Commit 48c95841 authored by Anson Huang's avatar Anson Huang Committed by Shawn Guo
Browse files

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: default avatarAnson Huang <b20788@freescale.com>
Signed-off-by: default avatarShawn Guo <shawn.guo@linaro.org>
parent b4e844f0
Loading
Loading
Loading
Loading
+12 −4
Original line number Diff line number Diff line
@@ -156,10 +156,16 @@ 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);
	imx_gpc_irq_unmask(&iomuxc_irq_desc->irq_data);
@@ -219,6 +225,8 @@ void __init imx6q_pm_init(void)
	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.