linux-kernel - [PATCH 1/5] drm/msm/dsi_pll_10nm: Fix dividing the same numbers twice

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Date:   Sat,  9 Jan 2021 14:51:08 +0100
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>
To:     linux-arm-msm@...r.kernel.org
Cc:     konrad.dybcio@...ainline.org, marijn.suijten@...ainline.org,
        martin.botka@...ainline.org, phone-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org, robdclark@...il.com, sean@...rly.run,
        airlied@...ux.ie, daniel@...ll.ch, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>
Subject: [PATCH 1/5] drm/msm/dsi_pll_10nm: Fix dividing the same numbers twice

In function dsi_pll_calc_dec_frac we are calculating the decimal
div start parameter by dividing the decimal multiple by the
fractional multiplier: the remainder of that operation is stored
to then get programmed to the fractional divider registers of
the PLL.

It's useless to call div_u64_rem to get the remainder and *then*
call div_u64 to get the division result, as the first is already
giving that result: let's fix it by just caring about the result
of div_u64_rem.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...ainline.org>
---
 drivers/gpu/drm/msm/dsi/pll/dsi_pll_10nm.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/msm/dsi/pll/dsi_pll_10nm.c b/drivers/gpu/drm/msm/dsi/pll/dsi_pll_10nm.c
index 6ac04fc303f5..2c1fcf092ab8 100644
--- a/drivers/gpu/drm/msm/dsi/pll/dsi_pll_10nm.c
+++ b/drivers/gpu/drm/msm/dsi/pll/dsi_pll_10nm.c
@@ -172,9 +172,7 @@ static void dsi_pll_calc_dec_frac(struct dsi_pll_10nm *pll)
 
 	multiplier = 1 << config->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_freq <= 1900000000UL)
 		regs->pll_prop_gain_rate = 8;
-- 
2.29.2