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Commit 83b84c4e authored by Pavel Pisa's avatar Pavel Pisa Committed by Russell King
Browse files

[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: default avatarPavel Pisa <pisa@cmp.felk.cvut.cz>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent a45570eb

arch/arm/mach-imx/cpufreq.c

+6 −3
Original line number Original line Diff line number Diff line
@@ -50,6 +50,7 @@ 
#define CR_920T_ASYNC_MODE	0xC0000000

#define CR_920T_ASYNC_MODE	0xC0000000





static u32 mpctl0_at_boot;

static u32 mpctl0_at_boot;

static u32 bclk_div_at_boot;





static void imx_set_async_mode(void)

static void imx_set_async_mode(void)

{

{
@@ -182,7 +183,7 @@ static int imx_set_target(struct cpufreq_policy *policy, 
	unsigned long flags;

	unsigned long flags;

	long freq;

	long freq;

	long sysclk;

	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

	 * 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();

	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);

		freq = imx_compute_mpctl(&mpctl0, mpctl0_at_boot, freq, relation);

		if (freq < 0) {

		if (freq < 0) {

			printk(KERN_WARNING "imx: target frequency %ld Hz cannot be set\n", freq);

			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)

			if(bclk_div > 16)

				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;

		freq = (sysclk + bclk_div / 2) / bclk_div;

	}

	}
@@ -285,7 +288,7 @@ static struct cpufreq_driver imx_driver = { 




static int __init imx_cpufreq_init(void)

static int __init imx_cpufreq_init(void)

{

{



	bclk_div_at_boot = __mfld2val(CSCR_BCLK_DIV, CSCR) + 1;

	mpctl0_at_boot = 0;

	mpctl0_at_boot = 0;





	if((CSCR & CSCR_MPEN) &&

	if((CSCR & CSCR_MPEN) &&