regulator: s2mps11: Set default ramp delay for S2MPS11 LDOs

Driver did not provide default value for ramp delay for LDOs which lead
to warning in dmesg, e.g. on Odroid XU4:

[    1.486076] vdd_ldo9: ramp_delay not set
[    1.506875] vddq_mmc2: ramp_delay not set
[    1.523766] vdd_ldo15: ramp_delay not set
[    1.544702] vdd_sd: ramp_delay not set

The datasheet for all the S2MPS1x family is inconsistent here and does
not specify unambiguously the value of ramp delay for LDO. It mentions
30 mV/us in one timing diagram but then omits it completely in LDO
regulator characteristics table (it is specified for bucks).

However the vendor kernels for Galaxy S5 and Odroid XU3 use values of 12
mV/us or 24 mV/us.

Without the ramp delay value the consumers do not wait for voltage
settle after changing it. Although the proper value of ramp delay for
LDOs is unknown, it seems safer to use at least some value from
reference kernel than to leave it unset.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/mfd/samsung/core.h b/include/linux/mfd/samsung/core.h
index 6bc4bcd488ac..5a23dd4df432 100644
--- a/include/linux/mfd/samsung/core.h
+++ b/include/linux/mfd/samsung/core.h
@@ -30,6 +30,9 @@
 #define MIN_600_MV              600000
 #define MIN_500_MV              500000
 
+/* Ramp delay in uV/us */
+#define RAMP_DELAY_12_MVUS      12000
+
 /* Macros to represent steps for LDO/BUCK */
 #define STEP_50_MV              50000
 #define STEP_25_MV              25000