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cubieboard: Keep AHB clock within specs 

The CPU was clocked at 384MHz in the bootblock, but the AHB bus has a
maximum rated frequency of 250MHz. Its clock needs to be divided to
keep it within spec. Overclocking the AHB bus hung the CPU when
memory was accessed.

Change-Id: I7cb9cdd1f126b3d5b0446fc68af79b54946bc2d3
Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-on: http://review.coreboot.org/4629
Tested-by: build bot (Jenkins)
Reviewed-by: David Hendricks <dhendrix@chromium.org>
This commit is contained in:
Alexandru Gagniuc 2013-12-26 02:02:00 -05:00
parent 30c20e92a2
commit 391622ae30
1 changed files with 4 additions and 2 deletions
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6
src/mainboard/cubietech/cubieboard/bootblock.c
View File

@ -15,7 +15,7 @@
#define CPU_AHB_APB0_DEFAULT \ #define CPU_AHB_APB0_DEFAULT \
CPU_CLK_SRC_OSC24M \ CPU_CLK_SRC_OSC24M \
| APB0_DIV_1 \ | APB0_DIV_1 \
| AHB_DIV_1 \ | AHB_DIV_2 \
| AXI_DIV_1 | AXI_DIV_1
#define GPH_STATUS_LEDS (1 << 20) | (1 << 21) #define GPH_STATUS_LEDS (1 << 20) | (1 << 21)
@ -33,7 +33,9 @@ static void cubieboard_set_sys_clock(void)
/* Switch CPU clock to main oscillator */ /* Switch CPU clock to main oscillator */
write32(CPU_AHB_APB0_DEFAULT, &ccm->cpu_ahb_apb0_cfg); write32(CPU_AHB_APB0_DEFAULT, &ccm->cpu_ahb_apb0_cfg);
/* Configure the PLL1. The value is the same one used by u-boot */ /* Configure the PLL1. The value is the same one used by u-boot
* P = 1, N = 16, K = 1, M = 1 --> Output = 384 MHz
*/
write32(0xa1005000, &ccm->pll1_cfg); write32(0xa1005000, &ccm->pll1_cfg);
/* FIXME: Delay to wait for PLL to lock */ /* FIXME: Delay to wait for PLL to lock */