drm/i915: completely rewrite the Haswell PLL handling code

Problems with the previous code:
  - HDMI just uses WRPLL1 for everything, so dual head cases might not
    work sometimes.
  - At encoder->mode_set we just write the PLL register without doing
    any kind of check (e.g., check if the PLL is already being used).
  - There is no way to fail and return error codes at
    encoder->mode_set.
  - We write to PORT_CLK_SEL at mode_set and we never disable it.
  - Machines hang due to wrong clock enable/disable sequence.

So here we rewrite the code, making it a little more like the
pre-Haswell PLL mode set code:
  - Check PLL availability at ironlake_crtc_mode_set.
  - Try to use both WRPLLs.
  - Check if PLLs are used before actually trying to use them, and
    properly fail with error messages.
  - Enable/disable PORT_CLK_SEL at the right place.
  - Add some WARNs to check for bugs.

The next improvement will be to try to reuse PLLs if the timings
match, but this is content for another patch and it's already
documented with a TODO comment.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 7 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 7f05736c6d8a..9e446b621642 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -93,6 +93,12 @@ struct intel_pch_pll {
 };
 #define I915_NUM_PLLS 2
 
+struct intel_ddi_plls {
+        int spll_refcount;
+        int wrpll1_refcount;
+        int wrpll2_refcount;
+};
+
 /* Interface history:
  *
  * 1.1: Original.
@@ -812,6 +818,7 @@ typedef struct drm_i915_private {
         wait_queue_head_t pending_flip_queue;
 
         struct intel_pch_pll pch_plls[I915_NUM_PLLS];
+        struct intel_ddi_plls ddi_plls;
 
         /* Reclocking support */
         bool render_reclock_avail;