From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Petazzoni Subject: Re: [PATCH v3 2/7] mmc: atmel-mci: prepare clk before calling enable Date: Tue, 16 Jul 2013 17:13:24 +0200 Message-ID: <20130716171324.7d483ada@skate> References: <1373986995-23899-1-git-send-email-b.brezillon@overkiz.com> <1373987208-24120-1-git-send-email-b.brezillon@overkiz.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: Received: from mail.free-electrons.com ([94.23.35.102]:36488 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932469Ab3GPPN3 (ORCPT ); Tue, 16 Jul 2013 11:13:29 -0400 In-Reply-To: <1373987208-24120-1-git-send-email-b.brezillon@overkiz.com> Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: Boris BREZILLON Cc: Nicolas Ferre , Ludovic Desroches , Jean-Christophe Plagniol-Villard , Chris Ball , linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Dear Boris BREZILLON, On Tue, 16 Jul 2013 17:06:48 +0200, Boris BREZILLON wrote: > buf = kmalloc(ATMCI_REGS_SIZE, GFP_KERNEL); > if (!buf) > @@ -389,9 +391,13 @@ static int atmci_regs_show(struct seq_file *s, void *v) > * consistent. > */ > spin_lock_bh(&host->lock); > - clk_enable(host->mck); > + ret = clk_prepare_enable(host->mck); I am not very familiar with the spin_lock_bh() variant, but are you sure we are allowed to sleep within a spin_lock_bh()-protected critical section? Remember that clk_prepare_enable() calls both ->prepare() and ->enable() for the clock, and ->prepare() is allowed to sleep, while ->enable() is guaranteed not to sleep. Therefore, clk_prepare() is usually called at probe time, while clk_enable() is called whenever enabling/disabling the clock is really needed. So not all clk_enable() can transparently be converted into a clk_prepare_enable(). Best regards, Thomas -- Thomas Petazzoni, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com