ARM: imx: improve the comment of CCM lpm SW workaround
Improve the comment of SW workaround for CCM lpm issue using
hardware errata description to avoid confusion.
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).
Signed-off-by: Anson Huang <b20788@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
diff --git a/arch/arm/mach-imx/pm-imx6q.c b/arch/arm/mach-imx/pm-imx6q.c
index aecd9f8..9d47adc 100644
--- a/arch/arm/mach-imx/pm-imx6q.c
+++ b/arch/arm/mach-imx/pm-imx6q.c
@@ -156,10 +156,16 @@
}
/*
- * 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);
imx_gpc_irq_unmask(&iomuxc_irq_desc->irq_data);
@@ -219,6 +225,8 @@
WARN_ON(!ccm_base);
/*
+ * 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.