From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Mike Frysinger" Subject: Re: [PATCH 01/16] Blackfin SPI Driver: ensure cache coherency before doing DMA Date: Thu, 20 Nov 2008 15:58:13 -0500 Message-ID: <8bd0f97a0811201258j14dfcf46vce1655632bb12e2@mail.gmail.com> References: <1226994760-4301-1-git-send-email-cooloney@kernel.org> <1226994760-4301-2-git-send-email-cooloney@kernel.org> <200811201224.15493.david-b@pacbell.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, Vitja Makarov , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: "David Brownell" Return-path: In-Reply-To: <200811201224.15493.david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org> Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: spi-devel-general-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: linux-spi.vger.kernel.org On Thu, Nov 20, 2008 at 15:24, David Brownell wrote: > On Monday 17 November 2008, Bryan Wu wrote: >> /* set transfer mode, and enable SPI */ >> dev_dbg(&drv_data->pdev->dev, "doing DMA in.\n"); >> >> + /* invalidate caches, if needed */ >> + if (bfin_addr_dcachable((unsigned long) drv_data->rx)) >> + invalidate_dcache_range((unsigned long) drv_data->rx, >> + (unsigned long) (drv_data->rx + >> + drv_data->len)); > > Could you explain why you're not using dma_map_*() calls > or the rx_dma (and tx_dma) addresses the caller may pass? i'm not familiar with said API. i worked with what was there already. > As a rule, you should use the standard kernel interfaces > for such stuff instead of platform-specific calls like > those two. There are a LOT more developers who can find > and fix bugs that way. could you elaborate on the common calls that would replace these ? > Also, this patch affects the "not full duplex" branch of > this routine. DMA here seems unusually convoluted ... but > if you didn't invalidate the cache (RX path) before > flushing it (TX path) and instead did it the other way > aroound, would you actually *need* separate branches? it's convoluted because the hardware sucks. it cant do full duplex with DMA. full duplex only works in the non-DMA case. -mike ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/