I confess I never fully understood that previous calculation,
so this is not a "fix". But let's simplify this math
so poor brains like mine can read and make some sense of
it in the future.
v2: Don't follow the spec since that gives invalid
values and it is also confusing. This Ville's
version is much simpler.
v3: Use u64 cast instead of declaring a u64 dco. (Ville).
Cc: Ville Syrjälä <[email protected]>
Cc: Mika Kahola <[email protected]>
Cc: Manasi Navare <[email protected]>
Cc: James Ausmus <[email protected]>
Signed-off-by: Rodrigo Vivi <[email protected]>
---
drivers/gpu/drm/i915/intel_dpll_mgr.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_dpll_mgr.c
b/drivers/gpu/drm/i915/intel_dpll_mgr.c
index 361b7102b602..51c5ae4e9116 100644
--- a/drivers/gpu/drm/i915/intel_dpll_mgr.c
+++ b/drivers/gpu/drm/i915/intel_dpll_mgr.c
@@ -2153,6 +2153,8 @@ static void cnl_wrpll_params_populate(struct
skl_wrpll_params *params,
u32 dco_freq, u32 ref_freq,
int pdiv, int qdiv, int kdiv)
{
+ u32 dco;
+
switch (kdiv) {
case 1:
params->kdiv = 1;
@@ -2189,9 +2191,10 @@ static void cnl_wrpll_params_populate(struct
skl_wrpll_params *params,
params->qdiv_ratio = qdiv;
params->qdiv_mode = (qdiv == 1) ? 0 : 1;
- params->dco_integer = div_u64(dco_freq, ref_freq);
- params->dco_fraction = div_u64((div_u64((uint64_t)dco_freq<<15,
(uint64_t)ref_freq) -
- ((uint64_t)params->dco_integer<<15)) *
0x8000, 0x8000);
+ dco = div_u64((u64)dco_freq << 15, ref_freq);
+
+ params->dco_integer = dco >> 15;
+ params->dco_fraction = dco & 0x7fff;
}
static bool
--
2.13.6
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