[PATCH V2 0/3] move gpt per clk parent from ipg_per to OSC

[Anson Huang]

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.

As we still need to make it work on i.MX6Q TO1.0 which has no OSC clock source
for gpt per, so we add a soc_per clock for i.MX6Q, other SoCs all have OSC
clock source available for gpt per, so we can just replace the original gpt
per clk with gpt_3m clock.

Anson Huang (3):
  ARM: imx: add gpt_3m clk for i.mx6qdl
  ARM: dts: imx6: make gpt per clock can be from OSC
  ARM: imx: source gpt per clk from OSC for system timer

 arch/arm/boot/dts/imx6qdl.dtsi            |    5 ++--
 arch/arm/boot/dts/imx6sx.dtsi             |    2 +-
 arch/arm/mach-imx/clk-imx6q.c             |    1 +
 arch/arm/mach-imx/time.c                  |   41 ++++++++++++++++++++++++-----
 include/dt-bindings/clock/imx6qdl-clock.h |    3 ++-
 5 files changed, 42 insertions(+), 10 deletions(-)

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1.7.9.5