From patchwork Sat Aug 20 03:32:12 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Paul Walmsley X-Patchwork-Id: 1082292 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by demeter2.kernel.org (8.14.4/8.14.4) with ESMTP id p7K3X6QY008545 for ; Sat, 20 Aug 2011 03:33:06 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754846Ab1HTDcO (ORCPT ); Fri, 19 Aug 2011 23:32:14 -0400 Received: from utopia.booyaka.com ([72.9.107.138]:57965 "EHLO utopia.booyaka.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754635Ab1HTDcN (ORCPT ); Fri, 19 Aug 2011 23:32:13 -0400 Received: (qmail 25627 invoked by uid 1019); 20 Aug 2011 03:32:13 -0000 Date: Fri, 19 Aug 2011 21:32:12 -0600 (MDT) From: Paul Walmsley To: Felipe Balbi cc: linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org, "Munegowda, Keshava" , Luciano Coelho , Rajendra Nayak , Ohad Ben-Cohen , "Cousson, Benoit" , sameo@linux.intel.com, linux-usb@vger.kernel.org, Kevin Hilman Subject: Re: [PATCH] OMAP4: clock: re-enable previous clockdomain enable/disable sequence (was Re: Oops on ehci_hcd when booting 3.0.0-rc2 on panda) In-Reply-To: <20110819230805.GA13317@legolas.emea.dhcp.ti.com> Message-ID: References: <1307356643.23002.413.camel@cumari> <20110606104417.GP18731@legolas.emea.dhcp.ti.com> <20110606110218.GS18731@legolas.emea.dhcp.ti.com> <1307358348.23002.419.camel@cumari> <1312889168.2407.148.camel@cumari> <4E43C41E.1080808@ti.com> <1313065224.2407.857.camel@cumari> <20110819230805.GA13317@legolas.emea.dhcp.ti.com> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Sender: linux-omap-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-omap@vger.kernel.org X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by milter-greylist-4.2.6 (demeter2.kernel.org [140.211.167.43]); Sat, 20 Aug 2011 03:33:06 +0000 (UTC) On Sat, 20 Aug 2011, Felipe Balbi wrote: > maybe add a comment here stating why this line is commented out ? > > > - omap2_clk_disable_clkdm_control(); > > + /* omap2_clk_disable_clkdm_control(); */ Thanks for your comments. I've updated the patch; it follows below. - Paul From: Paul Walmsley Date: Fri, 19 Aug 2011 16:59:56 -0600 Subject: [PATCH] OMAP4: clock: re-enable previous clockdomain enable/disable sequence MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit After commit 665d001338b494d6d62810aa99b4c0fa1a0884b9 ("OMAP2+: hwmod: Follow the recommended PRCM module enable sequence"), device drivers for OMAP IP blocks that do not use runtime PM can cause oopses or kernel instability[1][2]. This is because those non-runtime PM drivers do not use the hwmod code, which implements the correct IP block enable and disable sequence. Several options for dealing with this problem have been proposed: 1. Add a new field to the OMAP struct clk to mark clocks that are currently used by non-runtime PM drivers. Modify the clock code to use the old clockdomain sequence for these marked clocks. As drivers are converted to use runtime PM, remove the annotation from the clocks. 2. Similar to #1, but associate the flag with the struct omap_clk instead. 3. Add IDLEST wait support to the OMAP4 clock code, similar to the way it is implemented for OMAP2/3, and enable it in each struct clk currently used by non-runtime PM drivers. As drivers are converted to use runtime PM, remove the annotation from the clocks. 4. Do nothing; leave the problem to those responsible for the unconverted drivers. 5. Re-enable clock-based clockdomain control in the OMAP4 clock code. This would revert back to the behavior of Linux 3.0, simply with a slightly longer module enable/disable latency. Unfortunately, no approach seemed particularly good. Options 1 through 3 seemed unwise due to the following reasons: A. The OMAP struct clks are intended primarily to describe hardware clock nodes, and the intention is that no driver-specific data should be stored there (applies to #1) B. The resulting patch would have been quite large for the -rc series (applies to #1, #2, #3) C. The patch would have been a new, yet temporary hack; and similar fixes have drawn negative comments in the recent past (see for example [3]) Option 4 is undesirable because commit 665d001338b494d6d62810aa99b4c0fa1a0884b9 ("OMAP2+: hwmod: Follow the recommended PRCM module enable sequence") has resulted in a less stable kernel; and kernel stability is more important than OMAP4 power management. Option 5 is the approach taken in this patch. This seemed to be the least intrusive approach for 3.1-rc. The approach in this patch was originally proposed by Ohad Ben-Cohen . I'm simply writing the commit message and passing it along. ... Thanks to Luciano Coelho for reporting the problem. Thanks to Ohad Ben-Cohen for tracking the problem down, generating a temporary workaround, and proposing a patch to deal with the problem. Thanks to Rajendra Nayak for proposing another patch to deal with the problem. Thanks to Felipe Balbi for comments. 1. Coelho, Luciano . _Re: Oops on ehci_hcd when booting 3.0.0-rc2 on panda_. Tue, 09 Aug 2011 14:26:08 +0300. Posted to the mailing list. Available from (among others) http://www.spinics.net/linux/lists/linux-omap/msg55213.html 2. Munegowda, Keshava . _Re: Oops on ehci_hcd when booting 3.0.0-rc2 on panda_. Thu, 11 Aug 2011 13:51:05 +0530. Posted to the mailing list. Available from (among others) http://www.spinics.net/linux/lists/linux-omap/msg55371.html 3. King, Russell . _Re: [PATCH 5/8] OMAP4: PM: TEMP: Prevent l3init from idling/force sleep_. Thu, 23 Jun 2011 16:22:49 +0100. Posted to the mailing list. Available from (among others) http://www.mail-archive.com/linux-omap@vger.kernel.org/msg51392.html Signed-off-by: Paul Walmsley Cc: Luciano Coelho Cc: Ohad Ben-Cohen Cc: Rajendra Nayak Cc: Benoît Cousson Acked-by: Santosh Shilimkar --- arch/arm/mach-omap2/clock44xx_data.c | 8 +++++++- 1 files changed, 7 insertions(+), 1 deletions(-) diff --git a/arch/arm/mach-omap2/clock44xx_data.c b/arch/arm/mach-omap2/clock44xx_data.c index 2af0e3f..a3a1827 100644 --- a/arch/arm/mach-omap2/clock44xx_data.c +++ b/arch/arm/mach-omap2/clock44xx_data.c @@ -3379,7 +3379,13 @@ int __init omap4xxx_clk_init(void) } clk_init(&omap2_clk_functions); - omap2_clk_disable_clkdm_control(); + + /* + * Must stay commented until all OMAP SoC drivers are + * converted to runtime PM, or drivers may start crashing + * + * omap2_clk_disable_clkdm_control(); + */ for (c = omap44xx_clks; c < omap44xx_clks + ARRAY_SIZE(omap44xx_clks); c++)