drm/i915: Avoid use of uninitialised values when disabling panel-fitter

We were passing garbage values into the panel-fitter control register
when disabling it on Ironlake - those values (filter modes and reserved
MBZ bits) would have then be re-used the next time panel-fitting was
enabled.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 15 insertions, 20 deletions

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 1bd0c672ec90..cf8d5e5a286e 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -1865,9 +1865,6 @@ static void ironlake_crtc_dpms(struct drm_crtc *crtc, int mode)
         int fdi_tx_reg = (pipe == 0) ? FDI_TXA_CTL : FDI_TXB_CTL;
         int fdi_rx_reg = (pipe == 0) ? FDI_RXA_CTL : FDI_RXB_CTL;
         int transconf_reg = (pipe == 0) ? TRANSACONF : TRANSBCONF;
-        int pf_ctl_reg = (pipe == 0) ? PFA_CTL_1 : PFB_CTL_1;
-        int pf_win_size = (pipe == 0) ? PFA_WIN_SZ : PFB_WIN_SZ;
-        int pf_win_pos = (pipe == 0) ? PFA_WIN_POS : PFB_WIN_POS;
         int cpu_htot_reg = (pipe == 0) ? HTOTAL_A : HTOTAL_B;
         int cpu_hblank_reg = (pipe == 0) ? HBLANK_A : HBLANK_B;
         int cpu_hsync_reg = (pipe == 0) ? HSYNC_A : HSYNC_B;
@@ -1936,15 +1933,19 @@ static void ironlake_crtc_dpms(struct drm_crtc *crtc, int mode)
                 }
 
                 /* Enable panel fitting for LVDS */
-                if (intel_pipe_has_type(crtc, INTEL_OUTPUT_LVDS)
-                    || HAS_eDP || intel_pch_has_edp(crtc)) {
-                        if (dev_priv->pch_pf_size) {
-                                temp = I915_READ(pf_ctl_reg);
-                                I915_WRITE(pf_ctl_reg, temp | PF_ENABLE | PF_FILTER_MED_3x3);
-                                I915_WRITE(pf_win_pos, dev_priv->pch_pf_pos);
-                                I915_WRITE(pf_win_size, dev_priv->pch_pf_size);
-                        } else
-                                I915_WRITE(pf_ctl_reg, temp & ~PF_ENABLE);
+                if (dev_priv->pch_pf_size &&
+                    (intel_pipe_has_type(crtc, INTEL_OUTPUT_LVDS)
+                    || HAS_eDP || intel_pch_has_edp(crtc))) {
+                        /* Force use of hard-coded filter coefficients
+                         * as some pre-programmed values are broken,
+                         * e.g. x201.
+                         */
+                        I915_WRITE(pipe ? PFB_CTL_1 : PFA_CTL_1,
+                                   PF_ENABLE | PF_FILTER_MED_3x3);
+                        I915_WRITE(pipe ? PFB_WIN_POS : PFA_WIN_POS,
+                                   dev_priv->pch_pf_pos);
+                        I915_WRITE(pipe ? PFB_WIN_SZ : PFA_WIN_SZ,
+                                   dev_priv->pch_pf_size);
                 }
 
                 /* Enable CPU pipe */
@@ -2109,14 +2110,8 @@ static void ironlake_crtc_dpms(struct drm_crtc *crtc, int mode)
                 udelay(100);
 
                 /* Disable PF */
-                temp = I915_READ(pf_ctl_reg);
-                if ((temp & PF_ENABLE) != 0) {
-                        I915_WRITE(pf_ctl_reg, temp & ~PF_ENABLE);
-                        I915_READ(pf_ctl_reg);
-                }
-                I915_WRITE(pf_win_size, 0);
-                POSTING_READ(pf_win_size);
-
+                I915_WRITE(pipe ? PFB_CTL_1 : PFA_CTL_1, 0);
+                I915_WRITE(pipe ? PFB_WIN_SZ : PFA_WIN_SZ, 0);
 
                 /* disable CPU FDI tx and PCH FDI rx */
                 temp = I915_READ(fdi_tx_reg);