This is a note to let you know that I've just added the patch titled
clk: renesas: rzg2l: Fix computation formula
to the 6.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
clk-renesas-rzg2l-fix-computation-formula.patch
and it can be found in the queue-6.5 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit d576c761323b840ba0402c85a8b315e3e4dac593
Author: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
Date: Fri Sep 29 08:38:52 2023 +0300
clk: renesas: rzg2l: Fix computation formula
[ Upstream commit a2b23159499efd36b2d63b3c4534075d12ddc97a ]
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: ef3c613ccd68a ("clk: renesas: Add CPG core wrapper for RZ/G2L SoC")
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Link: https://lore.kernel.org/r/20230929053915.1530607-6-claudiu.beznea@xxxxxxxxxxxxxx
Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/clk/renesas/rzg2l-cpg.c b/drivers/clk/renesas/rzg2l-cpg.c
index 03028362cf619..a3b20c898a391 100644
--- a/drivers/clk/renesas/rzg2l-cpg.c
+++ b/drivers/clk/renesas/rzg2l-cpg.c
@@ -43,7 +43,7 @@
#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)
@@ -702,18 +702,18 @@ 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 = {
