From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e7.ny.us.ibm.com (e7.ny.us.ibm.com [32.97.182.137]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 78AB41A0C76 for ; Wed, 14 Jan 2015 22:13:47 +1100 (AEDT) Received: from /spool/local by e7.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 14 Jan 2015 06:13:44 -0500 Received: from b01cxnp23033.gho.pok.ibm.com (b01cxnp23033.gho.pok.ibm.com [9.57.198.28]) by d01dlp02.pok.ibm.com (Postfix) with ESMTP id E000A6E8040 for ; Wed, 14 Jan 2015 06:05:34 -0500 (EST) Received: from d01av05.pok.ibm.com (d01av05.pok.ibm.com [9.56.224.195]) by b01cxnp23033.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id t0EBDf1f26017812 for ; Wed, 14 Jan 2015 11:13:41 GMT Received: from d01av05.pok.ibm.com (localhost [127.0.0.1]) by d01av05.pok.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id t0EBDfo9005424 for ; Wed, 14 Jan 2015 06:13:41 -0500 From: "Shreyas B. Prabhu" To: linux-kernel@vger.kernel.org Subject: [PATCH] powerpc: powernv: winkle: Restore LPCR with LPCR_PECE1 cleared Date: Wed, 14 Jan 2015 16:43:21 +0530 Message-Id: <1421234001-24886-1-git-send-email-shreyas@linux.vnet.ibm.com> Cc: "Shreyas B. Prabhu" , Paul Mackerras , linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , LPCR_PECE1 bit controls whether decrementer interrupts are allowed to cause exit from power-saving mode. While waking up from winkle, restoring LPCR with LPCR_PECE1 set (i.e Decrementer interrupts allowed) can cause issue in the following scenario: - All the threads in a core are offlined. The core enters deep winkle. - Spurious interrupt wakes up a thread in the core. Here LPCR is restored with LPCR_PECE1 bit set. - Since it was a spurious interrupt on a offline thread, the thread clears the interrupt and goes back to winkle. - Here before the thread executes winkle and puts the core into deep winkle, if a decrementer interrupt occurs on any of the sibling threads in the core that thread wakes up. - Since in offline loop we are flushing interrupt only in case of external interrupt, the decrementer interrupt does not get flushed. So at this stage the thread is stuck in this is loop of waking up at 0x100 due to decrementer interrupt, not flushing the interrupt as only external interrupts get flushed, entering winkle, waking up at 0x100 again. Fix this by programming PORE to restore LPCR with LPCR_PECE1 bit cleared when waking up from winkle. Signed-off-by: Shreyas B. Prabhu Cc: Michael Ellerman Cc: Paul Mackerras Cc: Benjamin Herrenschmidt Cc: linuxppc-dev@lists.ozlabs.org --- This issue is separate from the issue which Alexey has reported. Fix for that is still pending. arch/powerpc/platforms/powernv/setup.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c index ad0e32e..83067b1 100644 --- a/arch/powerpc/platforms/powernv/setup.c +++ b/arch/powerpc/platforms/powernv/setup.c @@ -298,7 +298,7 @@ int pnv_save_sprs_for_winkle(void) * all cpus at boot. Get these reg values of current cpu and use the * same accross all cpus. */ - uint64_t lpcr_val = mfspr(SPRN_LPCR); + uint64_t lpcr_val = mfspr(SPRN_LPCR) & ~(u64)LPCR_PECE1; uint64_t hid0_val = mfspr(SPRN_HID0); uint64_t hid1_val = mfspr(SPRN_HID1); uint64_t hid4_val = mfspr(SPRN_HID4); -- 1.9.3