drm/msm/dsi: use mult_frac for pclk_bpp calculation

Simplify calculations around pixel_clk_rate division. Replace common
pattern of doing 64-bit multiplication and then a do_div() call with
simpler mult_frac() invocation.
Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/538273/
Link: https://lore.kernel.org/r/20230520200103.4019607-2-dmitry.baryshkov@linaro.orgSigned-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

drivers/gpu/drm/msm/dsi/dsi_host.c

@@ -585,7 +585,7 @@ unsigned long dsi_byte_clk_get_rate(struct mipi_dsi_host *host, bool is_bonded_d
 	u8 lanes = msm_host->lanes;
 	u32 bpp = dsi_get_bpp(msm_host->format);
 	unsigned long pclk_rate = dsi_get_pclk_rate(mode, is_bonded_dsi);
-	u64 pclk_bpp = (u64)pclk_rate * bpp;
+	unsigned long pclk_bpp;
 
 	if (lanes == 0) {
 		pr_err("%s: forcing mdss_dsi lanes to 1\n", __func__);
@@ -594,9 +594,9 @@ unsigned long dsi_byte_clk_get_rate(struct mipi_dsi_host *host, bool is_bonded_d
 
 	/* CPHY "byte_clk" is in units of 16 bits */
 	if (msm_host->cphy_mode)
-		do_div(pclk_bpp, (16 * lanes));
+		pclk_bpp = mult_frac(pclk_rate, bpp, 16 * lanes);
 	else
-		do_div(pclk_bpp, (8 * lanes));
+		pclk_bpp = mult_frac(pclk_rate, bpp, 8 * lanes);
 
 	return pclk_bpp;
 }
@@ -627,15 +627,12 @@ int dsi_calc_clk_rate_6g(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
 int dsi_calc_clk_rate_v2(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
 {
 	u32 bpp = dsi_get_bpp(msm_host->format);
-	u64 pclk_bpp;
 	unsigned int esc_mhz, esc_div;
 	unsigned long byte_mhz;
 
 	dsi_calc_pclk(msm_host, is_bonded_dsi);
 
-	pclk_bpp = (u64)msm_host->pixel_clk_rate * bpp;
-	do_div(pclk_bpp, 8);
-	msm_host->src_clk_rate = pclk_bpp;
+	msm_host->src_clk_rate = mult_frac(msm_host->pixel_clk_rate, bpp, 8);
 
 	/*
 	 * esc clock is byte clock followed by a 4 bit divider,