[U-Boot] mx53: Turn off child clocks before reconfigure perclk_root

Message ID 1319479680-31380-1-git-send-email-fabio.estevam@freescale.com
State Accepted
Commit 41c881c0caed2dd0cc6824ad7b355e15e6c410cd
Delegated to: Stefano Babic
Headers show

Commit Message

Fabio Estevam Oct. 24, 2011, 6:08 p.m.
In addition to ensuring that PERCLK remains at least 2.5 times slower
than the AHB clock, certain steps need to be followed to ensure robust
operation of PERCLK when reconfiguring the PERCLK clock source.

To properly configure the PERCLK clock source, the following steps are

1.In the CCGR registers, gate the clocks to all PERCLK-dependent
2.Select the desired input clock for the PERCLK root clock (to be either
  source from the peripherals main source clock or the
  lp_apm clock source). Refer to the CMCBR register,  perclk_lp_apm_sel bit.
3.Configure the perclk_pred1, perclk_pred2, and perclk_podf dividers
  to the desired setting.  Refer to the CBCDR register for details.
4.In the CCGR registers, enable the desired clocks for the
  PERCLK-dependent module clocks.

If these steps aren't followed, GPT timer may stop and the kernel stops
at "Calibrating delay loop".

Signed-off-by: Terry Lv <r65388@freescale.com>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
 arch/arm/cpu/armv7/mx5/lowlevel_init.S |   15 +++++++++++++++
 1 files changed, 15 insertions(+), 0 deletions(-)


diff --git a/arch/arm/cpu/armv7/mx5/lowlevel_init.S b/arch/arm/cpu/armv7/mx5/lowlevel_init.S
index 7e37221..01f6d75 100644
--- a/arch/arm/cpu/armv7/mx5/lowlevel_init.S
+++ b/arch/arm/cpu/armv7/mx5/lowlevel_init.S
@@ -180,6 +180,21 @@ 
 1:	ldr r1, [r0, #CLKCTL_CDHIPR]
 	cmp r1, #0x0
 	bne 1b
+	ldr r1, =0x3FFFFFFF
+	str r1, [r0, #CLKCTL_CCGR0]
+	ldr r1, =0x0
+	str r1, [r0, #CLKCTL_CCGR1]
+	str r1, [r0, #CLKCTL_CCGR2]
+	str r1, [r0, #CLKCTL_CCGR3]
+	str r1, [r0, #CLKCTL_CCGR7]
+	ldr r1, =0x00030000
+	str r1, [r0, #CLKCTL_CCGR4]
+	ldr r1, =0x00FFF030
+	str r1, [r0, #CLKCTL_CCGR5]
+	ldr r1, =0x0F00030F
+	str r1, [r0, #CLKCTL_CCGR6]
 	/* Switch ARM to step clock */