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ARM: imx: ensure dsm_request signal is not asserted when setting LPM

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There is a defect in imx6 LPM design.  When SW tries to enter low power
mode with following sequence, the chip will enter low power mode before
A9 CPU execute WFI instruction:

1. Set CCM_CLPCR[1:0] to 2'b00;
2. ARM CPU enters WFI;
3. ARM CPU wakeup from an interrupt event, which is masked by GPC or not
   visible to GPC, such as interrupt from local timer;
4. Set CCM_CLPCR[1:0] to 2'b01 or 2'b10;
5. ARM CPU execute WFI.

Before the last step, the chip will enter WAIT mode if CCM_CLPCR[1:0] is
set to 2'b01, or enter STOP mode if CCM_CLPCR[1:0] is set to 2'b10.

The patch implements a recommended workaround for this issue.

1. SW triggers irq #32(IOMUX) to be always pending manually by setting
   IOMUX_GPR1_GINT bit;
2. SW should then unmask it in GPC before setting CCM LPM;
3. SW should mask it right after CCM LPM is set (bit0-1 of CCM_CLPCR).

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
This commit is contained in:
Shawn Guo
2013-10-16 19:52:00 +08:00
parent 1d674a73c5
commit d48866fefd
3 changed files with 31 additions and 2 deletions
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3
arch/arm/mach-imx/common.h
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@@ -13,6 +13,7 @@
#include <linux/reboot.h>
struct irq_data;
struct platform_device;
struct pt_regs;
struct clk;
@@ -136,6 +137,8 @@ void imx_gpc_pre_suspend(void);
void imx_gpc_post_resume(void);
void imx_gpc_mask_all(void);
void imx_gpc_restore_all(void);
void imx_gpc_irq_mask(struct irq_data *d);
void imx_gpc_irq_unmask(struct irq_data *d);
void imx_anatop_init(void);
void imx_anatop_pre_suspend(void);
void imx_anatop_post_resume(void);