Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755953Ab3J1VEk (ORCPT ); Mon, 28 Oct 2013 17:04:40 -0400 Received: from perceval.ideasonboard.com ([95.142.166.194]:58684 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751331Ab3J1VEi (ORCPT ); Mon, 28 Oct 2013 17:04:38 -0400 From: Laurent Pinchart To: linux-arm-kernel@lists.infradead.org Cc: Sylwester Nawrocki , linux@arm.linux.org.uk, mturquette@linaro.org, linux-mips@linux-mips.org, linux-sh@vger.kernel.org, jiada_wang@mentor.com, t.figa@samsung.com, linux-kernel@vger.kernel.org, kyungmin.park@samsung.com, myungjoo.ham@samsung.com, Sylwester Nawrocki , g.liakhovetski@gmx.de Subject: Re: [PATCH v6 0/5] clk: clock deregistration support Date: Mon, 28 Oct 2013 22:05:02 +0100 Message-ID: <13429728.zDYQ5qS5ur@avalon> User-Agent: KMail/4.10.5 (Linux/3.10.7-gentoo-r1; KDE/4.10.5; x86_64; ; ) In-Reply-To: <52420664.2040604@gmail.com> References: <1377874402-2944-1-git-send-email-s.nawrocki@samsung.com> <52420664.2040604@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4522 Lines: 127 Hi Sylwester, On Tuesday 24 September 2013 23:38:44 Sylwester Nawrocki wrote: > On 08/30/2013 04:53 PM, Sylwester Nawrocki wrote: > > This patch series implements clock deregistration in the common clock > > framework. Comparing to v5 it only includes further corrections of NULL > > clock handling. > > [...] > > > clk: Provide not locked variant of of_clk_get_from_provider() > > clkdev: Fix race condition in clock lookup from device tree > > clk: Add common __clk_get(), __clk_put() implementations > > clk: Assign module owner of a clock being registered > > clk: Implement clk_unregister > > Hi Mike, Russell, > > Would you have any further comments/suggestions on this series ? > > I have inspected all callers of clk_register() and all should be fine > with regards to dereferencing dev->driver. The first argument to this > function is either NULL or clk_register() is being called in drivers' > probe() callback, which ensures dev->driver won't change due to holding > dev->mutex. > > The only issue I found might be at the omap3isp driver, which provides > clock to its sub-drivers and takes reference on the sub-driver modules. > When sub-driver calls clk_get() all modules would get locked in memory, > due to circular reference. One solution to that could be to pass NULL > struct device pointer, as in the below patch. > > ---------8<------------------ > From ca5963041aad67e31324cb5d4d5e2cfce1706d4f Mon Sep 17 00:00:00 2001 > From: Sylwester Nawrocki > Date: Thu, 19 Sep 2013 23:52:04 +0200 > Subject: [PATCH] omap3isp: Pass NULL device pointer to clk_register() > > Signed-off-by: Sylwester Nawrocki > --- > drivers/media/platform/omap3isp/isp.c | 15 ++++++++++----- > drivers/media/platform/omap3isp/isp.h | 1 + > 2 files changed, 11 insertions(+), 5 deletions(-) > > diff --git a/drivers/media/platform/omap3isp/isp.c > b/drivers/media/platform/omap3isp/isp.c > index df3a0ec..d7f3c98 100644 > --- a/drivers/media/platform/omap3isp/isp.c > +++ b/drivers/media/platform/omap3isp/isp.c > @@ -290,9 +290,11 @@ static int isp_xclk_init(struct isp_device *isp) > struct clk_init_data init; > unsigned int i; > > + for (i = 0; i < ARRAY_SIZE(isp->xclks); ++i) > + isp->xclks[i] = ERR_PTR(-EINVAL); I don't think you've compile-tested this :-) > + > for (i = 0; i < ARRAY_SIZE(isp->xclks); ++i) { > struct isp_xclk *xclk = &isp->xclks[i]; > - struct clk *clk; > > xclk->isp = isp; > xclk->id = i == 0 ? ISP_XCLK_A : ISP_XCLK_B; > @@ -306,9 +308,9 @@ static int isp_xclk_init(struct isp_device *isp) > > xclk->hw.init = &init; > > - clk = devm_clk_register(isp->dev, &xclk->hw); > - if (IS_ERR(clk)) > - return PTR_ERR(clk); > + xclk->clk = clk_register(NULL, &xclk->hw); > + if (IS_ERR(xclk->clk)) > + return PTR_ERR(xclk->clk); This doesn't introduce any regression in the sense that it will trade a problem for another one, so I'm fine with it in the short. Could you add a small comment above the clk_register() call to explain why the first argument is NULL ? > > if (pdata->xclks[i].con_id == NULL && > pdata->xclks[i].dev_id == NULL) > @@ -320,7 +322,7 @@ static int isp_xclk_init(struct isp_device *isp) > > xclk->lookup->con_id = pdata->xclks[i].con_id; > xclk->lookup->dev_id = pdata->xclks[i].dev_id; > - xclk->lookup->clk = clk; > + xclk->lookup->clk = xclk->clk; > > clkdev_add(xclk->lookup); > } > @@ -335,6 +337,9 @@ static void isp_xclk_cleanup(struct isp_device *isp) > for (i = 0; i < ARRAY_SIZE(isp->xclks); ++i) { > struct isp_xclk *xclk = &isp->xclks[i]; > > + if (!IS_ERR(xclk->clk)) > + clk_unregister(xclk->clk); > + > if (xclk->lookup) > clkdev_drop(xclk->lookup); > } > diff --git a/drivers/media/platform/omap3isp/isp.h > b/drivers/media/platform/omap3isp/isp.h > index cd3eff4..1498f2b 100644 > --- a/drivers/media/platform/omap3isp/isp.h > +++ b/drivers/media/platform/omap3isp/isp.h > @@ -135,6 +135,7 @@ struct isp_xclk { > struct isp_device *isp; > struct clk_hw hw; > struct clk_lookup *lookup; > + struct clk *clk; > enum isp_xclk_id id; > > spinlock_t lock; /* Protects enabled and divider */ -- Regards, Laurent Pinchart -- 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/