Re: [PATCH 01/14] drm/i915/display: Modify debugfs for joiner to force n pipes

["Nautiyal, Ankit K" <ankit.k.nautiyal@intel.com>]

Hi Ville,

Thanks for the comments and suggestions. Will remove the extra things 
that are not required.

Please my response inline:

On 9/6/2024 8:16 PM, Ville Syrjälä wrote:
> On Fri, Sep 06, 2024 at 06:27:54PM +0530, Ankit Nautiyal wrote:
>> At the moment, the debugfs for joiner allows only to force enable/disable
>> pipe joiner for 2 pipes. Modify it to force join 'n' number of pipes,
>> where n is a valid pipe joiner configuration.
>> This will help in case of ultra joiner where 4 pipes are joined.
>>
>> v2:
>> -Fix commit message to state that only valid joiner config can be
>> forced. (Suraj)
>> -Rename the identifiers to have INTEL_BIG/NONE_JOINER_PIPES. (Suraj)
>>
>> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
>> ---
>>   .../drm/i915/display/intel_display_debugfs.c  | 71 ++++++++++++++++++-
>>   .../drm/i915/display/intel_display_types.h    |  8 ++-
>>   drivers/gpu/drm/i915/display/intel_dp.c       |  2 +-
>>   3 files changed, 77 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_display_debugfs.c b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
>> index 830b9eb60976..0ef573afd8a1 100644
>> --- a/drivers/gpu/drm/i915/display/intel_display_debugfs.c
>> +++ b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
>> @@ -1504,6 +1504,73 @@ static int intel_crtc_pipe_show(struct seq_file *m, void *unused)
>>   }
>>   DEFINE_SHOW_ATTRIBUTE(intel_crtc_pipe);
>>   
>> +static int i915_joiner_show(struct seq_file *m, void *data)
>> +{
>> +	struct intel_connector *connector = m->private;
>> +	struct drm_i915_private *i915 = to_i915(connector->base.dev);
>> +	int ret;
>> +
>> +	ret = drm_modeset_lock_single_interruptible(&i915->drm.mode_config.connection_mutex);
>> +	if (ret)
>> +		return ret;
> What does that lock do for us?
This might be leftover from other debugfs, I'll remove this.
>
>> +
>> +	seq_printf(m, "Force_joined_pipes: %d\n", connector->force_joined_pipes);
> This should just be thae bare number. Adding other junk in there just
> complicates matters if anyone has to parse this.

Alright, will just have the number (force joined pipes).

>
>> +
>> +	drm_modeset_unlock(&i915->drm.mode_config.connection_mutex);
>> +
>> +	return ret;
>> +}
>> +
>> +static ssize_t i915_joiner_write(struct file *file,
>> +				 const char __user *ubuf,
>> +				 size_t len, loff_t *offp)
>> +{
>> +	struct seq_file *m = file->private_data;
>> +	struct intel_connector *connector = m->private;
>> +	struct drm_i915_private *i915 = to_i915(connector->base.dev);
>> +	int force_join_pipes = 0;
>> +	int ret;
>> +
>> +	if (len == 0)
>> +		return 0;
>> +
>> +	drm_dbg(&i915->drm,
>> +		"Copied %zu bytes from user to force joiner\n", len);
> Leftover debug junk.

Will remove this.


>
>> +
>> +	ret = kstrtoint_from_user(ubuf, len, 0, &force_join_pipes);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	drm_dbg(&i915->drm, "Got %d for force joining pipes\n", force_join_pipes);
> More.

Will get rid of this.


>
>> +
>> +	if (force_join_pipes < INTEL_NONE_JOINER_PIPES ||
>> +	    force_join_pipes >= INTEL_INVALID_JOINER_PIPES) {
>> +		drm_dbg(&i915->drm, "Ignoring Invalid num of pipes %d for force joining\n",
>> +			force_join_pipes);
>> +		connector->force_joined_pipes = INTEL_NONE_JOINER_PIPES;
>> +	} else {
>> +		connector->force_joined_pipes = force_join_pipes;
>> +	}
> I think just something like
> switch (num_pipes) {
> case 0: /* or should 1 be the default? */
> case 2:
> case 4:
> 	break;
> default:
> 	bad;
> }
>
> should do for validation.
>
>> +
>> +	*offp += len;
> I don't suppose there's any kind of helper for creating a debugfs
> file with a standard type, with some kind of caller specified
> validation function? Would avoid having to hand roll all this
> read syscall cruft for what is a fairly common usecase...
>
>> +
>> +	return len;
>> +}
>> +
>> +static int i915_joiner_open(struct inode *inode, struct file *file)
>> +{
>> +	return single_open(file, i915_joiner_show, inode->i_private);
>> +}
>> +
>> +static const struct file_operations i915_joiner_fops = {
>> +	.owner = THIS_MODULE,
>> +	.open = i915_joiner_open,
>> +	.read = seq_read,
>> +	.llseek = seq_lseek,
>> +	.release = single_release,
>> +	.write = i915_joiner_write
>> +};
>> +
>>   /**
>>    * intel_connector_debugfs_add - add i915 specific connector debugfs files
>>    * @connector: pointer to a registered intel_connector
>> @@ -1553,8 +1620,8 @@ void intel_connector_debugfs_add(struct intel_connector *connector)
>>   	if (DISPLAY_VER(i915) >= 11 &&
>>   	    (connector_type == DRM_MODE_CONNECTOR_DisplayPort ||
>>   	     connector_type == DRM_MODE_CONNECTOR_eDP)) {
>> -		debugfs_create_bool("i915_bigjoiner_force_enable", 0644, root,
>> -				    &connector->force_bigjoiner_enable);
>> +		debugfs_create_file("i915_joiner_force_enable", 0644, root,
>> +				    connector, &i915_joiner_fops);
>>   	}
>>   
>>   	if (connector_type == DRM_MODE_CONNECTOR_DSI ||
>> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
>> index 733de5edcfdb..c213fb61ceb7 100644
>> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
>> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
>> @@ -486,6 +486,12 @@ struct intel_hdcp {
>>   	enum transcoder stream_transcoder;
>>   };
>>   
>> +enum intel_joiner_pipe_count {
>> +	INTEL_NONE_JOINER_PIPES = 0,
>> +	INTEL_BIG_JOINER_PIPES = 2,
>> +	INTEL_INVALID_JOINER_PIPES,
>> +};
> That just looks like obfuscation to me.
> Just a bare number should do.

I was thinking to use these in rest of the places to avoid magic 
numbers, but if it makes it unreadable, I can do away with this.


Thanks & regards,

Ankit


>
>> +
>>   struct intel_connector {
>>   	struct drm_connector base;
>>   	/*
>> @@ -524,7 +530,7 @@ struct intel_connector {
>>   
>>   	struct intel_dp *mst_port;
>>   
>> -	bool force_bigjoiner_enable;
>> +	enum intel_joiner_pipe_count force_joined_pipes;
>>   
>>   	struct {
>>   		struct drm_dp_aux *dsc_decompression_aux;
>> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
>> index a1fcedfd404b..862a460c32b7 100644
>> --- a/drivers/gpu/drm/i915/display/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
>> @@ -1271,7 +1271,7 @@ bool intel_dp_need_joiner(struct intel_dp *intel_dp,
>>   		return false;
>>   
>>   	return clock > i915->display.cdclk.max_dotclk_freq || hdisplay > 5120 ||
>> -	       connector->force_bigjoiner_enable;
>> +	       connector->force_joined_pipes == INTEL_BIG_JOINER_PIPES;
>>   }
>>   
>>   bool intel_dp_has_dsc(const struct intel_connector *connector)
>> -- 
>> 2.45.2