drm/i915: Make data/link N value power of two
The BIOS uses power of two values for the data/link N value.
Follow suit to make the Zotac DP to dual-HDMI dongle work.
v2: Clean up the magic numbers and defines
Change the N clamping to be a bit easier on the eye
Rename intel_reduce_ratio to intel_reduce_m_n_ratio
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=49402
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=59810
Tested-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 6e423e0..efe8299 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -4084,26 +4084,36 @@
}
static void
-intel_reduce_ratio(uint32_t *num, uint32_t *den)
+intel_reduce_m_n_ratio(uint32_t *num, uint32_t *den)
{
- while (*num > 0xffffff || *den > 0xffffff) {
+ while (*num > DATA_LINK_M_N_MASK ||
+ *den > DATA_LINK_M_N_MASK) {
*num >>= 1;
*den >>= 1;
}
}
+static void compute_m_n(unsigned int m, unsigned int n,
+ uint32_t *ret_m, uint32_t *ret_n)
+{
+ *ret_n = min_t(unsigned int, roundup_pow_of_two(n), DATA_LINK_N_MAX);
+ *ret_m = div_u64((uint64_t) m * *ret_n, n);
+ intel_reduce_m_n_ratio(ret_m, ret_n);
+}
+
void
intel_link_compute_m_n(int bits_per_pixel, int nlanes,
int pixel_clock, int link_clock,
struct intel_link_m_n *m_n)
{
m_n->tu = 64;
- m_n->gmch_m = bits_per_pixel * pixel_clock;
- m_n->gmch_n = link_clock * nlanes * 8;
- intel_reduce_ratio(&m_n->gmch_m, &m_n->gmch_n);
- m_n->link_m = pixel_clock;
- m_n->link_n = link_clock;
- intel_reduce_ratio(&m_n->link_m, &m_n->link_n);
+
+ compute_m_n(bits_per_pixel * pixel_clock,
+ link_clock * nlanes * 8,
+ &m_n->gmch_m, &m_n->gmch_n);
+
+ compute_m_n(pixel_clock, link_clock,
+ &m_n->link_m, &m_n->link_n);
}
static inline bool intel_panel_use_ssc(struct drm_i915_private *dev_priv)