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Date: Tue, 24 Dec 2013 17:19:21 -0500 From: Anson Huang <b20788@...escale.com> To: <shawn.guo@...aro.org>, <kernel@...gutronix.de> CC: <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org> Subject: [PATCH V2] 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@...escale.com> --- 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 --- a/arch/arm/mach-imx/pm-imx6q.c +++ b/arch/arm/mach-imx/pm-imx6q.c @@ -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); imx_gpc_irq_unmask(&iomuxc_irq_desc->irq_data); @@ -219,6 +222,8 @@ 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. -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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