On Tue, Mar 8, 2011 at 3:55 AM, David Cohen <dacohen@xxxxxxxxx> wrote: > Hi Fernando, > > On Tue, Mar 8, 2011 at 11:13 AM, Sakari Ailus > <sakari.ailus@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote: >> Guzman Lugo, Fernando wrote: >>> On Mon, Mar 7, 2011 at 1:19 PM, David Cohen <dacohen@xxxxxxxxx> wrote: >>>> On Mon, Mar 7, 2011 at 9:17 PM, Guzman Lugo, Fernando >>>> <fernando.lugo@xxxxxx> wrote: >>>>> On Mon, Mar 7, 2011 at 7:10 AM, Michael Jones >>>>> <michael.jones@xxxxxxxxxxxxxxxx> 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. >> >> I think the driver for IPU (what is it, btw.?) must map the NULL address >> explicitly. It cannot rely on automatic allocation of the NULL address >> by the iommu even if it was the first allocation. > > That's an interesting question. My first thought was "it's not > automatic allocation", because it seems you know the specific 'da' IPU > needs. But then, looking into the driver's API, the automatic > allocation is defined whether the argument da == 0 (automatic > allocation) or da != 0 (fixed da). So, by default, the IOMMU driver > does not see da == 0 as valid address for fixed da. Then, why only > automatic allocation should use such address? My second point is: if > you're using automatic allocation, you *cannot* rely on specific da to > be used, as it would be up to IOMMU driver to choose. So, doesn't > matter the option, your driver seems to be wrong, unless I'm missing > something. If you were using fixed da passing da = 0, you were just > being lucky that it was the first request and automatic allocation > returned da == 0. yes, the driver is wrong, it should use only flag IOVMF_DA_ANON to get an automatic address. it has to be changed too. Regards, Fernando. > IMO either first page is not allowed at all or OMAP's IOMMU API should > change the way it checks if it's fixed da or not. > > Kind regards, > > David > >> >> -- >> Sakari Ailus >> sakari.ailus@xxxxxxxxxxxxxxxxxxxxxxxxxx >> > -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
