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authorMatt Porter <mporter@ti.com>2012-05-07 16:49:21 +0000
committerAlbert ARIBAUD <albert.u.boot@aribaud.net>2012-05-15 08:31:41 +0200
commita3c3fabb0f65455068e01197e16927f0589beaa2 (patch)
tree1b6d04f49c674210f8f6e6abe83627d3d088b846 /arch/arm
parentc176dd0442c40d4e98c86848091f628707f9c50a (diff)
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arm, omap3: fix warm reset serial output on OMAP36xx/AM/DM37xx
In warm reset conditions on OMAP36xx/AM/DM37xx the rom code incorrectly sets the DPLL4 clock input divider to /6.5 which is an invalid value unless the input clock is 13MHz. When a JTAG emulator is attached, a warm reset is necessary after the emulator gains control of the process. This results in a loss of serial output due to the invalid DPLL4 settings. This patch fixes the issue by resetting the DPLL4 clock input divider to /1 when the input clock is not 13MHz. AM/DM37x TRM section 3.5.3.3.3.2.1 specifies that the /6.5 setting is only used when the input clock is 13MHz. Signed-off-by: Matt Porter <mporter@ti.com>
Diffstat (limited to 'arch/arm')
-rw-r--r--arch/arm/cpu/armv7/omap3/clock.c16
1 files changed, 16 insertions, 0 deletions
diff --git a/arch/arm/cpu/armv7/omap3/clock.c b/arch/arm/cpu/armv7/omap3/clock.c
index 567817e..09c51f6 100644
--- a/arch/arm/cpu/armv7/omap3/clock.c
+++ b/arch/arm/cpu/armv7/omap3/clock.c
@@ -572,6 +572,22 @@ void prcm_init(void)
}
if (get_cpu_family() == CPU_OMAP36XX) {
+ /*
+ * In warm reset conditions on OMAP36xx/AM/DM37xx
+ * the rom code incorrectly sets the DPLL4 clock
+ * input divider to /6.5. Section 3.5.3.3.3.2.1 of
+ * the AM/DM37x TRM explains that the /6.5 divider
+ * is used only when the input clock is 13MHz.
+ *
+ * If the part is in this cpu family *and* the input
+ * clock *is not* 13 MHz, then reset the DPLL4 clock
+ * input divider to /1 as it should never set to /6.5
+ * in this case.
+ */
+ if (sys_clkin_sel != 1) /* 13 MHz */
+ /* Bit 8: DPLL4_CLKINP_DIV */
+ sr32(&prm_base->clksrc_ctrl, 8, 1, 0);
+
/* Unlock MPU DPLL (slows things down, and needed later) */
sr32(&prcm_base->clken_pll_mpu, 0, 3, PLL_LOW_POWER_BYPASS);
wait_on_value(ST_MPU_CLK, 0, &prcm_base->idlest_pll_mpu,