From patchwork Tue Dec 8 17:37:37 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Geert Uytterhoeven X-Patchwork-Id: 7800361 Return-Path: X-Original-To: patchwork-ltsi-dev@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id EF8C59F349 for ; Tue, 8 Dec 2015 17:38:09 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id EBAC6204D2 for ; Tue, 8 Dec 2015 17:38:08 +0000 (UTC) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org [140.211.169.12]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E771F20452 for ; Tue, 8 Dec 2015 17:38:07 +0000 (UTC) Received: from mail.linux-foundation.org (localhost [127.0.0.1]) by mail.linuxfoundation.org (Postfix) with ESMTP id AA753CE7; Tue, 8 Dec 2015 17:38:03 +0000 (UTC) X-Original-To: ltsi-dev@lists.linuxfoundation.org Delivered-To: ltsi-dev@mail.linuxfoundation.org Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id C810ACD6 for ; Tue, 8 Dec 2015 17:38:02 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from xavier.telenet-ops.be (xavier.telenet-ops.be [195.130.132.52]) by smtp1.linuxfoundation.org (Postfix) with ESMTP id 19FF1184 for ; Tue, 8 Dec 2015 17:38:00 +0000 (UTC) Received: from ayla.of.borg ([84.195.106.123]) by xavier.telenet-ops.be with bizsmtp id r5dy1r0032fm56U015dymx; Tue, 08 Dec 2015 18:37:59 +0100 Received: from ramsan.of.borg ([192.168.97.29] helo=ramsan) by ayla.of.borg with esmtp (Exim 4.82) (envelope-from ) id 1a6MD8-0007bo-3z; Tue, 08 Dec 2015 18:37:58 +0100 Received: from geert by ramsan with local (Exim 4.82) (envelope-from ) id 1a6MDA-00084q-4T; Tue, 08 Dec 2015 18:38:00 +0100 From: Geert Uytterhoeven To: Greg Kroah-Hartman Date: Tue, 8 Dec 2015 18:37:37 +0100 Message-Id: <1449596261-31005-2-git-send-email-geert+renesas@glider.be> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1449596261-31005-1-git-send-email-geert+renesas@glider.be> References: <1449596261-31005-1-git-send-email-geert+renesas@glider.be> X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org Cc: ltsi-dev@lists.linuxfoundation.org, Geert Uytterhoeven , Peter Zijlstra , Daniel Lezcano , Magnus Damm , Thomas Gleixner , Ingo Molnar Subject: [LTSI-dev] [PATCH 1/5] clockevents/drivers/sh_cmt: Only perform clocksource suspend/resume if enabled X-BeenThere: ltsi-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: "A list to discuss patches, development, and other things related to the LTSI project" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: ltsi-dev-bounces@lists.linuxfoundation.org Errors-To: ltsi-dev-bounces@lists.linuxfoundation.org X-Virus-Scanned: ClamAV using ClamSMTP Currently the sh_cmt clocksource timer is disabled or enabled unconditionally on clocksource suspend resp. resume, even if a better clocksource is present (e.g. arch_sys_counter) and the sh_cmt clocksource is not enabled. As sh_cmt is a syscore device when its timer is enabled, this may lead to a genpd.prepared_count imbalance in the presence of PM Domains, which may cause a lock-up during reboot after s2ram. During suspend: - pm_genpd_prepare() is called for all non-syscore devices (incl. sh_cmt), increasing genpd.prepared_count for each device, - clocksource.suspend() is called for all clocksource devices, - sh_cmt_clocksource_suspend() calls sh_cmt_stop(), which is a no-op as the clocksource was not enabled. During resume: - clocksource.resume() is called for all clocksource devices, - sh_cmt_clocksource_resume() calls sh_cmt_start(), which enables the clocksource timer, and turns sh_cmt into a syscore device, - pm_genpd_complete() is called for all non-syscore devices (excl. sh_cmt now!), decreasing genpd.prepared_count for each device but sh_cmt. Now genpd.prepared_count of the PM Domain containing sh_cmt is still 1 instead of zero. On subsequent suspend/resume cycles, sh_cmt is still a syscore device, hence it's skipped for pm_genpd_{prepare,complete}(), keeping the imbalance of genpd.prepared_count at 1. During reboot: - platform_drv_shutdown() is called for any platform device that has a driver with a .shutdown() method (only rcar-dmac on R-Car Gen2), - platform_drv_shutdown() calls dev_pm_domain_detach(), which calls genpd_dev_pm_detach(), - genpd_dev_pm_detach() keeps calling pm_genpd_remove_device() until it doesn't return -EAGAIN[*], - If the device is part of the same PM Domain as sh_cmt, pm_genpd_remove_device() always fails with -EAGAIN due to genpd.prepared_count > 0. - Infinite loop in genpd_dev_pm_detach()[*]. [*] Commit 93af5e9354432828 ("PM / Domains: Avoid infinite loops in attach/detach code") already limited the number of loop iterations, avoiding the lock-up. To fix this, only disable or enable the clocksource timer on clocksource suspend resp. resume if the clocksource was enabled. This was tested on r8a7791/koelsch with the CPG Clock Domain: - using arch_sys_counter as the clocksource, which is the default, and which showed the problem, - using sh_cmt as a clocksource ("echo ffca0000.timer > \ /sys/devices/system/clocksource/clocksource0/current_clocksource"), which behaves the same as before. Signed-off-by: Geert Uytterhoeven Signed-off-by: Daniel Lezcano Acked-by: Laurent Pinchart Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1438875126-12596-2-git-send-email-daniel.lezcano@linaro.org Signed-off-by: Ingo Molnar (cherry picked from commit 54d46b7fbcbd00fe4b20a27208e5909facc714e3) Signed-off-by: Geert Uytterhoeven --- drivers/clocksource/sh_cmt.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/clocksource/sh_cmt.c b/drivers/clocksource/sh_cmt.c index 7e4cd3473c7204f2..e4138e2a88f56b4e 100644 --- a/drivers/clocksource/sh_cmt.c +++ b/drivers/clocksource/sh_cmt.c @@ -661,6 +661,9 @@ static void sh_cmt_clocksource_suspend(struct clocksource *cs) { struct sh_cmt_channel *ch = cs_to_sh_cmt(cs); + if (!ch->cs_enabled) + return; + sh_cmt_stop(ch, FLAG_CLOCKSOURCE); pm_genpd_syscore_poweroff(&ch->cmt->pdev->dev); } @@ -669,6 +672,9 @@ static void sh_cmt_clocksource_resume(struct clocksource *cs) { struct sh_cmt_channel *ch = cs_to_sh_cmt(cs); + if (!ch->cs_enabled) + return; + pm_genpd_syscore_poweron(&ch->cmt->pdev->dev); sh_cmt_start(ch, FLAG_CLOCKSOURCE); }