clk: mvebu: armada-370: Fix timer drift caused by the SSCG deviation

This commit activates the SSCG deviation correction for the Armada
370. It uses the optional function introduced by the commit "clk:
mvebu: Fix clk frequency value if SSCG is enabled".

Without this fix the deviation measured on a Mirabox was of a few
second each hour, whereas with this fix it was reduced at around
50ppm (around 4s per day).
Signed-off-by: NGregory CLEMENT <gregory.clement@free-electrons.com>
Tested-by: NLeigh Brown <leigh@solinno.co.uk>
Link: https://lkml.kernel.org/r/1409645719-20003-3-git-send-email-gregory.clement@free-electrons.comSigned-off-by: NJason Cooper <jason@lakedaemon.net>

drivers/clk/mvebu/armada-370.c

@@ -23,6 +23,7 @@
  */
 
 #define SARL				0	/* Low part [0:31] */
+#define	 SARL_A370_SSCG_ENABLE		BIT(10)
 #define	 SARL_A370_PCLK_FREQ_OPT	11
 #define	 SARL_A370_PCLK_FREQ_OPT_MASK	0xF
 #define	 SARL_A370_FAB_FREQ_OPT		15
@@ -133,10 +134,17 @@ static void __init a370_get_clk_ratio(
 	}
 }
 
+static bool a370_is_sscg_enabled(void __iomem *sar)
+{
+	return !(readl(sar) & SARL_A370_SSCG_ENABLE);
+}
+
 static const struct coreclk_soc_desc a370_coreclks = {
 	.get_tclk_freq = a370_get_tclk_freq,
 	.get_cpu_freq = a370_get_cpu_freq,
 	.get_clk_ratio = a370_get_clk_ratio,
+	.is_sscg_enabled = a370_is_sscg_enabled,
+	.fix_sscg_deviation = kirkwood_fix_sscg_deviation,
 	.ratios = a370_coreclk_ratios,
 	.num_ratios = ARRAY_SIZE(a370_coreclk_ratios),
 };