[PATCH 5.3 190/193] clk: imx8m: Use SYS_PLL1_800M as intermediate parent of CLK_ARM

[Greg Kroah-Hartman]

From: Leonard Crestez <leonard.crestez@xxxxxxx>

[ Upstream commit b234fe9558615098d8d62516e7041ad7f99ebcea ]

During cpu frequency switching the main "CLK_ARM" is reparented to an
intermediate "step" clock. On imx8mm and imx8mn the 24M oscillator is
used for this purpose but it is extremely slow, increasing wakeup
latencies to the point that i2c transactions can timeout and system
becomes unresponsive.

Fix by switching the "step" clk to SYS_PLL1_800M, matching the behavior
of imx8m cpufreq drivers in imx vendor tree.

This bug was not immediately apparent because upstream arm64 defconfig
uses the "performance" governor by default so no cpufreq transitions
happen.

Fixes: ba5625c3e272 ("clk: imx: Add clock driver support for imx8mm")
Fixes: 96d6392b54db ("clk: imx: Add support for i.MX8MN clock driver")

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Leonard Crestez <leonard.crestez@xxxxxxx>
Link: https://lkml.kernel.org/r/f5d2b9c53f1ed5ccb1dd3c6624f56759d92e1689.1571771777.git.leonard.crestez@xxxxxxx
Acked-by: Shawn Guo <shawnguo@xxxxxxxxxx>
Signed-off-by: Stephen Boyd <sboyd@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/clk/imx/clk-imx8mm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clk/imx/clk-imx8mm.c b/drivers/clk/imx/clk-imx8mm.c
index 6f46bcb1d6432..59ce93691e970 100644
--- a/drivers/clk/imx/clk-imx8mm.c
+++ b/drivers/clk/imx/clk-imx8mm.c
@@ -666,7 +666,7 @@ static int __init imx8mm_clocks_init(struct device_node *ccm_node)
 					   clks[IMX8MM_CLK_A53_DIV],
 					   clks[IMX8MM_CLK_A53_SRC],
 					   clks[IMX8MM_ARM_PLL_OUT],
-					   clks[IMX8MM_CLK_24M]);
+					   clks[IMX8MM_SYS_PLL1_800M]);
 
 	imx_check_clocks(clks, ARRAY_SIZE(clks));
 
-- 
2.20.1