Re: [PATCH] drm/i915/dp: Fix the t11_t12 delay for non GEN 9 LP platforms at HW readout and HW write

Ville Syrjälä
2017-06-21T20:04:02Z

On Wed, Jun 21, 2017 at 12:37:43PM -0700, Manasi Navare wrote:
> According to the eDP spec the minimum value for panel power cycle delay
> (t11_t12) is 500ms and as per the Bspec, PP_DIVISOR panel power cycle
> delay field should be programmed to "+1" value. Eg: To have a delay
> of 500ms this should be programmed to 6. This patch fixes the write
> by adding +1 to the pp_div value so it programs the correct min
> required panel power cycle delay.
> Since we program it to +1 value, when we perform HW readout, this
> value should subtract 1 before verifying pps state. This patch makes
> this correction as well to avoid "PPS state mismatch" error.
> This patch also adds a case where if the readout is 0 for the first readout,
> then read it as 0, dont subtract.
>
> Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> Cc: Clint Taylor <Clinton.A.Taylor@intel.com>
> ---
> drivers/gpu/drm/i915/intel_dp.c | 22 +++++++++++-----------
> 1 file changed, 11 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index bca4ac1..089e373 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -5149,6 +5149,7 @@ intel_pps_readout_hw_state(struct drm_i915_private *dev_priv,
> struct intel_dp *intel_dp, struct edp_power_seq *seq)
> {
> u32 pp_on, pp_off, pp_div = 0, pp_ctl = 0;
> + u16 pp_cycle_delay = 0;
> struct pps_registers regs;
>
> intel_pps_get_registers(dev_priv, intel_dp, &regs);
> @@ -5177,17 +5178,16 @@ intel_pps_readout_hw_state(struct drm_i915_private *dev_priv,
> seq->t10 = (pp_off & PANEL_POWER_DOWN_DELAY_MASK) >>
> PANEL_POWER_DOWN_DELAY_SHIFT;
>
> - if (IS_GEN9_LP(dev_priv) || HAS_PCH_CNP(dev_priv)) {
> - u16 tmp = (pp_ctl & BXT_POWER_CYCLE_DELAY_MASK) >>
> + if (IS_GEN9_LP(dev_priv) || HAS_PCH_CNP(dev_priv))
> + pp_cycle_delay = (pp_ctl & BXT_POWER_CYCLE_DELAY_MASK) >>
> BXT_POWER_CYCLE_DELAY_SHIFT;
> - if (tmp > 0)
> - seq->t11_t12 = (tmp - 1) * 1000;
> - else
> - seq->t11_t12 = 0;
> - } else {
> - seq->t11_t12 = ((pp_div & PANEL_POWER_CYCLE_DELAY_MASK) >>
> - PANEL_POWER_CYCLE_DELAY_SHIFT) * 1000;
> - }
> + else
> + pp_cycle_delay = (pp_div & PANEL_POWER_CYCLE_DELAY_MASK) >>
> + PANEL_POWER_CYCLE_DELAY_SHIFT;
> + if (pp_cycle_delay > 0)
> + seq->t11_t12 = (pp_cycle_delay - 1) * 1000;
> + else
> + seq->t11_t12 = 0;

I think it's probably easier to go the other way and just add the +100
msec to the vbt delay, and nuke the BXT/CNP special casing in the code.

> }
>
> static void
> @@ -5341,7 +5341,7 @@ intel_dp_init_panel_power_sequencer_registers(struct drm_device *dev,
> << BXT_POWER_CYCLE_DELAY_SHIFT);
> } else {
> pp_div = ((100 * div)/2 - 1) << PP_REFERENCE_DIVIDER_SHIFT;
> - pp_div |= (DIV_ROUND_UP(seq->t11_t12, 1000)
> + pp_div |= (DIV_ROUND_UP(seq->t11_t12 + 1, 1000)
> << PANEL_POWER_CYCLE_DELAY_SHIFT);
> }
>
> --
> 2.1.4

--
Ville Syrjälä
Intel OTC