Re: [PATCH] drm/msm/dsi: Use division result from div_u64_rem in 7nm and 14nm PLL

From: abhinavk
Date: Tue Sep 07 2021 - 18:58:59 EST


On 2021-09-06 13:25, Marijn Suijten wrote:
div_u64_rem provides the result of the divison and additonally the
remainder; don't use this function to solely calculate the remainder
while calculating the division again with div_u64.

A similar improvement was applied earlier to the 10nm pll in
5c191fef4ce2 ("drm/msm/dsi_pll_10nm: Fix dividing the same numbers
twice").

Signed-off-by: Marijn Suijten <marijn.suijten@xxxxxxxxxxxxxx>
Reviewed-by: Abhinav Kumar <abhinavk@xxxxxxxxxxxxxx>
---
drivers/gpu/drm/msm/dsi/phy/dsi_phy_14nm.c | 4 +---
drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c | 4 +---
2 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_14nm.c
b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_14nm.c
index 3c1e2106d962..8905f365c932 100644
--- a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_14nm.c
+++ b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_14nm.c
@@ -213,9 +213,7 @@ static void pll_14nm_dec_frac_calc(struct
dsi_pll_14nm *pll, struct dsi_pll_conf
DBG("vco_clk_rate=%lld ref_clk_rate=%lld", vco_clk_rate, fref);

dec_start_multiple = div_u64(vco_clk_rate * multiplier, fref);
- div_u64_rem(dec_start_multiple, multiplier, &div_frac_start);
-
- dec_start = div_u64(dec_start_multiple, multiplier);
+ dec_start = div_u64_rem(dec_start_multiple, multiplier, &div_frac_start);

pconf->dec_start = (u32)dec_start;
pconf->div_frac_start = div_frac_start;
diff --git a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c
b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c
index c77c30628cca..1a5abbd9fb76 100644
--- a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c
+++ b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c
@@ -114,9 +114,7 @@ static void dsi_pll_calc_dec_frac(struct
dsi_pll_7nm *pll, struct dsi_pll_config

multiplier = 1 << FRAC_BITS;
dec_multiple = div_u64(pll_freq * multiplier, divider);
- div_u64_rem(dec_multiple, multiplier, &frac);
-
- dec = div_u64(dec_multiple, multiplier);
+ dec = div_u64_rem(dec_multiple, multiplier, &frac);

if (!(pll->phy->cfg->quirks & DSI_PHY_7NM_QUIRK_V4_1))
config->pll_clock_inverters = 0x28;