Re: [PATCH] drm/msm/mdp5: high precision vblank timestamp support

[Archit Taneja <architt@codeaurora.org>]

On 10/27/2015 05:33 AM, Rob Clark wrote:
> On Mon, Oct 26, 2015 at 5:54 AM, Archit Taneja <architt@codeaurora.org> wrote:
>> MDP5 has line count and frame count registers for each interface. Enable
>> these counters and use them to implement the get_vblank_timestamp drm
>> driver op.
>>
>> The line counter starts with the value 1 at the beginning of the VSYNC
>> pulse and ends with value VTOTAL at the end of VFP. This value is used
>> to determine whether we're in blanking period or not, and an adjusted
>> value of this counter is used to get vpos as expected by
>> get_scanout_position. Since there is no way to calculate hpos, we always
>> set it to 0.
>
> What are the odds that mdp(n!=5) could support the same?  If/when that
> ever happens I could see making some of this helpers to duplicate a
> bit less in mdpN backend.. but I guess also fine to cross that bridge
> when we come to it.  Other than that, lgtm, thanks

The MDP4 line counter only loops within the active region, making it 
sort of ineffective. That's the main reason why I didn't attempt to 
implement it for mdp4.

There seems to be a 12 bit frame counter available to implement a
vblank counter, but without the line counter, I'm not sure if that'll
be any better than using the software vblank counter.

Archit

>
> BR,
> -R
>
>> Signed-off-by: Archit Taneja <architt@codeaurora.org>
>> ---
>>   drivers/gpu/drm/msm/mdp/mdp5/mdp5_encoder.c |  18 ++++
>>   drivers/gpu/drm/msm/mdp/mdp5/mdp5_kms.c     | 129 ++++++++++++++++++++++++++++
>>   drivers/gpu/drm/msm/mdp/mdp5/mdp5_kms.h     |   2 +
>>   3 files changed, 149 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/msm/mdp/mdp5/mdp5_encoder.c b/drivers/gpu/drm/msm/mdp/mdp5/mdp5_encoder.c
>> index c9e32b0..a019656 100644
>> --- a/drivers/gpu/drm/msm/mdp/mdp5/mdp5_encoder.c
>> +++ b/drivers/gpu/drm/msm/mdp/mdp5/mdp5_encoder.c
>> @@ -293,6 +293,24 @@ static const struct drm_encoder_helper_funcs mdp5_encoder_helper_funcs = {
>>          .enable = mdp5_encoder_enable,
>>   };
>>
>> +int mdp5_encoder_get_linecount(struct drm_encoder *encoder)
>> +{
>> +       struct mdp5_encoder *mdp5_encoder = to_mdp5_encoder(encoder);
>> +       struct mdp5_kms *mdp5_kms = get_kms(encoder);
>> +       int intf = mdp5_encoder->intf.num;
>> +
>> +       return mdp5_read(mdp5_kms, REG_MDP5_INTF_LINE_COUNT(intf));
>> +}
>> +
>> +u32 mdp5_encoder_get_framecount(struct drm_encoder *encoder)
>> +{
>> +       struct mdp5_encoder *mdp5_encoder = to_mdp5_encoder(encoder);
>> +       struct mdp5_kms *mdp5_kms = get_kms(encoder);
>> +       int intf = mdp5_encoder->intf.num;
>> +
>> +       return mdp5_read(mdp5_kms, REG_MDP5_INTF_FRAME_COUNT(intf));
>> +}
>> +
>>   int mdp5_encoder_set_split_display(struct drm_encoder *encoder,
>>                                          struct drm_encoder *slave_encoder)
>>   {
>> diff --git a/drivers/gpu/drm/msm/mdp/mdp5/mdp5_kms.c b/drivers/gpu/drm/msm/mdp/mdp5/mdp5_kms.c
>> index b532faa..e115318 100644
>> --- a/drivers/gpu/drm/msm/mdp/mdp5/mdp5_kms.c
>> +++ b/drivers/gpu/drm/msm/mdp/mdp5/mdp5_kms.c
>> @@ -468,6 +468,127 @@ static int get_clk(struct platform_device *pdev, struct clk **clkp,
>>          return 0;
>>   }
>>
>> +static struct drm_encoder *get_encoder_from_crtc(struct drm_crtc *crtc)
>> +{
>> +       struct drm_device *dev = crtc->dev;
>> +       struct drm_encoder *encoder;
>> +
>> +       drm_for_each_encoder(encoder, dev)
>> +               if (encoder->crtc == crtc)
>> +                       return encoder;
>> +
>> +       return NULL;
>> +}
>> +
>> +static int mdp5_get_scanoutpos(struct drm_device *dev, unsigned int pipe,
>> +                              unsigned int flags, int *vpos, int *hpos,
>> +                              ktime_t *stime, ktime_t *etime,
>> +                              const struct drm_display_mode *mode)
>> +{
>> +       struct msm_drm_private *priv = dev->dev_private;
>> +       struct drm_crtc *crtc;
>> +       struct drm_encoder *encoder;
>> +       int line, vsw, vbp, vactive_start, vactive_end, vfp_end;
>> +       int ret = 0;
>> +
>> +       crtc = priv->crtcs[pipe];
>> +       if (!crtc) {
>> +               DRM_ERROR("Invalid crtc %d\n", pipe);
>> +               return 0;
>> +       }
>> +
>> +       encoder = get_encoder_from_crtc(crtc);
>> +       if (!encoder) {
>> +               DRM_ERROR("no encoder found for crtc %d\n", pipe);
>> +               return 0;
>> +       }
>> +
>> +       ret |= DRM_SCANOUTPOS_VALID | DRM_SCANOUTPOS_ACCURATE;
>> +
>> +       vsw = mode->crtc_vsync_end - mode->crtc_vsync_start;
>> +       vbp = mode->crtc_vtotal - mode->crtc_vsync_end;
>> +
>> +       /*
>> +        * the line counter is 1 at the start of the VSYNC pulse and VTOTAL at
>> +        * the end of VFP. Translate the porch values relative to the line
>> +        * counter positions.
>> +        */
>> +
>> +       vactive_start = vsw + vbp + 1;
>> +
>> +       vactive_end = vactive_start + mode->crtc_vdisplay;
>> +
>> +       /* last scan line before VSYNC */
>> +       vfp_end = mode->crtc_vtotal;
>> +
>> +       if (stime)
>> +               *stime = ktime_get();
>> +
>> +       line = mdp5_encoder_get_linecount(encoder);
>> +
>> +       if (line < vactive_start) {
>> +               line -= vactive_start;
>> +               ret |= DRM_SCANOUTPOS_IN_VBLANK;
>> +       } else if (line > vactive_end) {
>> +               line = line - vfp_end - vactive_start;
>> +               ret |= DRM_SCANOUTPOS_IN_VBLANK;
>> +       } else {
>> +               line -= vactive_start;
>> +       }
>> +
>> +       *vpos = line;
>> +       *hpos = 0;
>> +
>> +       if (etime)
>> +               *etime = ktime_get();
>> +
>> +       return ret;
>> +}
>> +
>> +static int mdp5_get_vblank_timestamp(struct drm_device *dev, unsigned int pipe,
>> +                                    int *max_error,
>> +                                    struct timeval *vblank_time,
>> +                                    unsigned flags)
>> +{
>> +       struct msm_drm_private *priv = dev->dev_private;
>> +       struct drm_crtc *crtc;
>> +
>> +       if (pipe < 0 || pipe >= priv->num_crtcs) {
>> +               DRM_ERROR("Invalid crtc %d\n", pipe);
>> +               return -EINVAL;
>> +       }
>> +
>> +       crtc = priv->crtcs[pipe];
>> +       if (!crtc) {
>> +               DRM_ERROR("Invalid crtc %d\n", pipe);
>> +               return -EINVAL;
>> +       }
>> +
>> +       return drm_calc_vbltimestamp_from_scanoutpos(dev, pipe, max_error,
>> +                                                    vblank_time, flags,
>> +                                                    &crtc->mode);
>> +}
>> +
>> +static u32 mdp5_get_vblank_counter(struct drm_device *dev, unsigned int pipe)
>> +{
>> +       struct msm_drm_private *priv = dev->dev_private;
>> +       struct drm_crtc *crtc;
>> +       struct drm_encoder *encoder;
>> +
>> +       if (pipe < 0 || pipe >= priv->num_crtcs)
>> +               return 0;
>> +
>> +       crtc = priv->crtcs[pipe];
>> +       if (!crtc)
>> +               return 0;
>> +
>> +       encoder = get_encoder_from_crtc(crtc);
>> +       if (!encoder)
>> +               return 0;
>> +
>> +       return mdp5_encoder_get_framecount(encoder);
>> +}
>> +
>>   struct msm_kms *mdp5_kms_init(struct drm_device *dev)
>>   {
>>          struct platform_device *pdev = dev->platformdev;
>> @@ -590,6 +711,8 @@ struct msm_kms *mdp5_kms_init(struct drm_device *dev)
>>                                  !config->hw->intf.base[i])
>>                          continue;
>>                  mdp5_write(mdp5_kms, REG_MDP5_INTF_TIMING_ENGINE_EN(i), 0);
>> +
>> +               mdp5_write(mdp5_kms, REG_MDP5_INTF_FRAME_LINE_COUNT_EN(i), 0x3);
>>          }
>>          mdp5_disable(mdp5_kms);
>>          mdelay(16);
>> @@ -635,6 +758,12 @@ struct msm_kms *mdp5_kms_init(struct drm_device *dev)
>>          dev->mode_config.max_width = config->hw->lm.max_width;
>>          dev->mode_config.max_height = config->hw->lm.max_height;
>>
>> +       dev->driver->get_vblank_timestamp = mdp5_get_vblank_timestamp;
>> +       dev->driver->get_scanout_position = mdp5_get_scanoutpos;
>> +       dev->driver->get_vblank_counter = mdp5_get_vblank_counter;
>> +       dev->max_vblank_count = 0xffffffff;
>> +       dev->vblank_disable_immediate = true;
>> +
>>          return kms;
>>
>>   fail:
>> diff --git a/drivers/gpu/drm/msm/mdp/mdp5/mdp5_kms.h b/drivers/gpu/drm/msm/mdp/mdp5/mdp5_kms.h
>> index 84f65d4..00730ba 100644
>> --- a/drivers/gpu/drm/msm/mdp/mdp5/mdp5_kms.h
>> +++ b/drivers/gpu/drm/msm/mdp/mdp5/mdp5_kms.h
>> @@ -222,6 +222,8 @@ struct drm_encoder *mdp5_encoder_init(struct drm_device *dev,
>>                  struct mdp5_interface *intf, struct mdp5_ctl *ctl);
>>   int mdp5_encoder_set_split_display(struct drm_encoder *encoder,
>>                                          struct drm_encoder *slave_encoder);
>> +int mdp5_encoder_get_linecount(struct drm_encoder *encoder);
>> +u32 mdp5_encoder_get_framecount(struct drm_encoder *encoder);
>>
>>   #ifdef CONFIG_DRM_MSM_DSI
>>   struct drm_encoder *mdp5_cmd_encoder_init(struct drm_device *dev,
>> --
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
>> hosted by The Linux Foundation
>>
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