drm/i915: Make M/N checks non-fuzzy

Now that we no longer fuzz M/N during fastset these should
match exctly.

In order to get a match with what the BIOS does we need to round
M/N down. And we do the opposite rounding when doing the readback.
That gets us pretty much the same thing back.

There can still be slight rounding differences between FDI M/N
vs. the DPLL output so we allow for tiny deviation in
intel_pipe_config_sanity_check().

v2: Tweak rounding/sanity check stuff a bit

Reviewed-by: Jani Nikula <jani.nikula@intel.com> #v1
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220907091057.11572-10-ville.syrjala@linux.intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index 0d068a2..1259c2e 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -4495,7 +4495,8 @@ int intel_dotclock_calculate(int link_freq,
        if (!m_n->link_n)
                return 0;
 
-       return div_u64(mul_u32_u32(m_n->link_m, link_freq), m_n->link_n);
+       return DIV_ROUND_UP_ULL(mul_u32_u32(m_n->link_m, link_freq),
+                               m_n->link_n);
 }
 
 int intel_crtc_dotclock(const struct intel_crtc_state *pipe_config)
@@ -5388,46 +5389,14 @@ bool intel_fuzzy_clock_check(int clock1, int clock2)
 }
 
 static bool
-intel_compare_m_n(unsigned int m, unsigned int n,
-                 unsigned int m2, unsigned int n2,
-                 bool exact)
-{
-       if (m == m2 && n == n2)
-               return true;
-
-       if (exact || !m || !n || !m2 || !n2)
-               return false;
-
-       BUILD_BUG_ON(DATA_LINK_M_N_MASK > INT_MAX);
-
-       if (n > n2) {
-               while (n > n2) {
-                       m2 <<= 1;
-                       n2 <<= 1;
-               }
-       } else if (n < n2) {
-               while (n < n2) {
-                       m <<= 1;
-                       n <<= 1;
-               }
-       }
-
-       if (n != n2)
-               return false;
-
-       return intel_fuzzy_clock_check(m, m2);
-}
-
-static bool
 intel_compare_link_m_n(const struct intel_link_m_n *m_n,
-                      const struct intel_link_m_n *m2_n2,
-                      bool exact)
+                      const struct intel_link_m_n *m2_n2)
 {
        return m_n->tu == m2_n2->tu &&
-               intel_compare_m_n(m_n->data_m, m_n->data_n,
-                                 m2_n2->data_m, m2_n2->data_n, exact) &&
-               intel_compare_m_n(m_n->link_m, m_n->link_n,
-                                 m2_n2->link_m, m2_n2->link_n, exact);
+               m_n->data_m == m2_n2->data_m &&
+               m_n->data_n == m2_n2->data_n &&
+               m_n->link_m == m2_n2->link_m &&
+               m_n->link_n == m2_n2->link_n;
 }
 
 static bool
@@ -5621,8 +5590,7 @@ intel_pipe_config_compare(const struct intel_crtc_state *current_config,
 
 #define PIPE_CONF_CHECK_M_N(name) do { \
        if (!intel_compare_link_m_n(&current_config->name, \
-                                   &pipe_config->name,\
-                                   !fastset)) { \
+                                   &pipe_config->name)) { \
                pipe_config_mismatch(fastset, crtc, __stringify(name), \
                                     "(expected tu %i data %i/%i link %i/%i, " \
                                     "found tu %i, data %i/%i link %i/%i)", \
@@ -5669,9 +5637,9 @@ intel_pipe_config_compare(const struct intel_crtc_state *current_config,
  */
 #define PIPE_CONF_CHECK_M_N_ALT(name, alt_name) do { \
        if (!intel_compare_link_m_n(&current_config->name, \
-                                   &pipe_config->name, !fastset) && \
+                                   &pipe_config->name) && \
            !intel_compare_link_m_n(&current_config->alt_name, \
-                                   &pipe_config->name, !fastset)) { \
+                                   &pipe_config->name)) { \
                pipe_config_mismatch(fastset, crtc, __stringify(name), \
                                     "(expected tu %i data %i/%i link %i/%i, " \
                                     "or tu %i data %i/%i link %i/%i, " \

diff --git a/drivers/gpu/drm/i915/display/intel_modeset_verify.c b/drivers/gpu/drm/i915/display/intel_modeset_verify.c
index a91586d..0736071 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_modeset_verify.c
+++ b/drivers/gpu/drm/i915/display/intel_modeset_verify.c
@@ -94,10 +94,10 @@ static void intel_pipe_config_sanity_check(struct drm_i915_private *dev_priv,
 
                /*
                 * FDI already provided one idea for the dotclock.
-                * Yell if the encoder disagrees.
+                * Yell if the encoder disagrees. Allow for slight
+                * rounding differences.
                 */
-               drm_WARN(&dev_priv->drm,
-                        !intel_fuzzy_clock_check(fdi_dotclock, dotclock),
+               drm_WARN(&dev_priv->drm, abs(fdi_dotclock - dotclock) > 1,
                         "FDI dotclock and encoder dotclock mismatch, fdi: %i, encoder: %i\n",
                         fdi_dotclock, dotclock);
        }