[PATCH 2/2] sunxi: sun50i_h6: clock: fix PLL_PERIPH0 rate calculation

[Andre Przywara <andre.przywara@arm.com>]

On the Allwinner D1/R528/T113-s3 SoCs (NCAT2) the factors encoded in
the PLL register describe the doubled clock rate, as in the other SoCs.

Correct for that by always dividing the calculated rate by 2, except on
the H6, where we need a divisor of 4 (no change here).

This corrects the PERIPH0 clock rate as read by the MMC driver, and
actually doubles the MMC performance on those NCAT2 chips.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reported-by: Kuba Szczodrzyński <kuba@szczodrzynski.pl>
---
 arch/arm/mach-sunxi/clock_sun50i_h6.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/arch/arm/mach-sunxi/clock_sun50i_h6.c b/arch/arm/mach-sunxi/clock_sun50i_h6.c
index b424a7893ea..359513d1669 100644
--- a/arch/arm/mach-sunxi/clock_sun50i_h6.c
+++ b/arch/arm/mach-sunxi/clock_sun50i_h6.c
@@ -147,15 +147,20 @@ unsigned int clock_get_pll6(void)
 	if (IS_ENABLED(CONFIG_SUNXI_GEN_NCAT2)) {
 		div1 = ((rval & CCM_PLL6_CTRL_P0_MASK) >>
 			CCM_PLL6_CTRL_P0_SHIFT) + 1;
-		m = 1;
 	} else {
 		div1 = ((rval & CCM_PLL6_CTRL_DIV1_MASK) >>
 			CCM_PLL6_CTRL_DIV1_SHIFT) + 1;
-		if (IS_ENABLED(CONFIG_MACH_SUN50I_H6))
-			m = 4;
-		else
-			m = 2;
 	}
 
+	/*
+	 * The factors encoded in the register describe the doubled clock
+	 * frequency, expect for the H6, where it's the quadrupled frequency.
+	 * Compensate for that here.
+	 */
+	if (IS_ENABLED(CONFIG_MACH_SUN50I_H6))
+		m = 4;
+	else
+		m = 2;
+
 	return 24000000U * n / m / div1 / div2;
 }
-- 
2.25.1