drm/i915/skl: Deinit/init the display at suspend/resume

We need to re-init the display hardware when going out of suspend. This
includes:

  - Hooking the PCH to the reset logic
  - Restoring CDCDLK
  - Enabling the DDB power

Among those, only the CDCDLK one is a bit tricky. There's some
complexity in that:

  - DPLL0 (which is the source for CDCLK) has two VCOs, each with a set
    of supported frequencies. As eDP also uses DPLL0 for its link rate,
    once DPLL0 is on, we restrict the possible eDP link rates the chosen
    VCO.
  - CDCLK also limits the bandwidth available to push pixels.

So, as a first step, this commit restore what the BIOS set, until I can
do more testing.

In case that's of interest for the reviewer, I've unit tested the
function that derives the decimal frequency field:

  #include <stdio.h>
  #include <stdint.h>
  #include <assert.h>

  #define ARRAY_SIZE(x) (sizeof(x) / sizeof(*(x)))

  static const struct dpll_freq {
          unsigned int freq;
          unsigned int decimal;
  } freqs[] = {
          { .freq = 308570, .decimal = 0b01001100111},
          { .freq = 337500, .decimal = 0b01010100001},
          { .freq = 432000, .decimal = 0b01101011110},
          { .freq = 450000, .decimal = 0b01110000010},
          { .freq = 540000, .decimal = 0b10000110110},
          { .freq = 617140, .decimal = 0b10011010000},
          { .freq = 675000, .decimal = 0b10101000100},
  };

  static void intbits(unsigned int v)
  {
          int i;

          for(i = 10; i >= 0; i--)
                  putchar('0' + ((v >> i) & 1));
  }

  static unsigned int freq_decimal(unsigned int freq /* in kHz */)
  {
          return (freq - 1000) / 500;
  }

  static void test_freq(const struct dpll_freq *entry)
  {
          unsigned int decimal = freq_decimal(entry->freq);

          printf("freq: %d, expected: ", entry->freq);
          intbits(entry->decimal);
          printf(", got: ");
          intbits(decimal);
          putchar('\n');

          assert(decimal == entry->decimal);
  }

  int main(int argc, char **argv)
  {
          int i;

          for (i = 0; i < ARRAY_SIZE(freqs); i++)
                  test_freq(&freqs[i]);

          return 0;
  }

v2:
  - Rebase on top of -nightly
  - Use (freq - 1000) / 500 for the decimal frequency (Ville)
  - Fix setting the enable bit of HSW_NDE_RSTWRN_OPT (Ville)
  - Rename skl_display_{resume,suspend} to skl_{init,uninit}_cdclk to
    be consistent with the BXT code (Ville)
  - Store boot CDCLK in ddi_pll_init (Ville)
  - Merge dev_priv's skl_boot_cdclk into cdclk_freq
  - Use LCPLL_PLL_LOCK instead of (1 << 30) (Ville)
  - Replace various '0' by SKL_DPLL0 to be a bit more explicit that
    we're programming DPLL0
  - Busy poll the PCU before doing the frequency change. It takes about
    3/4 cycles, each separated by 10us, to get the ACK from the CPU
    (Ville)

v3:
  - Restore dev_priv->skl_boot_cdclk, leaving unification with
    dev_priv->cdclk_freq for a later patch (Daniel, Ville)

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 208 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 048565572764..268043f65dd8 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -5527,6 +5527,214 @@ void broxton_uninit_cdclk(struct drm_device *dev)
 	intel_display_power_put(dev_priv, POWER_DOMAIN_PLLS);
 }
 
+static const struct skl_cdclk_entry {
+	unsigned int freq;
+	unsigned int vco;
+} skl_cdclk_frequencies[] = {
+	{ .freq = 308570, .vco = 8640 },
+	{ .freq = 337500, .vco = 8100 },
+	{ .freq = 432000, .vco = 8640 },
+	{ .freq = 450000, .vco = 8100 },
+	{ .freq = 540000, .vco = 8100 },
+	{ .freq = 617140, .vco = 8640 },
+	{ .freq = 675000, .vco = 8100 },
+};
+
+static unsigned int skl_cdclk_decimal(unsigned int freq)
+{
+	return (freq - 1000) / 500;
+}
+
+static unsigned int skl_cdclk_get_vco(unsigned int freq)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(skl_cdclk_frequencies); i++) {
+		const struct skl_cdclk_entry *e = &skl_cdclk_frequencies[i];
+
+		if (e->freq == freq)
+			return e->vco;
+	}
+
+	return 8100;
+}
+
+static void
+skl_dpll0_enable(struct drm_i915_private *dev_priv, unsigned int required_vco)
+{
+	unsigned int min_freq;
+	u32 val;
+
+	/* select the minimum CDCLK before enabling DPLL 0 */
+	val = I915_READ(CDCLK_CTL);
+	val &= ~CDCLK_FREQ_SEL_MASK | ~CDCLK_FREQ_DECIMAL_MASK;
+	val |= CDCLK_FREQ_337_308;
+
+	if (required_vco == 8640)
+		min_freq = 308570;
+	else
+		min_freq = 337500;
+
+	val = CDCLK_FREQ_337_308 | skl_cdclk_decimal(min_freq);
+
+	I915_WRITE(CDCLK_CTL, val);
+	POSTING_READ(CDCLK_CTL);
+
+	/*
+	 * We always enable DPLL0 with the lowest link rate possible, but still
+	 * taking into account the VCO required to operate the eDP panel at the
+	 * desired frequency. The usual DP link rates operate with a VCO of
+	 * 8100 while the eDP 1.4 alternate link rates need a VCO of 8640.
+	 * The modeset code is responsible for the selection of the exact link
+	 * rate later on, with the constraint of choosing a frequency that
+	 * works with required_vco.
+	 */
+	val = I915_READ(DPLL_CTRL1);
+
+	val &= ~(DPLL_CTRL1_HDMI_MODE(SKL_DPLL0) | DPLL_CTRL1_SSC(SKL_DPLL0) |
+		 DPLL_CTRL1_LINK_RATE_MASK(SKL_DPLL0));
+	val |= DPLL_CTRL1_OVERRIDE(SKL_DPLL0);
+	if (required_vco == 8640)
+		val |= DPLL_CTRL1_LINK_RATE(DPLL_CTRL1_LINK_RATE_1080,
+					    SKL_DPLL0);
+	else
+		val |= DPLL_CTRL1_LINK_RATE(DPLL_CTRL1_LINK_RATE_810,
+					    SKL_DPLL0);
+
+	I915_WRITE(DPLL_CTRL1, val);
+	POSTING_READ(DPLL_CTRL1);
+
+	I915_WRITE(LCPLL1_CTL, I915_READ(LCPLL1_CTL) | LCPLL_PLL_ENABLE);
+
+	if (wait_for(I915_READ(LCPLL1_CTL) & LCPLL_PLL_LOCK, 5))
+		DRM_ERROR("DPLL0 not locked\n");
+}
+
+static bool skl_cdclk_pcu_ready(struct drm_i915_private *dev_priv)
+{
+	int ret;
+	u32 val;
+
+	/* inform PCU we want to change CDCLK */
+	val = SKL_CDCLK_PREPARE_FOR_CHANGE;
+	mutex_lock(&dev_priv->rps.hw_lock);
+	ret = sandybridge_pcode_read(dev_priv, SKL_PCODE_CDCLK_CONTROL, &val);
+	mutex_unlock(&dev_priv->rps.hw_lock);
+
+	return ret == 0 && (val & SKL_CDCLK_READY_FOR_CHANGE);
+}
+
+static bool skl_cdclk_wait_for_pcu_ready(struct drm_i915_private *dev_priv)
+{
+	unsigned int i;
+
+	for (i = 0; i < 15; i++) {
+		if (skl_cdclk_pcu_ready(dev_priv))
+			return true;
+		udelay(10);
+	}
+
+	return false;
+}
+
+static void skl_set_cdclk(struct drm_i915_private *dev_priv, unsigned int freq)
+{
+	u32 freq_select, pcu_ack;
+
+	DRM_DEBUG_DRIVER("Changing CDCLK to %dKHz\n", freq);
+
+	if (!skl_cdclk_wait_for_pcu_ready(dev_priv)) {
+		DRM_ERROR("failed to inform PCU about cdclk change\n");
+		return;
+	}
+
+	/* set CDCLK_CTL */
+	switch(freq) {
+	case 450000:
+	case 432000:
+		freq_select = CDCLK_FREQ_450_432;
+		pcu_ack = 1;
+		break;
+	case 540000:
+		freq_select = CDCLK_FREQ_540;
+		pcu_ack = 2;
+		break;
+	case 308570:
+	case 337500:
+	default:
+		freq_select = CDCLK_FREQ_337_308;
+		pcu_ack = 0;
+		break;
+	case 617140:
+	case 675000:
+		freq_select = CDCLK_FREQ_675_617;
+		pcu_ack = 3;
+		break;
+	}
+
+	I915_WRITE(CDCLK_CTL, freq_select | skl_cdclk_decimal(freq));
+	POSTING_READ(CDCLK_CTL);
+
+	/* inform PCU of the change */
+	mutex_lock(&dev_priv->rps.hw_lock);
+	sandybridge_pcode_write(dev_priv, SKL_PCODE_CDCLK_CONTROL, pcu_ack);
+	mutex_unlock(&dev_priv->rps.hw_lock);
+}
+
+void skl_uninit_cdclk(struct drm_i915_private *dev_priv)
+{
+	/* disable DBUF power */
+	I915_WRITE(DBUF_CTL, I915_READ(DBUF_CTL) & ~DBUF_POWER_REQUEST);
+	POSTING_READ(DBUF_CTL);
+
+	udelay(10);
+
+	if (I915_READ(DBUF_CTL) & DBUF_POWER_STATE)
+		DRM_ERROR("DBuf power disable timeout\n");
+
+	/* disable DPLL0 */
+	I915_WRITE(LCPLL1_CTL, I915_READ(LCPLL1_CTL) & ~LCPLL_PLL_ENABLE);
+	if (wait_for(!(I915_READ(LCPLL1_CTL) & LCPLL_PLL_LOCK), 1))
+		DRM_ERROR("Couldn't disable DPLL0\n");
+
+	intel_display_power_put(dev_priv, POWER_DOMAIN_PLLS);
+}
+
+void skl_init_cdclk(struct drm_i915_private *dev_priv)
+{
+	u32 val;
+	unsigned int required_vco;
+
+	/* enable PCH reset handshake */
+	val = I915_READ(HSW_NDE_RSTWRN_OPT);
+	I915_WRITE(HSW_NDE_RSTWRN_OPT, val | RESET_PCH_HANDSHAKE_ENABLE);
+
+	/* enable PG1 and Misc I/O */
+	intel_display_power_get(dev_priv, POWER_DOMAIN_PLLS);
+
+	/* DPLL0 already enabed !? */
+	if (I915_READ(LCPLL1_CTL) & LCPLL_PLL_ENABLE) {
+		DRM_DEBUG_DRIVER("DPLL0 already running\n");
+		return;
+	}
+
+	/* enable DPLL0 */
+	required_vco = skl_cdclk_get_vco(dev_priv->skl_boot_cdclk);
+	skl_dpll0_enable(dev_priv, required_vco);
+
+	/* set CDCLK to the frequency the BIOS chose */
+	skl_set_cdclk(dev_priv, dev_priv->skl_boot_cdclk);
+
+	/* enable DBUF power */
+	I915_WRITE(DBUF_CTL, I915_READ(DBUF_CTL) | DBUF_POWER_REQUEST);
+	POSTING_READ(DBUF_CTL);
+
+	udelay(10);
+
+	if (!(I915_READ(DBUF_CTL) & DBUF_POWER_STATE))
+		DRM_ERROR("DBuf power enable timeout\n");
+}
+
 /* returns HPLL frequency in kHz */
 static int valleyview_get_vco(struct drm_i915_private *dev_priv)
 {