linux-kernel - Re: [PATCH] drm: atmel-hlcdc: use a default gamma ramp if none is specified

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Date:   Mon, 3 Jul 2017 13:53:28 +0200
From:   Peter Rosin <peda@...ntia.se>
To:     Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:     linux-kernel@...r.kernel.org, David Airlie <airlied@...ux.ie>,
        dri-devel@...ts.freedesktop.org,
        Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>
Subject: Re: [PATCH] drm: atmel-hlcdc: use a default gamma ramp if none is
 specified

On 2017-07-03 13:31, Boris Brezillon wrote:
> On Mon,  3 Jul 2017 11:42:10 +0200
> Peter Rosin <peda@...ntia.se> wrote:
> 
>> At init and if the gamma_lut property is ever removed, the clut
>> registers must be programmed with a default gamma ramp instead of
>> being left in some unknown state.
>>
>> Fixes: 364a7bf574eb ("drm: atmel-hlcdc: add support for 8-bit color lookup table mode")
>> Signed-off-by: Peter Rosin <peda@...ntia.se>
>> ---
>>  drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_plane.c | 17 ++++++++++++++++-
>>  1 file changed, 16 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_plane.c b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_plane.c
>> index b5bd9b0..0ccd93c 100644
>> --- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_plane.c
>> +++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_plane.c
>> @@ -429,6 +429,14 @@ static void atmel_hlcdc_plane_update_format(struct atmel_hlcdc_plane *plane,
>>  				    ATMEL_HLCDC_LAYER_FORMAT_CFG, cfg);
>>  }
>>  
>> +static void atmel_hlcdc_default_gamma_ramp(struct atmel_hlcdc_layer *layer)
>> +{
>> +	int idx;
>> +
>> +	for (idx = 0; idx < ATMEL_HLCDC_CLUT_SIZE; idx++)
>> +		atmel_hlcdc_layer_write_clut(layer, idx, idx * 0x10101);
>> +}
>> +
>>  static void atmel_hlcdc_plane_update_clut(struct atmel_hlcdc_plane *plane)
>>  {
>>  	struct drm_crtc *crtc = plane->base.crtc;
>> @@ -438,9 +446,14 @@ static void atmel_hlcdc_plane_update_clut(struct atmel_hlcdc_plane *plane)
>>  	if (!crtc || !crtc->state)
>>  		return;
>>  
>> -	if (!crtc->state->color_mgmt_changed || !crtc->state->gamma_lut)
>> +	if (!crtc->state->color_mgmt_changed)
>>  		return;
>>  
>> +	if (!crtc->state->gamma_lut) {
>> +		atmel_hlcdc_default_gamma_ramp(&plane->layer);
> 
> Hm, I'd prefer to have state->gamma_lut properly initialized in
> atmel_hlcdc_crtc_reset(), this way you don't have to do that in the
> update path.

The gamma_lut property can be removed, so you have to handle it here anyway. No?

Cheers,
peda

>> +		return;
>> +	}
>> +
>>  	lut = (struct drm_color_lut *)crtc->state->gamma_lut->data;
>>  
>>  	for (idx = 0; idx < ATMEL_HLCDC_CLUT_SIZE; idx++, lut++) {
>> @@ -918,6 +931,8 @@ static int atmel_hlcdc_plane_init_properties(struct atmel_hlcdc_plane *plane,
>>  					    0x40040890);
>>  	}
>>  
>> +	atmel_hlcdc_default_gamma_ramp(&plane->layer);
>> +
>>  	return 0;
>>  }
>>  
>