On Wed, Feb 21, 2024 at 09:53:21AM +0200, Jouni Högander wrote:
> Current fast and IO wake lines calculation is assuming fast wake sync
> length is 18 pulses. Let's improve this by checking the actual length.
>
> Also 10 us IO buffer wake time is currently assumed. This is not the case
> with LunarLake and beyond. Fix this by adding getter for IO wake time and
> return values there according to Bspec.
>
> Bspec: 65450
>
> Signed-off-by: Jouni Högander <jouni.hogander@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/display/intel_psr.c | 40 +++++++++++++++++++-----
> 1 file changed, 33 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c
> index 72cadad09db5..4a1e07411716 100644
> --- a/drivers/gpu/drm/i915/display/intel_psr.c
> +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> @@ -1150,6 +1150,28 @@ static bool _lnl_compute_alpm_params(struct intel_dp *intel_dp,
> return true;
> }
>
> +/*
> + * From Bspec:
> + *
> + * For Xe2 and beyond
> + * RBR 15us, HBR1 11us, higher rates 10us
> + *
> + * For pre-Xe2
> + * 10 us
> + */
> +static int get_io_wake_time(struct intel_dp *intel_dp,
No point in passing that. You can dig out the i915 from the crtc state.
> + struct intel_crtc_state *crtc_state)
const
> +{
> + struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> +
> + if (DISPLAY_VER(i915) < 20 || crtc_state->port_clock > 270000)
> + return 10;
> + else if (crtc_state->port_clock > 162000)
> + return 11;
> + else
> + return 15;
The new rate dependent stuff should be a separate patch.
And looks like the 10 usec will give us 44 usec io wake time, so
that should probably be a separate patch as well, to avoid
any functional changes when we introduce the formula.
> +}
> +
> static bool _compute_alpm_params(struct intel_dp *intel_dp,
> struct intel_crtc_state *crtc_state)
> {
> @@ -1157,13 +1179,17 @@ static bool _compute_alpm_params(struct intel_dp *intel_dp,
> int io_wake_lines, io_wake_time, fast_wake_lines, fast_wake_time;
> u8 max_wake_lines;
>
> - if (DISPLAY_VER(i915) >= 12) {
> - io_wake_time = 42;
> - /*
> - * According to Bspec it's 42us, but based on testing
> - * it is not enough -> use 45 us.
> - */
> - fast_wake_time = 45;
> + if (intel_dp->get_aux_fw_sync_len) {
> + int io_wake_time = get_io_wake_time(intel_dp, crtc_state);
Looks like this will shadow the variable you're trying to change.
Does the compiler not complain about this?
> + int tfw_exit_latency = 20; /* eDP spec */
> + int phy_wake = 4; /* eDP spec */
> + int preamble = 8; /* eDP spec */
> + int precharge = intel_dp->get_aux_fw_sync_len() - preamble;
> +
> + io_wake_time = max(precharge, io_wake_time) + preamble +
> + phy_wake + tfw_exit_latency;
> + fast_wake_time = precharge + preamble + phy_wake +
> + tfw_exit_latency;
>
> /* TODO: Check how we can use ALPM_CTL fast wake extended field */
> max_wake_lines = 12;
I would also convert the older platforms to use the formula.
We do need to reverse calculate the io buffer on latency since
AFAICS it's not directly specified in bspec. But I think
that's better than not converting it since with the formula we
can't totally screw things up when eg. changing the precharge
length.
--
Ville Syrjälä
Intel
