From: "Shreyas B. Prabhu" <shreyas@linux.vnet.ibm.com> To: linux-kernel@vger.kernel.org Cc: "Shreyas B. Prabhu" <shreyas@linux.vnet.ibm.com>, Michael Ellerman <mpe@ellerman.id.au>, Paul Mackerras <paulus@samba.org>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, linuxppc-dev@lists.ozlabs.org Subject: [PATCH v2 2/2] powerpc: powernv: winkle: Restore LPCR with LPCR_PECE1 cleared Date: Mon, 19 Jan 2015 13:35:27 +0530 [thread overview] Message-ID: <1421654727-31656-2-git-send-email-shreyas@linux.vnet.ibm.com> (raw) In-Reply-To: <1421654727-31656-1-git-send-email-shreyas@linux.vnet.ibm.com> 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 <shreyas@linux.vnet.ibm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Paul Mackerras <paulus@samba.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: linuxppc-dev@lists.ozlabs.org --- Changes is v2: ============== Using the helper function introduced in the previous patch. 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..ded7fc8 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 = LPCR_CLEAR_PECE1(mfspr(SPRN_LPCR)); uint64_t hid0_val = mfspr(SPRN_HID0); uint64_t hid1_val = mfspr(SPRN_HID1); uint64_t hid4_val = mfspr(SPRN_HID4); -- 1.9.3
WARNING: multiple messages have this Message-ID (diff)
From: "Shreyas B. Prabhu" <shreyas@linux.vnet.ibm.com> To: linux-kernel@vger.kernel.org Cc: "Shreyas B. Prabhu" <shreyas@linux.vnet.ibm.com>, Paul Mackerras <paulus@samba.org>, linuxppc-dev@lists.ozlabs.org Subject: [PATCH v2 2/2] powerpc: powernv: winkle: Restore LPCR with LPCR_PECE1 cleared Date: Mon, 19 Jan 2015 13:35:27 +0530 [thread overview] Message-ID: <1421654727-31656-2-git-send-email-shreyas@linux.vnet.ibm.com> (raw) In-Reply-To: <1421654727-31656-1-git-send-email-shreyas@linux.vnet.ibm.com> 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 <shreyas@linux.vnet.ibm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Paul Mackerras <paulus@samba.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: linuxppc-dev@lists.ozlabs.org --- Changes is v2: ============== Using the helper function introduced in the previous patch. 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..ded7fc8 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 = LPCR_CLEAR_PECE1(mfspr(SPRN_LPCR)); uint64_t hid0_val = mfspr(SPRN_HID0); uint64_t hid1_val = mfspr(SPRN_HID1); uint64_t hid4_val = mfspr(SPRN_HID4); -- 1.9.3
next prev parent reply other threads:[~2015-01-19 8:05 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-01-19 8:05 [PATCH v2 1/2] powerpc: Add helpers for LPCR PECE1 operations Shreyas B. Prabhu 2015-01-19 8:05 ` Shreyas B. Prabhu 2015-01-19 8:05 ` Shreyas B. Prabhu [this message] 2015-01-19 8:05 ` [PATCH v2 2/2] powerpc: powernv: winkle: Restore LPCR with LPCR_PECE1 cleared Shreyas B. Prabhu 2015-01-23 3:06 ` [PATCH v2 1/2] powerpc: Add helpers for LPCR PECE1 operations Michael Ellerman 2015-01-23 3:06 ` Michael Ellerman 2015-01-23 3:46 ` Shreyas B Prabhu 2015-01-23 3:46 ` Shreyas B Prabhu 2015-01-23 4:20 ` Michael Ellerman 2015-01-23 4:20 ` Michael Ellerman
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