On i.MX6Q TO > 1.0, i.MX6DL and i.MX6SX, gpt per clock
can be from OSC instead of ipg_per, as ipg_per's rate
may be scaled when system enter low bus mode, to keep
system timer NOT drift, better to make gpt per clock
at fixed rate, here add support for gpt per clock to
be from OSC which is at fixed rate always.
There are some difference on this implementation of
gpt per clock source, see below for details:
i.MX6Q TO > 1.0: GPT_CR_CLKSRC, b'101 selects fix clock
of OSC / 8 for gpt per clk;
i.MX6DL and i.MX6SX: GPT_CR_CLKSRC, b'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.
Signed-off-by: Anson Huang <b20788@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@freescale.com>
bad3db104f