Currently, gpt timer's clock is from ipg_per, and ipg_per clock is from ipg
on most of i.MX6 series SOCs, but ipg's rate may be scaled when system enters
low bus mode for saving power, then gpt timer's clock rate will be scaled as
well, as system timer should be kept stable and NOT drift, better to keep gpt
timer's clk at fixed rate, on i.MX6Q TO > 1.0, i.MX6DL and i.MX6SX, there is
OSC clk available for gpt timer, we should enable this feature, the hardware
design is as below:
i.MX6Q TO > 1.0: GPT_CR_CLKSRC, 3b'101 selects fix clock
of OSC / 8 for gpt per clk;
i.MX6DL and i.MX6SX: GPT_CR_CLKSRC, 3b'101 selects OSC
for gpt per clk, and we must enable GPT_CR_24MEM to
enable OSC clk source for gpt per, GPT_PR_PRESCALER24M
is for pre-scaling of this OSC clk, here set it to 8
to make gpt per clk is 3MHz;
i.MX6SL: ipg_per can be from OSC directly, so no need to
implement this new clk source for gpt per.
Anson Huang (3):
ARM: imx: add gpt_3m clk for i.mx6qdl
ARM: dts: imx6: change gpt per clk to gpt_3m on i.mx6qdl and i.mx6sx
ARM: imx: source gpt per clk from OSC for system timer
arch/arm/boot/dts/imx6qdl.dtsi | 2 +-
arch/arm/boot/dts/imx6sx.dtsi | 2 +-
arch/arm/mach-imx/clk-imx6q.c | 1 +
arch/arm/mach-imx/time.c | 29 ++++++++++++++++++++++++-----
include/dt-bindings/clock/imx6qdl-clock.h | 3 ++-
5 files changed, 29 insertions(+), 8 deletions(-)
--
1.7.9.5
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