clk: imx: lpcg-scu: SW workaround for errata (e10858)

[ Upstream commit 5ee063fa ]

Back-to-back LPCG writes can be ignored by the LPCG register due to
a HW bug. The writes need to be separated by at least 4 cycles of
the gated clock. See https://www.nxp.com.cn/docs/en/errata/IMX8_1N94W.pdf



The workaround is implemented as follows:
1. For clocks running greater than or equal to 24MHz, a read
followed by the write will provide sufficient delay.
2. For clocks running below 24MHz, add a delay of 4 clock cylces
after the write to the LPCG register.

Fixes: 2f77296d ("clk: imx: add lpcg clock support")
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Abel Vesa <abel.vesa@linaro.org>
Link: https://lore.kernel.org/r/20241027-imx-clk-v1-v3-1-89152574d1d7@nxp.com


Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>