Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759390Ab3EWOrD (ORCPT ); Thu, 23 May 2013 10:47:03 -0400 Received: from comal.ext.ti.com ([198.47.26.152]:45353 "EHLO comal.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758360Ab3EWOrB (ORCPT ); Thu, 23 May 2013 10:47:01 -0400 Message-ID: <519E2BD4.9020906@ti.com> Date: Thu, 23 May 2013 17:46:44 +0300 From: Roger Quadros User-Agent: Mozilla/5.0 (X11; Linux i686; rv:16.0) Gecko/20121011 Thunderbird/16.0.1 MIME-Version: 1.0 To: Alan Stern CC: , , , , , Subject: Re: [PATCH 1/1] USB: ehci-omap: Reset dma_mask pointer on probe References: In-Reply-To: Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1796 Lines: 46 On 05/23/2013 05:11 PM, Alan Stern wrote: > On Thu, 23 May 2013, Roger Quadros wrote: > >> Device tree probed devices don't get dma_mask set. Previously >> we were setting the dma_mask pointer only if it was NULL. >> However, the address of 'omap_ehci_dma_mask' would change >> each time the module is unloaded and loaded back thus causing >> the devices dma_mask pointer to be invalid on the next load. >> >> This will cause page faults if any driver tries to access the >> old dma_mask pointer. >> >> Unconditionally re-setting the dma_mask pointer fixes this problem. > >> diff --git a/drivers/usb/host/ehci-omap.c b/drivers/usb/host/ehci-omap.c >> index 3d1491b..b33e306 100644 >> --- a/drivers/usb/host/ehci-omap.c >> +++ b/drivers/usb/host/ehci-omap.c >> @@ -146,8 +146,7 @@ static int ehci_hcd_omap_probe(struct platform_device *pdev) >> * Since shared usb code relies on it, set it here for now. >> * Once we have dma capability bindings this can go away. >> */ >> - if (!pdev->dev.dma_mask) >> - pdev->dev.dma_mask = &omap_ehci_dma_mask; >> + pdev->dev.dma_mask = &omap_ehci_dma_mask; > > Is this the solution that people have agreed on? There has been a lot > of discussion on this topic. In particular, there has been talk about > fixing it in the DT core. Fixing it in DT core would be best. > > This particular approach doesn't seem very robust. What if > pdev->dev.dma_mask is already set to a different value for some good > reason? > Then it breaks. But for OMAP, that situation seems unlikely. cheers, -roger -- 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/