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91 lines
3.8 KiB
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From: Catalin Marinas <catalin.marinas@arm.com>
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Subject: Re: [PATCH] ARM: vfp: Always save VFP state in vfp_pm_suspend
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Date: Mon, 14 Feb 2011 11:42:22 +0000
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Organization: ARM Limited
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Lines: 43
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Message-ID: <1297683742.30092.11.camel@e102109-lin.cambridge.arm.com>
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References: <1297638813-1315-1-git-send-email-ccross@android.com>
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Content-Type: text/plain; charset=UTF-8
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Cc: linux-arm-kernel@lists.infradead.org,
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Russell King <linux@arm.linux.org.uk>,
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linux-kernel@vger.kernel.org
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To: Colin Cross <ccross@android.com>
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X-From: linux-kernel-owner@vger.kernel.org Mon Feb 14 12:42:45 2011
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Mon, 14 Feb 2011 11:42:28 +0000
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In-Reply-To: <1297638813-1315-1-git-send-email-ccross@android.com>
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Archived-At: <http://permalink.gmane.org/gmane.linux.kernel/1099685>
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On Sun, 2011-02-13 at 23:13 +0000, Colin Cross wrote:
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> vfp_pm_suspend should save the VFP state any time there is
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> a last_VFP_context. If it only saves when the VFP is enabled,
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> the state can get lost when, on a UP system:
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> Thread 1 uses the VFP
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> Context switch occurs to thread 2, VFP is disabled but the
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> VFP context is not saved to allow lazy save and restore
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> Thread 2 initiates suspend
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> vfp_pm_suspend is called with the VFP disabled, but the
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> context has not been saved.
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At this point is it guaranteed that the thread won't migrate to another
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CPU? If not, we should use get/put_cpu.
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> --- a/arch/arm/vfp/vfpmodule.c
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> +++ b/arch/arm/vfp/vfpmodule.c
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> @@ -415,13 +415,12 @@ static int vfp_pm_suspend(struct sys_device *dev, pm_message_t state)
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> struct thread_info *ti = current_thread_info();
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> u32 fpexc = fmrx(FPEXC);
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>
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> - /* if vfp is on, then save state for resumption */
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> - if (fpexc & FPEXC_EN) {
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> + /* save state for resume */
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> + if (last_VFP_context[ti->cpu]) {
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> printk(KERN_DEBUG "%s: saving vfp state\n", __func__);
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> - vfp_save_state(&ti->vfpstate, fpexc);
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> -
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> - /* disable, just in case */
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> - fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
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> + fmxr(FPEXC, fpexc | FPEXC_EN);
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> + vfp_save_state(last_VFP_context[ti->cpu], fpexc);
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> + fmxr(FPEXC, fpexc & ~FPEXC_EN);
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> }
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We may want to set the last_VFP_context to NULL so that after resuming
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(to the same thread) we force the VFP reload from the vfpstate
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structure. The vfp_support_entry code ignores the reloading if the
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last_VFP_context is the same as vfpstate.
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--
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Catalin
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