sunxi: Add CONFIG_OLD_SUNXI_KERNEL_COMPAT Kconfig option

Add a Kconfig option which users can select when they want to boot older
kernels, e.g. the linux-sunxi 3.4 kernels. For now this just forces the pll5
"p" value to 1 (divide by 2) as that is what those kernels are hardcoded too,
in the future this may enable further workarounds.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Tom Rini <trini@ti.com>
--
Changes in v2:
-s/CONFIG_OLD_KERNEL_COMPAT/CONFIG_OLD_SUNXI_KERNEL_COMPAT.
-Move the code block setting P(1) for old kernels to where P gets cleared

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/arm/cpu/armv7/sunxi/dram.c b/arch/arm/cpu/armv7/sunxi/dram.c
index 0cbcf5767c..3cf3cbf19a 100644
--- a/arch/arm/cpu/armv7/sunxi/dram.c
+++ b/arch/arm/cpu/armv7/sunxi/dram.c
@@ -262,6 +262,10 @@ static void mctl_setup_dram_clock(u32 clk, u32 mbus_clk)
 	reg_val &= ~CCM_PLL5_CTRL_K_MASK;		/* set K to 0 (x1) */
 	reg_val &= ~CCM_PLL5_CTRL_N_MASK;		/* set N to 0 (x0) */
 	reg_val &= ~CCM_PLL5_CTRL_P_MASK;		/* set P to 0 (x1) */
+#ifdef CONFIG_OLD_SUNXI_KERNEL_COMPAT
+	/* Old kernels are hardcoded to P=1 (divide by 2) */
+	reg_val |= CCM_PLL5_CTRL_P(1);
+#endif
 	if (clk >= 540 && clk < 552) {
 		/* dram = 540MHz */
 		reg_val |= CCM_PLL5_CTRL_M(CCM_PLL5_CTRL_M_X(2));