[Intel-gfx] [PATCH 05/10] drm/i915: Disable CLKOUT_DP bending on LPT/WPT as needed

[Paulo Zanoni]

2015-12-01 11:08 GMT-02:00  <ville.syrjala at linux.intel.com>:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
>
> When we want to use SPLL for FDI we want SSC, which means we have to
> disable clock bending for the PCH SSC reference (bend and spread are
> mtutually exclusive). So let's turn off bending when we want spread.
> In case the BIOS enabled clock bending for some reason we'll just turn
> it off and enable the spread mode instead.
>
> Not sure what happens if the BIOS is actually using the bend source for
> HDMI at this time, but I suppose it should be no worse than what already
> happens when we simply turn on the spread.
>
> We don't currently use the bend source for anything, and only use the
> PCH SSC reference for the SPLL to drive FDI (always with spread).
>
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/i915_reg.h      |  2 ++
>  drivers/gpu/drm/i915/intel_display.c | 65 ++++++++++++++++++++++++++++++++++--
>  2 files changed, 65 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 6d7ac192982d..fcc819f400a6 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -7320,6 +7320,7 @@ enum skl_disp_power_wells {
>  #define  SBI_READY                     (0x0<<0)
>
>  /* SBI offsets */
> +#define  SBI_SSCDIVINTPHASE                    0x0200
>  #define  SBI_SSCDIVINTPHASE6                   0x0600
>  #define   SBI_SSCDIVINTPHASE_DIVSEL_MASK       ((0x7f)<<1)
>  #define   SBI_SSCDIVINTPHASE_DIVSEL(x)         ((x)<<1)
> @@ -7327,6 +7328,7 @@ enum skl_disp_power_wells {
>  #define   SBI_SSCDIVINTPHASE_INCVAL(x)         ((x)<<8)
>  #define   SBI_SSCDIVINTPHASE_DIR(x)            ((x)<<15)
>  #define   SBI_SSCDIVINTPHASE_PROPAGATE         (1<<0)
> +#define  SBI_SSCDITHPHASE                      0x0204
>  #define  SBI_SSCCTL                            0x020c
>  #define  SBI_SSCCTL6                           0x060C
>  #define   SBI_SSCCTL_PATHALT                   (1<<3)
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index d049b087e8e6..c429029e3bed 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -8551,6 +8551,65 @@ static void lpt_disable_clkout_dp(struct drm_device *dev)
>         mutex_unlock(&dev_priv->sb_lock);
>  }
>
> +#define BEND_IDX(steps) ((50 + (steps)) / 5)
> +
> +static const uint16_t sscdivintphase[] = {
> +       [BEND_IDX( 50)] = 0x3B23,
> +       [BEND_IDX( 45)] = 0x3B23,
> +       [BEND_IDX( 40)] = 0x3C23,
> +       [BEND_IDX( 35)] = 0x3C23,
> +       [BEND_IDX( 30)] = 0x3D23,
> +       [BEND_IDX( 25)] = 0x3D23,
> +       [BEND_IDX( 20)] = 0x3E23,
> +       [BEND_IDX( 15)] = 0x3E23,
> +       [BEND_IDX( 10)] = 0x3F23,
> +       [BEND_IDX(  5)] = 0x3F23,
> +       [BEND_IDX(  0)] = 0x0025,
> +       [BEND_IDX( -5)] = 0x0025,
> +       [BEND_IDX(-10)] = 0x0125,
> +       [BEND_IDX(-15)] = 0x0125,
> +       [BEND_IDX(-20)] = 0x0225,
> +       [BEND_IDX(-25)] = 0x0225,
> +       [BEND_IDX(-30)] = 0x0325,
> +       [BEND_IDX(-35)] = 0x0325,
> +       [BEND_IDX(-40)] = 0x0425,
> +       [BEND_IDX(-45)] = 0x0425,
> +       [BEND_IDX(-50)] = 0x0525,
> +};
> +
> +/*
> + * Bend CLKOUT_DP
> + * steps -50 to 50 inclusive, in steps of 5
> + * < 0 slow down the clock, > 0 speed up the clock, 0 == no bend (135MHz)
> + * change in clock period = -(steps / 10) * 5.787 ps
> + */
> +static void lpt_bend_clkout_dp(struct drm_i915_private *dev_priv, int steps)

As far as I understood from your comments and the table, "int steps"
should always be a multiple of 5, right?

> +{
> +       uint32_t tmp;
> +
> +       int idx = BEND_IDX(steps);

So shouldn't we do the following?

if (WARN_ON(steps % 5 != 0))
        return;

> +
> +       if (WARN_ON(idx >= ARRAY_SIZE(sscdivintphase)))
> +               return;
> +
> +       mutex_lock(&dev_priv->sb_lock);
> +
> +       if (steps % 5 != 0)

Shouldn't this be "steps % 10 != 0"? Otherwise, we'll always assign 0x0.

Everything else looks correct.


> +               tmp = 0xAAAAAAAB;
> +       else
> +               tmp = 0x00000000;
> +       intel_sbi_write(dev_priv, SBI_SSCDITHPHASE, tmp, SBI_ICLK);
> +
> +       tmp = intel_sbi_read(dev_priv, SBI_SSCDIVINTPHASE, SBI_ICLK);
> +       tmp &= 0xffff0000;
> +       tmp |= sscdivintphase[idx];
> +       intel_sbi_write(dev_priv, SBI_SSCDIVINTPHASE, tmp, SBI_ICLK);
> +
> +       mutex_unlock(&dev_priv->sb_lock);
> +}
> +
> +#undef BEND_IDX
> +
>  static void lpt_init_pch_refclk(struct drm_device *dev)
>  {
>         struct intel_encoder *encoder;
> @@ -8566,10 +8625,12 @@ static void lpt_init_pch_refclk(struct drm_device *dev)
>                 }
>         }
>
> -       if (has_vga)
> +       if (has_vga) {
> +               lpt_bend_clkout_dp(to_i915(dev), 0);
>                 lpt_enable_clkout_dp(dev, true, true);
> -       else
> +       } else {
>                 lpt_disable_clkout_dp(dev);
> +       }
>  }
>
>  /*
> --
> 2.4.10
>
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-- 
Paulo Zanoni