From patchwork Fri Jul 24 17:54:25 2009 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Hilman X-Patchwork-Id: 37163 X-Patchwork-Delegate: khilman@deeprootsystems.com Received: from vger.kernel.org (vger.kernel.org [209.132.176.167]) by demeter.kernel.org (8.14.2/8.14.2) with ESMTP id n6OHsYSg005985 for ; Fri, 24 Jul 2009 17:54:36 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752349AbZGXRye (ORCPT ); Fri, 24 Jul 2009 13:54:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752834AbZGXRye (ORCPT ); Fri, 24 Jul 2009 13:54:34 -0400 Received: from mail-px0-f184.google.com ([209.85.216.184]:61046 "EHLO mail-px0-f184.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752349AbZGXRyd (ORCPT ); Fri, 24 Jul 2009 13:54:33 -0400 Received: by mail-px0-f184.google.com with SMTP id 14so494297pxi.33 for ; Fri, 24 Jul 2009 10:54:34 -0700 (PDT) Received: by 10.114.78.15 with SMTP id a15mr4718485wab.214.1248458073902; Fri, 24 Jul 2009 10:54:33 -0700 (PDT) Received: from localhost (deeprooted.net [216.254.16.51]) by mx.google.com with ESMTPS id d20sm7014866waa.47.2009.07.24.10.54.32 (version=TLSv1/SSLv3 cipher=RC4-MD5); Fri, 24 Jul 2009 10:54:33 -0700 (PDT) From: Kevin Hilman To: linux-omap@vger.kernel.org Cc: Jon Hunter Subject: [RFC/RFT 1/4] OMAP3: PM: Prevent hang in prcm_interrupt_handler Date: Fri, 24 Jul 2009 10:54:25 -0700 Message-Id: <1248458068-21747-2-git-send-email-khilman@deeprootsystems.com> X-Mailer: git-send-email 1.6.3.3 In-Reply-To: <1248458068-21747-1-git-send-email-khilman@deeprootsystems.com> References: <1248458068-21747-1-git-send-email-khilman@deeprootsystems.com> Sender: linux-omap-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-omap@vger.kernel.org From: Jon Hunter There are two scenarios where a race condition could result in a hang in the prcm_interrupt handler. These are: 1). Waiting for PRM_IRQSTATUS_MPU register to clear. Bit 0 of the PRM_IRQSTATUS_MPU register indicates that a wake-up event is pending for the MPU. This bit can only be cleared if the all the wake-up events latched in the various PM_WKST_x registers have been cleared. If a wake-up event occurred during the processing of the prcm interrupt handler, after the corresponding PM_WKST_x register was checked but before the PRM_IRQSTATUS_MPU was cleared, then the CPU would be stuck forever waiting for bit 0 in PRM_IRQSTATUS_MPU to be cleared. 2). Waiting for the PM_WKST_x register to clear. Some power domains have more than one wake-up source. The PM_WKST_x registers indicate the source of a wake-up event and need to be cleared after a wake-up event occurs. When the PM_WKST_x registers are read and before they are cleared, it is possible that another wake-up event could occur causing another bit to be set in one of the PM_WKST_x registers. If this did occur after reading a PM_WKST_x register then the CPU would miss this event and get stuck forever in a loop waiting for that PM_WKST_x register to clear. This patch address the above race conditions that would result in a hang. Signed-off-by: Jon Hunter Reviewed-by: Paul Walmsley --- arch/arm/mach-omap2/pm34xx.c | 143 ++++++++++++++++++------------------------ 1 files changed, 60 insertions(+), 83 deletions(-) diff --git a/arch/arm/mach-omap2/pm34xx.c b/arch/arm/mach-omap2/pm34xx.c index 14f10bc..f6cc71a 100644 --- a/arch/arm/mach-omap2/pm34xx.c +++ b/arch/arm/mach-omap2/pm34xx.c @@ -194,97 +194,74 @@ static void omap3_save_secure_ram_context(u32 target_mpu_state) } } -/* PRCM Interrupt Handler for wakeups */ -static irqreturn_t prcm_interrupt_handler (int irq, void *dev_id) +/* + * PRCM Interrupt Handler Helper Function + * + * The purpose of this function is to clear any wake-up events latched + * in the PRCM PM_WKST_x registers. It is possible that a wake-up event + * may occur whilst attempting to clear a PM_WKST_x register and thus + * set another bit in this register. A while loop is used to ensure + * that any peripheral wake-up events occurring while attempting to + * clear the PM_WKST_x are detected and cleared. + */ +static void prcm_clear_mod_irqs(s16 module, u8 regs) { - u32 wkst, irqstatus_mpu; - u32 fclk, iclk; - - /* WKUP */ - wkst = prm_read_mod_reg(WKUP_MOD, PM_WKST); - if (wkst) { - iclk = cm_read_mod_reg(WKUP_MOD, CM_ICLKEN); - fclk = cm_read_mod_reg(WKUP_MOD, CM_FCLKEN); - cm_set_mod_reg_bits(wkst, WKUP_MOD, CM_ICLKEN); - cm_set_mod_reg_bits(wkst, WKUP_MOD, CM_FCLKEN); - prm_write_mod_reg(wkst, WKUP_MOD, PM_WKST); - while (prm_read_mod_reg(WKUP_MOD, PM_WKST)) - cpu_relax(); - cm_write_mod_reg(iclk, WKUP_MOD, CM_ICLKEN); - cm_write_mod_reg(fclk, WKUP_MOD, CM_FCLKEN); - } + u32 wkst, fclk, iclk; + u16 wkst_off = (regs == 3) ? OMAP3430ES2_PM_WKST3 : PM_WKST1; + u16 fclk_off = (regs == 3) ? OMAP3430ES2_CM_FCLKEN3 : CM_FCLKEN1; + u16 iclk_off = (regs == 3) ? CM_ICLKEN3 : CM_ICLKEN1; - /* CORE */ - wkst = prm_read_mod_reg(CORE_MOD, PM_WKST1); - if (wkst) { - iclk = cm_read_mod_reg(CORE_MOD, CM_ICLKEN1); - fclk = cm_read_mod_reg(CORE_MOD, CM_FCLKEN1); - cm_set_mod_reg_bits(wkst, CORE_MOD, CM_ICLKEN1); - cm_set_mod_reg_bits(wkst, CORE_MOD, CM_FCLKEN1); - prm_write_mod_reg(wkst, CORE_MOD, PM_WKST1); - while (prm_read_mod_reg(CORE_MOD, PM_WKST1)) - cpu_relax(); - cm_write_mod_reg(iclk, CORE_MOD, CM_ICLKEN1); - cm_write_mod_reg(fclk, CORE_MOD, CM_FCLKEN1); - } - wkst = prm_read_mod_reg(CORE_MOD, OMAP3430ES2_PM_WKST3); + wkst = prm_read_mod_reg(module, wkst_off); if (wkst) { - iclk = cm_read_mod_reg(CORE_MOD, CM_ICLKEN3); - fclk = cm_read_mod_reg(CORE_MOD, OMAP3430ES2_CM_FCLKEN3); - cm_set_mod_reg_bits(wkst, CORE_MOD, CM_ICLKEN3); - cm_set_mod_reg_bits(wkst, CORE_MOD, OMAP3430ES2_CM_FCLKEN3); - prm_write_mod_reg(wkst, CORE_MOD, OMAP3430ES2_PM_WKST3); - while (prm_read_mod_reg(CORE_MOD, OMAP3430ES2_PM_WKST3)) - cpu_relax(); - cm_write_mod_reg(iclk, CORE_MOD, CM_ICLKEN3); - cm_write_mod_reg(fclk, CORE_MOD, OMAP3430ES2_CM_FCLKEN3); - } - - /* PER */ - wkst = prm_read_mod_reg(OMAP3430_PER_MOD, PM_WKST); - if (wkst) { - iclk = cm_read_mod_reg(OMAP3430_PER_MOD, CM_ICLKEN); - fclk = cm_read_mod_reg(OMAP3430_PER_MOD, CM_FCLKEN); - cm_set_mod_reg_bits(wkst, OMAP3430_PER_MOD, CM_ICLKEN); - cm_set_mod_reg_bits(wkst, OMAP3430_PER_MOD, CM_FCLKEN); - prm_write_mod_reg(wkst, OMAP3430_PER_MOD, PM_WKST); - while (prm_read_mod_reg(OMAP3430_PER_MOD, PM_WKST)) - cpu_relax(); - cm_write_mod_reg(iclk, OMAP3430_PER_MOD, CM_ICLKEN); - cm_write_mod_reg(fclk, OMAP3430_PER_MOD, CM_FCLKEN); + iclk = cm_read_mod_reg(module, iclk_off); + fclk = cm_read_mod_reg(module, fclk_off); + while (wkst) { + cm_set_mod_reg_bits(wkst, module, iclk_off); + cm_set_mod_reg_bits(wkst, module, fclk_off); + prm_write_mod_reg(wkst, module, wkst_off); + wkst = prm_read_mod_reg(module, wkst_off); + } + cm_write_mod_reg(iclk, module, iclk_off); + cm_write_mod_reg(fclk, module, fclk_off); } +} - if (omap_rev() > OMAP3430_REV_ES1_0) { - /* USBHOST */ - wkst = prm_read_mod_reg(OMAP3430ES2_USBHOST_MOD, PM_WKST); - if (wkst) { - iclk = cm_read_mod_reg(OMAP3430ES2_USBHOST_MOD, - CM_ICLKEN); - fclk = cm_read_mod_reg(OMAP3430ES2_USBHOST_MOD, - CM_FCLKEN); - cm_set_mod_reg_bits(wkst, OMAP3430ES2_USBHOST_MOD, - CM_ICLKEN); - cm_set_mod_reg_bits(wkst, OMAP3430ES2_USBHOST_MOD, - CM_FCLKEN); - prm_write_mod_reg(wkst, OMAP3430ES2_USBHOST_MOD, - PM_WKST); - while (prm_read_mod_reg(OMAP3430ES2_USBHOST_MOD, - PM_WKST)) - cpu_relax(); - cm_write_mod_reg(iclk, OMAP3430ES2_USBHOST_MOD, - CM_ICLKEN); - cm_write_mod_reg(fclk, OMAP3430ES2_USBHOST_MOD, - CM_FCLKEN); +/* + * PRCM Interrupt Handler + * + * The PRM_IRQSTATUS_MPU register indicates if there are any pending + * interrupts from the PRCM for the MPU. These bits must be cleared in + * order to clear the PRCM interrupt. The PRCM interrupt handler is + * implemented to simply clear the PRM_IRQSTATUS_MPU in order to clear + * the PRCM interrupt. Please note that bit 0 of the PRM_IRQSTATUS_MPU + * register indicates that a wake-up event is pending for the MPU and + * this bit can only be cleared if the all the wake-up events latched + * in the various PM_WKST_x registers have been cleared. The interrupt + * handler is implemented using a do-while loop so that if a wake-up + * event occurred during the processing of the prcm interrupt handler + * (setting a bit in the corresponding PM_WKST_x register and thus + * preventing us from clearing bit 0 of the PRM_IRQSTATUS_MPU register) + * this would be handled. + */ +static irqreturn_t prcm_interrupt_handler (int irq, void *dev_id) +{ + u32 irqstatus_mpu; + + do { + prcm_clear_mod_irqs(WKUP_MOD, 1); + prcm_clear_mod_irqs(CORE_MOD, 1); + prcm_clear_mod_irqs(OMAP3430_PER_MOD, 1); + if (omap_rev() > OMAP3430_REV_ES1_0) { + prcm_clear_mod_irqs(CORE_MOD, 3); + prcm_clear_mod_irqs(OMAP3430ES2_USBHOST_MOD, 1); } - } - irqstatus_mpu = prm_read_mod_reg(OCP_MOD, - OMAP3_PRM_IRQSTATUS_MPU_OFFSET); - prm_write_mod_reg(irqstatus_mpu, OCP_MOD, - OMAP3_PRM_IRQSTATUS_MPU_OFFSET); + irqstatus_mpu = prm_read_mod_reg(OCP_MOD, + OMAP3_PRM_IRQSTATUS_MPU_OFFSET); + prm_write_mod_reg(irqstatus_mpu, OCP_MOD, + OMAP3_PRM_IRQSTATUS_MPU_OFFSET); - while (prm_read_mod_reg(OCP_MOD, OMAP3_PRM_IRQSTATUS_MPU_OFFSET)) - cpu_relax(); + } while (prm_read_mod_reg(OCP_MOD, OMAP3_PRM_IRQSTATUS_MPU_OFFSET)); return IRQ_HANDLED; }