clk: meson: add ROUND_CLOSEST to the pll driver

Provide an option for the pll driver to round to the rate closest to the
requested rate, instead of systematically rounding down.

This may allow the provided rate to be closer to the requested rate when
rounding up is not an issue

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>

diff --git a/drivers/clk/meson/clk-pll.c b/drivers/clk/meson/clk-pll.c
index d58961f35b71bd12de327770e4d5963a3cea17ef..65a7bd9035516c4400cf57270dc1ba128cf964ec 100644 (file)
--- a/drivers/clk/meson/clk-pll.c
+++ b/drivers/clk/meson/clk-pll.c
@@ -105,7 +105,12 @@ static u16 __pll_params_with_frac(unsigned long rate,
        u64 val = (u64)rate * pllt->n;
 
        val <<= pllt->od + pllt->od2 + pllt->od3;
-       val = div_u64(val * frac_max, parent_rate);
+
+       if (pll->flags & CLK_MESON_PLL_ROUND_CLOSEST)
+               val = DIV_ROUND_CLOSEST_ULL(val * frac_max, parent_rate);
+       else
+               val = div_u64(val * frac_max, parent_rate);
+
        val -= pllt->m * frac_max;
 
        return min((u16)val, (u16)(frac_max - 1));
@@ -125,9 +130,13 @@ meson_clk_get_pll_settings(unsigned long rate,
        while (table[i].rate && table[i].rate <= rate)
                i++;
 
-       /* Select the setting of the rounded down rate */
-       if (i != 0)
-               i--;
+       if (i != 0) {
+               if (MESON_PARM_APPLICABLE(&pll->frac) ||
+                   !(pll->flags & CLK_MESON_PLL_ROUND_CLOSEST) ||
+                   (abs(rate - table[i - 1].rate) <
+                    abs(rate - table[i].rate)))
+                       i--;
+       }
 
        return (struct pll_rate_table *)&table[i];
 }

diff --git a/drivers/clk/meson/clkc.h b/drivers/clk/meson/clkc.h
index 9cdcd9b6c16cba08d5299407bd61693b99e853ae..8fe73c4edca8ef091da760b42402eb33395cca48 100644 (file)
--- a/drivers/clk/meson/clkc.h
+++ b/drivers/clk/meson/clkc.h
@@ -71,6 +71,8 @@ struct pll_rate_table {
                .od             = (_od),                                \
        }
 
+#define CLK_MESON_PLL_ROUND_CLOSEST    BIT(0)
+
 struct meson_clk_pll_data {
        struct parm m;
        struct parm n;