From 8a00678a096445716861d2c0bd2a7007ad373f4d Mon Sep 17 00:00:00 2001 From: Rodrigo Vivi Date: Wed, 15 Nov 2017 10:42:57 -0800 Subject: [PATCH] drm/i915/cnl: Simplify dco_fraction calculation. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Cc: Mika Kahola Cc: Manasi Navare Cc: James Ausmus Signed-off-by: Rodrigo Vivi Reviewed-by: Ville Syrjälä Link: https://patchwork.freedesktop.org/patch/msgid/20171115184257.8633-1-rodrigo.vivi@intel.com --- 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 -- GitLab