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clk: renesas: rzg2l: Fix computation formula

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[ Upstream commit a2b2315949 ]

According to the hardware manual for RZ/G2L
(r01uh0914ej0130-rzg2l-rzg2lc.pdf), the computation formula for PLL rate
is as follows:

    Fout = ((m + k/65536) * Fin) / (p * 2^s)

and k has values in the range [-32768, 32767].  Dividing k by 65536 with
integer arithmetic gives zero all the time, causing slight differences
b/w what has been set vs. what is displayed.  Thus, get rid of this and
decompose the formula before dividing k by 65536.

Fixes: ef3c613ccd ("clk: renesas: Add CPG core wrapper for RZ/G2L SoC")
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20230929053915.1530607-6-claudiu.beznea@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Claudiu Beznea 2023-09-29 08:38:52 +03:00 committed by Greg Kroah-Hartman
parent da8862f717
commit a8454ab79e
1 changed files with 6 additions and 6 deletions
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12
drivers/clk/renesas/rzg2l-cpg.c
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@ -42,7 +42,7 @@
#define GET_SHIFT(val) ((val >> 12) & 0xff)
#define GET_WIDTH(val) ((val >> 8) & 0xf)
#define KDIV(val) FIELD_GET(GENMASK(31, 16), val)
#define KDIV(val) ((s16)FIELD_GET(GENMASK(31, 16), val))
#define MDIV(val) FIELD_GET(GENMASK(15, 6), val)
#define PDIV(val) FIELD_GET(GENMASK(5, 0), val)
#define SDIV(val) FIELD_GET(GENMASK(2, 0), val)
@ -695,18 +695,18 @@ static unsigned long rzg2l_cpg_pll_clk_recalc_rate(struct clk_hw *hw,
struct pll_clk *pll_clk = to_pll(hw);
struct rzg2l_cpg_priv *priv = pll_clk->priv;
unsigned int val1, val2;
unsigned int mult = 1;
unsigned int div = 1;
u64 rate;
if (pll_clk->type != CLK_TYPE_SAM_PLL)
return parent_rate;
val1 = readl(priv->base + GET_REG_SAMPLL_CLK1(pll_clk->conf));
val2 = readl(priv->base + GET_REG_SAMPLL_CLK2(pll_clk->conf));
mult = MDIV(val1) + KDIV(val1) / 65536;
div = PDIV(val1) << SDIV(val2);
return DIV_ROUND_CLOSEST_ULL((u64)parent_rate * mult, div);
rate = mul_u64_u32_shr(parent_rate, (MDIV(val1) << 16) + KDIV(val1),
16 + SDIV(val2));
return DIV_ROUND_CLOSEST_ULL(rate, PDIV(val1));
}
static const struct clk_ops rzg2l_cpg_pll_ops = {