[Intel-gfx] [PATCH v2 22/27] drm/i915/lnl: Add CDCLK table

[Matt Roper]

On Thu, Sep 07, 2023 at 08:37:52AM -0700, Lucas De Marchi wrote:
> From: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>
> 
> Add a new Lunar Lake CDCLK table from BSpec and also a helper function
> in order to be able to find lowest possible CDCLK.
> 
> v2:
>   - Remove mdclk from the table as it's not needed (Matt Roper)
>   - Update waveform values to the latest from spec (Matt Roper)
>   - Rename functions and calculation to match by pixel rate (Lucas)
> 
> Bspec: 68861
> Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>
> Signed-off-by: Lucas De Marchi <lucas.demarchi at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_cdclk.c | 55 +++++++++++++++++++++-
>  1 file changed, 53 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c b/drivers/gpu/drm/i915/display/intel_cdclk.c
> index cfd01050f7f1..7307af2a4af5 100644
> --- a/drivers/gpu/drm/i915/display/intel_cdclk.c
> +++ b/drivers/gpu/drm/i915/display/intel_cdclk.c
> @@ -1382,6 +1382,31 @@ static const struct intel_cdclk_vals mtl_cdclk_table[] = {
>  	{}
>  };
>  
> +static const struct intel_cdclk_vals lnl_cdclk_table[] = {
> +	{ .refclk = 38400, .cdclk = 153600, .divider = 2, .ratio = 16, .waveform = 0xaaaa },
> +	{ .refclk = 38400, .cdclk = 172800, .divider = 2, .ratio = 16, .waveform = 0xad5a },
> +	{ .refclk = 38400, .cdclk = 192000, .divider = 2, .ratio = 16, .waveform = 0xb6b6 },
> +	{ .refclk = 38400, .cdclk = 211200, .divider = 2, .ratio = 16, .waveform = 0xdbb6 },
> +	{ .refclk = 38400, .cdclk = 230400, .divider = 2, .ratio = 16, .waveform = 0xeeee },
> +	{ .refclk = 38400, .cdclk = 249600, .divider = 2, .ratio = 16, .waveform = 0xf7de },
> +	{ .refclk = 38400, .cdclk = 268800, .divider = 2, .ratio = 16, .waveform = 0xfefe },
> +	{ .refclk = 38400, .cdclk = 288000, .divider = 2, .ratio = 16, .waveform = 0xfffe },
> +	{ .refclk = 38400, .cdclk = 307200, .divider = 2, .ratio = 16, .waveform = 0xffff },
> +	{ .refclk = 38400, .cdclk = 330000, .divider = 2, .ratio = 25, .waveform = 0xdbb6 },
> +	{ .refclk = 38400, .cdclk = 360000, .divider = 2, .ratio = 25, .waveform = 0xeeee },
> +	{ .refclk = 38400, .cdclk = 390000, .divider = 2, .ratio = 25, .waveform = 0xf7de },
> +	{ .refclk = 38400, .cdclk = 420000, .divider = 2, .ratio = 25, .waveform = 0xfefe },
> +	{ .refclk = 38400, .cdclk = 450000, .divider = 2, .ratio = 25, .waveform = 0xfffe },
> +	{ .refclk = 38400, .cdclk = 480000, .divider = 2, .ratio = 25, .waveform = 0xffff },
> +	{ .refclk = 38400, .cdclk = 487200, .divider = 2, .ratio = 29, .waveform = 0xfefe },
> +	{ .refclk = 38400, .cdclk = 522000, .divider = 2, .ratio = 29, .waveform = 0xfffe },
> +	{ .refclk = 38400, .cdclk = 556800, .divider = 2, .ratio = 29, .waveform = 0xffff },
> +	{ .refclk = 38400, .cdclk = 571200, .divider = 2, .ratio = 34, .waveform = 0xfefe },
> +	{ .refclk = 38400, .cdclk = 612000, .divider = 2, .ratio = 34, .waveform = 0xfffe },
> +	{ .refclk = 38400, .cdclk = 652800, .divider = 2, .ratio = 34, .waveform = 0xffff },
> +	{}
> +};
> +
>  static int bxt_calc_cdclk(struct drm_i915_private *dev_priv, int min_cdclk)
>  {
>  	const struct intel_cdclk_vals *table = dev_priv->display.cdclk.table;
> @@ -2504,12 +2529,35 @@ intel_set_cdclk_post_plane_update(struct intel_atomic_state *state)
>  	}
>  }
>  
> +static int
> +xe2lpd_cdclk_match_by_pixel_rate(struct drm_i915_private *i915, int pixel_rate)
> +{
> +	const struct intel_cdclk_vals *table = i915->display.cdclk.table;
> +	int i;
> +
> +	for (i = 0; table[i].refclk; i++) {
> +		if (table[i].refclk != i915->display.cdclk.hw.ref)
> +			continue;
> +
> +		if (table[i].refclk * table[i].ratio >= pixel_rate)
> +			return table[i].cdclk;
> +	}
> +
> +	drm_WARN(&i915->drm, 1,
> +		 "Cannot satisfy pixel rate %d with refclk %u\n",
> +		 pixel_rate, i915->display.cdclk.hw.ref);
> +
> +	return 0;
> +}
> +
>  static int intel_pixel_rate_to_cdclk(const struct intel_crtc_state *crtc_state)
>  {
>  	struct drm_i915_private *dev_priv = to_i915(crtc_state->uapi.crtc->dev);
>  	int pixel_rate = crtc_state->pixel_rate;
>  
> -	if (DISPLAY_VER(dev_priv) >= 10)
> +	if (DISPLAY_VER(dev_priv) >= 20)
> +		return xe2lpd_cdclk_match_by_pixel_rate(dev_priv, pixel_rate);

Is this actually what we want to be doing?  Generally this function
returns a minimum possible value cdclk value that could support the
pixel rate (e.g., pixel_rate / 2 on modern platforms), without caring
(yet) about the set of cdclk values that the platform is capable of
generating.  We then do some additional CRTC-level or device-level
adjustments to that minimum in intel_crtc_compute_min_cdclk and
intel_compute_min_cdclk, and only at the very end of the process (in
bxt_calc_cdclk) do we go into the table to find the lowest possible
clock greater than or equal to the adjusted minimum we had calculated.

>From what I can see, the minimum cdclk (as far as this specific function
is concerned) should still be half the pixel rate on Xe2 (bspec 68858:
"Pipe maximum pixel rate = 2 * CDCLK frequency * Pipe Ratio").  The only
thing that really changes with all the mdclk stuff is that cdclk and
mdclk are no longer fundamentally locked together in hardware; that's
why the table of possible cdclk settings in the bspec now has additional
rows where the cdclk value ranges anywhere from mdclk/4 to mdclk/2
(whereas on previous platforms every single row corresponded to an
mdclk/2 value).

tl;dr:  I don't think we want/need this hunk of the patch.


Matt

> +	else if (DISPLAY_VER(dev_priv) >= 10)
>  		return DIV_ROUND_UP(pixel_rate, 2);
>  	else if (DISPLAY_VER(dev_priv) == 9 ||
>  		 IS_BROADWELL(dev_priv) || IS_HASWELL(dev_priv))
> @@ -3591,7 +3639,10 @@ static const struct intel_cdclk_funcs i830_cdclk_funcs = {
>   */
>  void intel_init_cdclk_hooks(struct drm_i915_private *dev_priv)
>  {
> -	if (DISPLAY_VER(dev_priv) >= 14) {
> +	if (DISPLAY_VER(dev_priv) >= 20) {
> +		dev_priv->display.funcs.cdclk = &mtl_cdclk_funcs;
> +		dev_priv->display.cdclk.table = lnl_cdclk_table;
> +	} else if (DISPLAY_VER(dev_priv) >= 14) {
>  		dev_priv->display.funcs.cdclk = &mtl_cdclk_funcs;
>  		dev_priv->display.cdclk.table = mtl_cdclk_table;
>  	} else if (IS_DG2(dev_priv)) {
> -- 
> 2.40.1
> 

-- 
Matt Roper
Graphics Software Engineer
Linux GPU Platform Enablement
Intel Corporation