Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753257Ab1BPTgu (ORCPT ); Wed, 16 Feb 2011 14:36:50 -0500 Received: from smtp-out.google.com ([216.239.44.51]:38027 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752628Ab1BPTgs convert rfc822-to-8bit (ORCPT ); Wed, 16 Feb 2011 14:36:48 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=google.com; s=beta; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=EEZRR0g8nDH01GXRjyTrTduXdBV27TzCD4C4CNj8tuUxhQNkRPN2YKKr92ZVERd6ke 7SaBK6R56SMfTgxot15Q== MIME-Version: 1.0 In-Reply-To: <20110215170336.GP4152@n2100.arm.linux.org.uk> References: <1297724147-6320-1-git-send-email-ccross@android.com> <20110215170336.GP4152@n2100.arm.linux.org.uk> Date: Wed, 16 Feb 2011 11:36:45 -0800 X-Google-Sender-Auth: nsfljLdvzSgYVyrUO5iXFjy0JB0 Message-ID: Subject: Re: [PATCH v2] ARM: vfp: Always save VFP state in vfp_pm_suspend From: Colin Cross To: Russell King - ARM Linux Cc: linux-arm-kernel@lists.infradead.org, Catalin Marinas , linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2204 Lines: 54 On Tue, Feb 15, 2011 at 9:03 AM, Russell King - ARM Linux wrote: > On Mon, Feb 14, 2011 at 02:55:47PM -0800, Colin Cross wrote: >> diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c >> index 66bf8d1..7231d18 100644 >> --- a/arch/arm/vfp/vfpmodule.c >> +++ b/arch/arm/vfp/vfpmodule.c >> @@ -415,13 +415,13 @@ static int vfp_pm_suspend(struct sys_device *dev, pm_message_t state) >> ? ? ? struct thread_info *ti = current_thread_info(); >> ? ? ? u32 fpexc = fmrx(FPEXC); >> >> - ? ? /* if vfp is on, then save state for resumption */ >> - ? ? if (fpexc & FPEXC_EN) { >> + ? ? /* save state for resume */ >> + ? ? if (last_VFP_context[ti->cpu]) { > > I'm not entirely happy with this. > > It is true that last_VFP_context[] when non-NULL indicates who owns the > hardware VFP state, so saving it would seem logical. ?However, this new > code now saves the state with the saved fpexc indicating that it's disabled. > > This will cause a VFP exception to misbehave by reloading the state, and > then disabling the VFP unit. ?That will cause another VFP exception which > will find the VFP unit disabled, and re-enable it. ?All in all, this is > rather wasteful. > > So... > ? ? ? ?/* If lazy disable, re-enable the VFP ready for it to be saved */ > ? ? ? ?if (last_VFP_context[ti->cpu] != &ti->vfpstate) { > ? ? ? ? ? ? ? ?fpexc |= FPEXC_EN; > ? ? ? ? ? ? ? ?fmxr(FPEXC, fpexc); > ? ? ? ?} > ? ? ? ?/* If VFP is on, then save state for resumption */ > ? ? ? ?if (fpexc & FPEXC_EN) { > ? ? ? ? ? ? ? ?... I think v2 of the patch handles this case correctly: /* save state for resume */ if (last_VFP_context[ti->cpu]) { printk(KERN_DEBUG "%s: saving vfp state\n", __func__); fmxr(FPEXC, fpexc | FPEXC_EN); vfp_save_state(last_VFP_context[ti->cpu], fpexc); last_VFP_context[ti->cpu] = NULL; fmxr(FPEXC, fpexc & ~FPEXC_EN); } This version enables the VFP if it was not enabled, but saves the original fpexc value. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/