove().
> + *
> + * Returns 0 on success, negative error codes on error.
> + */
> +int i915_debugfs_connector_add(struct drm_connector *connector)
> +{
> +	struct dentry *root = connector->debugfs_entry;
> +
> +	/* The connector must have been registered beforehands. */
> +	if (!root)
> +		return -ENODEV;
> +
> +	if (connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort ||
> +	    connector->connector_type == DRM_MODE_CONNECTOR_eDP)
> +		debugfs_create_file("i915_dpcd", S_IRUGO, root, connector,
> +				    &i915_dpcd_fops);
> +
> +	return 0;
> +}
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index d42040fbd3c4..f8d42c7afda4 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -3095,6 +3095,7 @@ int i915_verify_lists(struct drm_device *dev);
>   /* i915_debugfs.c */
>   int i915_debugfs_init(struct drm_minor *minor);
>   void i915_debugfs_cleanup(struct drm_minor *minor);
> +int i915_debugfs_connector_add(struct drm_connector *connector);
>   #ifdef CONFIG_DEBUG_FS
>   void intel_display_crc_init(struct drm_device *dev);
>   #else
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 8d674f400d9a..69af47ebf77b 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -5348,6 +5348,8 @@ intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
>   		I915_WRITE(PEG_BAND_GAP_DATA, (temp & ~0xf) | 0xd);
>   	}
>   
> +	i915_debugfs_connector_add(connector);
> +
>   	return true;
>   }
>   

Looks good. I'm going to apply this patch and check it out.

Reviewed-by: Todd Previte <tprevite@gmail.com>
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