| Message ID | alpine.DEB.2.00.1108192131170.24016@utopia.booyaka.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
> From: Paul Walmsley<paul@pwsan.com> > 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 > <ohad@wizery.com>. I'm simply writing the commit message and passing > it along. > > ... > > Thanks to Luciano Coelho<coelho@ti.com> for reporting the problem. > Thanks to Ohad Ben-Cohen<ohad@wizery.com> for tracking the problem > down, generating a temporary workaround, and proposing a patch to deal > with the problem. Thanks to Rajendra Nayak<rnayak@ti.com> for > proposing another patch to deal with the problem. Thanks to Felipe > Balbi<balbi@ti.com> for comments. > > 1. Coelho, Luciano<coelho@ti.com>. _Re: Oops on ehci_hcd when > booting 3.0.0-rc2 on panda_. Tue, 09 Aug 2011 14:26:08 +0300. > Posted to the<linux-omap@vger.kernel.org> mailing list. Available > from (among others) > http://www.spinics.net/linux/lists/linux-omap/msg55213.html > > 2. Munegowda, Keshava<keshava_mgowda@ti.com>. _Re: Oops on ehci_hcd > when booting 3.0.0-rc2 on panda_. Thu, 11 Aug 2011 13:51:05 +0530. > Posted to the<linux-omap@vger.kernel.org> mailing list. Available > from (among others) > http://www.spinics.net/linux/lists/linux-omap/msg55371.html > > 3. King, Russell<linux@arm.linux.org.uk>. _Re: [PATCH 5/8] OMAP4: > PM: TEMP: Prevent l3init from idling/force sleep_. Thu, 23 Jun > 2011 16:22:49 +0100. Posted to the<linux-omap@vger.kernel.org> > mailing list. Available from (among others) > http://www.mail-archive.com/linux-omap@vger.kernel.org/msg51392.html > > Signed-off-by: Paul Walmsley<paul@pwsan.com> > Cc: Luciano Coelho<coelho@ti.com> > Cc: Ohad Ben-Cohen<ohad@wizery.com> > Cc: Rajendra Nayak<rnayak@ti.com> > Cc: Benoît Cousson<b-cousson@ti.com> > --- Thanks for the change log. Here is my ack if you need one. Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com> Regards santosh
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++)