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: Gregory CLEMENT <gregory.clement@free-electrons.com>
Tested-by: Leigh Brown <leigh@solinno.co.uk>
Link: https://lkml.kernel.org/r/1409645719-20003-3-git-send-email-gregory.clement@free-electrons.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

1 files changed, 8 insertions, 0 deletions

diff --git a/drivers/clk/mvebu/armada-370.c b/drivers/clk/mvebu/armada-370.c
index bef198a83863..756f0f39d6a3 100644
--- a/drivers/clk/mvebu/armada-370.c
+++ b/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),
 };