Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752780AbaFETWa (ORCPT ); Thu, 5 Jun 2014 15:22:30 -0400 Received: from mail-ve0-f171.google.com ([209.85.128.171]:56005 "EHLO mail-ve0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752720AbaFETW2 (ORCPT ); Thu, 5 Jun 2014 15:22:28 -0400 MIME-Version: 1.0 In-Reply-To: <5390C19A.9060201@gmail.com> References: <1401398496-4624-1-git-send-email-dianders@chromium.org> <1401467562-5585-1-git-send-email-dianders@chromium.org> <5390C19A.9060201@gmail.com> Date: Thu, 5 Jun 2014 12:22:27 -0700 X-Google-Sender-Auth: NSmh7wMz-ueMxDS2Xm1xTDxzGS4 Message-ID: Subject: Re: [PATCH v2] clk: exynos5420: Keep aclk66_peric enabled during boot From: Doug Anderson To: Tomasz Figa Cc: Tomasz Figa , Mike Turquette , Kukjin Kim , linux-samsung-soc , "linux-kernel@vger.kernel.org" , Olof Johansson , Javier Martinez Canillas , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Tomasz, On Thu, Jun 5, 2014 at 12:14 PM, Tomasz Figa wrote: > 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. OK, I'm happy to go back to v1 with the addition of the "return 0". Mike: are you OK with that? -- 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/