drm/i915: Tightly scope intel_encoder to prevent invalid use

We reset intel_encoder for every matching encoder whilst iterating over
the encoders attached to this crtc when changing mode. As such in a
cloned configuration intel_encoder may not correspond to the correct
is_edp encoder.

By scoping intel_encoder to the loop, not only is the compiler able to
spot this mistake, we also improve readiability for ourselves.
[It might not be a mistake, within this function it is unclear as to
whether it is permissable for eDP to be cloned...]

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

1 files changed, 12 insertions, 13 deletions

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 83c85450608e..0b90443f1eb3 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -3508,10 +3508,9 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
         u32 dpll = 0, fp = 0, fp2 = 0, dspcntr, pipeconf;
         bool ok, has_reduced_clock = false, is_sdvo = false, is_dvo = false;
         bool is_crt = false, is_lvds = false, is_tv = false, is_dp = false;
-        bool is_edp = false;
+        struct intel_encoder *has_edp_encoder = NULL;
         struct drm_mode_config *mode_config = &dev->mode_config;
         struct drm_encoder *encoder;
-        struct intel_encoder *intel_encoder = NULL;
         const intel_limit_t *limit;
         int ret;
         struct fdi_m_n m_n = {0};
@@ -3532,12 +3531,12 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
         drm_vblank_pre_modeset(dev, pipe);
 
         list_for_each_entry(encoder, &mode_config->encoder_list, head) {
+                struct intel_encoder *intel_encoder;
 
-                if (!encoder || encoder->crtc != crtc)
+                if (encoder->crtc != crtc)
                         continue;
 
                 intel_encoder = enc_to_intel_encoder(encoder);
-
                 switch (intel_encoder->type) {
                 case INTEL_OUTPUT_LVDS:
                         is_lvds = true;
@@ -3561,7 +3560,7 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
                         is_dp = true;
                         break;
                 case INTEL_OUTPUT_EDP:
-                        is_edp = true;
+                        has_edp_encoder = intel_encoder;
                         break;
                 }
 
@@ -3639,10 +3638,10 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
                 int lane = 0, link_bw, bpp;
                 /* eDP doesn't require FDI link, so just set DP M/N
                    according to current link config */
-                if (is_edp) {
+                if (has_edp_encoder) {
                         target_clock = mode->clock;
-                        intel_edp_link_config(intel_encoder,
-                                        &lane, &link_bw);
+                        intel_edp_link_config(has_edp_encoder,
+                                              &lane, &link_bw);
                 } else {
                         /* DP over FDI requires target mode clock
                            instead of link clock */
@@ -3663,7 +3662,7 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
                                 temp |= PIPE_8BPC;
                         else
                                 temp |= PIPE_6BPC;
-                } else if (is_edp || (is_dp && intel_pch_has_edp(crtc))) {
+                } else if (has_edp_encoder || (is_dp && intel_pch_has_edp(crtc))) {
                         switch (dev_priv->edp_bpp/3) {
                         case 8:
                                 temp |= PIPE_8BPC;
@@ -3736,7 +3735,7 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
 
                 udelay(200);
 
-                if (is_edp) {
+                if (has_edp_encoder) {
                         if (dev_priv->lvds_use_ssc) {
                                 temp |= DREF_SSC1_ENABLE;
                                 I915_WRITE(PCH_DREF_CONTROL, temp);
@@ -3885,7 +3884,7 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
                 dpll_reg = pch_dpll_reg;
         }
 
-        if (!is_edp) {
+        if (!has_edp_encoder) {
                 I915_WRITE(fp_reg, fp);
                 I915_WRITE(dpll_reg, dpll & ~DPLL_VCO_ENABLE);
                 I915_READ(dpll_reg);
@@ -3980,7 +3979,7 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
                 }
         }
 
-        if (!is_edp) {
+        if (!has_edp_encoder) {
                 I915_WRITE(fp_reg, fp);
                 I915_WRITE(dpll_reg, dpll);
                 I915_READ(dpll_reg);
@@ -4059,7 +4058,7 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
                 I915_WRITE(link_m1_reg, m_n.link_m);
                 I915_WRITE(link_n1_reg, m_n.link_n);
 
-                if (is_edp) {
+                if (has_edp_encoder) {
                         ironlake_set_pll_edp(crtc, adjusted_mode->clock);
                 } else {
                         /* enable FDI RX PLL too */