Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752328AbaFETOw (ORCPT ); Thu, 5 Jun 2014 15:14:52 -0400 Received: from mail-wi0-f179.google.com ([209.85.212.179]:38530 "EHLO mail-wi0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751434AbaFETOv (ORCPT ); Thu, 5 Jun 2014 15:14:51 -0400 Message-ID: <5390C19A.9060201@gmail.com> Date: Thu, 05 Jun 2014 21:14:34 +0200 From: Tomasz Figa User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: Doug Anderson , Tomasz Figa , Mike Turquette , Kukjin Kim CC: linux-samsung-soc , "linux-kernel@vger.kernel.org" , Olof Johansson , Javier Martinez Canillas , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH v2] clk: exynos5420: Keep aclk66_peric enabled during boot References: <1401398496-4624-1-git-send-email-dianders@chromium.org> <1401467562-5585-1-git-send-email-dianders@chromium.org> In-Reply-To: X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05.06.2014 20:48, Doug Anderson wrote: > Tomasz / Mike, > > On Fri, May 30, 2014 at 9:32 AM, Doug Anderson wrote: >> Right now if you've got earlyprintk enabled on exynos5420-peach-pit >> then you'll get a hang on boot. Here's why: >> >> 1. The i2c-s3c2410 driver will probe at subsys_initcall. It will >> enable its clock and disable it. This is the clock "i2c2". >> 2. The act of disabling "i2c2" will disable its parents. In this case >> the parent is "aclk66_peric". There are no other children of >> "aclk66_peric" officially enabled, so "aclk66_peric" will be turned >> off (despite being CLK_IGNORE_UNUSED, but that's by design). >> 3. The next time you try to earlyprintk you'll do so without the UART >> clock enabled. That's because the UART clocks are also children of >> "aclk66_peric". You'll hang. >> >> There's no good place to put a clock enable for earlyprintk, which is >> handled by a bunch of assembly code. The best we can do is to handle >> this in the clock driver. >> >> Signed-off-by: Doug Anderson >> Tested-by: Javier Martinez Canillas >> --- >> Changes in v2: >> - Use GATE_A and clk_get(). Save the clock for putting later. >> - Return 0 from exynos5420_clk_late_init(). >> >> drivers/clk/samsung/clk-exynos5420.c | 33 +++++++++++++++++++++++++++++++-- >> 1 file changed, 31 insertions(+), 2 deletions(-) > > Are there other changes you'd like me to make to this? It would be > really nice to get this in for 3.16 so the system doesn't just > mysteriously hang when you use earlyprintk. We can probably take this as an -rc fix, so it should be fine. However I still don't see the point of exporting this clock and polluting the global clkdev namespace. Even the diffstat looks better in v1. Best regards, Tomasz -- 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/