i.MX25 GPT clock fix: ensure correct the clock source

Request for comment and commit.

From: T. Mehnert <t.mehnert@eckelmann.de>
Date: Mon, 4 Jul 2011 15:53:30 +0200
Subject: [PATCH] i.MX25 GPT clock fix: ensure correct the clock source

This patch ensures, that Linux will take the correct clock source (AHB_DIV)
for gpt in the ARM i.MX25 implementation. The currect code depends on the reset
defaults of the CCM_MCR register. So on some boards it could happen that the
UPLL is used for clock source, which results in faulty time behavior in Linux.
In this case all delays or sleeps will will be faktor 1.8 too long.
Signed-off-by: Torsten Mehnert <t.mehnert@eckelmann.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

arch/arm/mach-imx/clock-imx25.c

@@ -328,6 +328,9 @@ int __init mx25_clocks_init(void)
 	__raw_writel(__raw_readl(CRM_BASE+0x64) | (1 << 7) | (1 << 0),
 			CRM_BASE + 0x64);
 
+	/* Clock source for gpt is ahb_div */
+	__raw_writel(__raw_readl(CRM_BASE+0x64) & ~(1 << 5), CRM_BASE + 0x64);
+
 	mxc_timer_init(&gpt_clk, MX25_IO_ADDRESS(MX25_GPT1_BASE_ADDR), 54);
 
 	return 0;