From: ext David Cohen <dacohen@xxxxxxxxx> Subject: Re: [PATCH] omap: iommu: disallow mapping NULL address Date: Mon, 7 Mar 2011 23:35:31 +0200 > On Mon, Mar 7, 2011 at 11:19 PM, Laurent Pinchart > <laurent.pinchart@xxxxxxxxxxxxxxxx> wrote: >> Hi David, > > Hi Laurent, > >> >> On Monday 07 March 2011 20:41:21 David Cohen wrote: >>> On Mon, Mar 7, 2011 at 9:25 PM, Guzman Lugo, Fernando wrote: >>> > On Mon, Mar 7, 2011 at 1:19 PM, David Cohen wrote: >>> >> On Mon, Mar 7, 2011 at 9:17 PM, Guzman Lugo, Fernando wrote: >>> >>> On Mon, Mar 7, 2011 at 7:10 AM, Michael Jones wrote: >>> >>>> From e7dbe4c4b64eb114f9b0804d6af3a3ca0e78acc8 Mon Sep 17 00:00:00 2001 >>> >>>> From: Michael Jones <michael.jones@xxxxxxxxxxxxxxxx> >>> >>>> Date: Mon, 7 Mar 2011 13:36:15 +0100 >>> >>>> Subject: [PATCH] omap: iommu: disallow mapping NULL address >>> >>>> >>> >>>> commit c7f4ab26e3bcdaeb3e19ec658e3ad9092f1a6ceb allowed mapping >>> >>>> the NULL address if da_start==0. Force da_start to exclude the >>> >>>> first page. >>> >>> >>> >>> what about devices that uses page 0? ipu after reset always starts >>> >>> from 0x00000000 how could we map that address?? >>> >> >>> >> from 0x0? The driver sees da == 0 as error. May I ask you why do you >>> >> want it? >>> > >>> > unlike DSP that you can load a register with the addres the DSP will >>> > boot, IPU core always starts from address 0x00000000, so if you take >>> > IPU out of reset it will try to access address 0x0 if not map it, >>> > there will be a mmu fault. >>> >>> Hm. Looks like the iommu should not restrict any da. The valid da >>> range should rely only on pdata. >>> Michael, what about just update ISP's da_start on omap-iommu.c file? >>> Set it to 0x1000. >> >> What about patching the OMAP3 ISP driver to use a non-zero value (maybe -1) as >> an invalid/freed pointer ? > > I wouldn't be comfortable to use 0 (or NULL) value as valid address on > ISP driver. The 'da' range (da_start and da_end) is defined per VM and > specified as platform data. IMO, to set da_start = 0x1000 seems to be > a correct approach for ISP as it's the only client for its IOMMU > instance. Sounds reasonable to me too. Considering 'da == 0' as invalid can be reasonably acceptable intuitively in most cases, and just let it allowed theoretically. -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
