UbiquitousOS
/
OpenCloudOS-Kernel
mirror of https://gitee.com/OpenCloudOS/OpenCloudOS-Kernel.git
11
0
Fork 0
Code Issues Projects Releases Wiki Activity

[ARM] 4254/1: i.MX/MX1 CPU Frequency scaling honor boot loader set BCLK_DIV. 

The minimal bus clock prescaler should be kept at value
selected by the board / boot loader designer.
Switching frequency above startup limit could
lead to the external memory/devices misbehave.

Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Pavel Pisa 2007-03-07 23:52:40 +01:00 committed by Russell King
parent a45570ebf3
commit 83b84c4e8c
1 changed files with 6 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
arch/arm/mach-imx/cpufreq.c
View File

@ -50,6 +50,7 @@
#define CR_920T_ASYNC_MODE 0xC0000000
static u32 mpctl0_at_boot;
static u32 bclk_div_at_boot;
static void imx_set_async_mode(void)
{
@ -182,7 +183,7 @@ static int imx_set_target(struct cpufreq_policy *policy,
unsigned long flags;
long freq;
long sysclk;
unsigned int bclk_div = 1;
unsigned int bclk_div = bclk_div_at_boot;
/*
* Some governors do not respects CPU and policy lower limits
@ -202,7 +203,7 @@ static int imx_set_target(struct cpufreq_policy *policy,
sysclk = imx_get_system_clk();
if (freq > sysclk + 1000000) {
if (freq > sysclk / bclk_div_at_boot + 1000000) {
freq = imx_compute_mpctl(&mpctl0, mpctl0_at_boot, freq, relation);
if (freq < 0) {
printk(KERN_WARNING "imx: target frequency %ld Hz cannot be set\n", freq);
@ -217,6 +218,8 @@ static int imx_set_target(struct cpufreq_policy *policy,
if(bclk_div > 16)
bclk_div = 16;
if(bclk_div < bclk_div_at_boot)
bclk_div = bclk_div_at_boot;
}
freq = (sysclk + bclk_div / 2) / bclk_div;
}
@ -285,7 +288,7 @@ static struct cpufreq_driver imx_driver = {
static int __init imx_cpufreq_init(void)
{
bclk_div_at_boot = __mfld2val(CSCR_BCLK_DIV, CSCR) + 1;
mpctl0_at_boot = 0;
if((CSCR & CSCR_MPEN) &&