From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from caramon.arm.linux.org.uk ([78.32.30.218]:45348 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760668Ab0HFI76 (ORCPT ); Fri, 6 Aug 2010 04:59:58 -0400 Date: Fri, 6 Aug 2010 09:59:41 +0100 From: Russell King - ARM Linux Subject: Re: [PATCH] arm: msm: Add MSM IOMMU support. Message-ID: <20100806085941.GA15852@n2100.arm.linux.org.uk> References: <1281062204-21880-1-git-send-email-stepanm@codeaurora.org> <20100806073333.GA14965@n2100.arm.linux.org.uk> <93bd044b61aed19a3571bc019af0252a.squirrel@www.codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <93bd044b61aed19a3571bc019af0252a.squirrel@www.codeaurora.org> Sender: linux-arm-msm-owner@vger.kernel.org List-ID: To: stepanm@codeaurora.org Cc: dwalker@codeaurora.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org On Fri, Aug 06, 2010 at 01:17:46AM -0700, stepanm@codeaurora.org wrote: > Thank you for your comments. I will apply the fixes you have mentioned. I > am flushing the cache when I update the page table because the page table > lives in regular RAM that is mapped as cacheable on the CPU side, and in > the default configuration the IOMMU reads the page table from RAM. That's fine, but use the right function. > So, I > have put in the flush call to give the IOMMU a coherent view of the page > tables. I realize it is more efficient to just flush that specific part of > L2, but this is just the basic version of the driver and that optimization > will be eventually put in. Here, you're talking about L2 again, but your code only touches the L1 cache. I think you're confused about caching. > What did you mean by: > > Any reason you can't have some kind of struct device instead? > > Are you referring to the clock line? As far as I understand it, the kernel > tracks the clocks by a string name, but I can look into it further. No. /** * clk_get - lookup and obtain a reference to a clock producer. * @dev: device for clock "consumer" * @id: clock comsumer ID * * Returns a struct clk corresponding to the clock producer, or * valid IS_ERR() condition containing errno. The implementation * uses @dev and @id to determine the clock consumer, and thereby * the clock producer. (IOW, @id may be identical strings, but * clk_get may return different clock producers depending on @dev.) The intention is that 'id' is specific to each 'dev', and identifies the connection on 'dev' that you want the clock for. It's the _consumer's_ name, nothing to do with the clock producer. There's also clk_get_sys() if you don't have a struct device.