[PATCH V2] ARM: imx: improve the comment of CCM lpm SW workaround
From: Anson Huang
Date: Tue Dec 24 2013 - 05:21:48 EST
Improve the comment of SW workaround for CCM lpm issue using
hardware errata description to avoid confusion.
CCM: When improper low-power sequence is used, the SoC enters
low power mode before the ARM core executes WFI.
1) Software should trigger IRQ #32 (IOMUX) to be always pending
by setting IOMUX_GPR1_GINT.
2) Software should then unmask IRQ #32 in GPC before setting CCM
3) Software should mask IRQ #32 right after CCM Low-Power mode is
set (set bits 0-1 of CCM_CLPCR).
Signed-off-by: Anson Huang <b20788@xxxxxxxxxxxxx>
arch/arm/mach-imx/pm-imx6q.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/arch/arm/mach-imx/pm-imx6q.c b/arch/arm/mach-imx/pm-imx6q.c
index aecd9f8..31cb9d6 100644
@@ -156,10 +156,13 @@ int imx6q_set_lpm(enum mxc_cpu_pwr_mode mode)
- * Unmask the always pending IOMUXC interrupt #32 as wakeup source to
- * deassert dsm_request signal, so that we can ensure dsm_request
- * is not asserted when we're going to write CLPCR register to set LPM.
- * After setting up LPM bits, we need to mask this wakeup source.
+ * ERR007265:
+ * CCM: When improper low-power sequence is used, the SoC enters low power mode before the ARM core executes WFI.
+ * Software workaround:
+ * 1) Software should trigger IRQ #32 (IOMUX) to be always pending by setting IOMUX_GPR1_GINT.
+ * 2) Software should then unmask IRQ #32 in GPC before setting CCM Low-Power mode.
+ * 3) Software should mask IRQ #32 right after CCM Low-Power mode is set (set bits 0-1 of CCM_CLPCR).
iomuxc_irq_desc = irq_to_desc(32);
@@ -219,6 +222,8 @@ void __init imx6q_pm_init(void)
+ * This is for SW workaround step #1 of ERR007265, see comments
+ * in imx6q_set_lpm for details of this errata.
* Force IOMUXC irq pending, so that the interrupt to GPC can be
* used to deassert dsm_request signal when the signal gets
* asserted unexpectedly.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/