Hi Ohad, On 07/29/2014 05:57 AM, Ohad Ben-Cohen wrote: > Hi Suman, > > On Tue, Jul 8, 2014 at 7:22 PM, Suman Anna <s-anna@xxxxxx> wrote: >> The remoteproc driver core currently relies on iommu_present() on >> the bus the device is on, to perform MMU management. However, this >> logic doesn't scale for multi-arch, especially for processors that >> do not have an IOMMU. > > Is there a specific hw/scenario where you need this? Can you please > provide more details about it? We are trying to add a remoteproc driver for a small Cortex M3 called the WkupM3 used for suspend/resume management on TI AM335/AM437x SoCs. This processor does not have an MMU. Same is the case with another processor subsystem PRU-ICSS on AM335/AM437x. All these are platform devices, and the current iommu_present check will not scale for the same kernel image to support OMAP4/OMAP5 and AM335/AM437x. This patch mainly addresses the existing comments in the code, - * This works for simple cases, but will easily fail with - * platforms that do have an IOMMU, but not for this specific - * rproc. - * - * This will be easily solved by introducing hw capabilities - * that will be set by the remoteproc driver. > > Ideally we should add them to the commit log as well. > >> The individual platform implementations are required to set this >> flag appropriately. The default setting is to not have an MMU. > > Let's explicitly set the default please so this would be clear for > users reading the code. OK, I can update the existing drivers to explicitly set this field. > >> Cc: Sjur Brændeland <sjur.brandeland@xxxxxxxxxxxxxx> > > Sjur is no longer with STE, so no point in cc'ing his old email address. Yeah, I wasn't aware until I got a bounced email. > >> + /* >> + * All existing OMAP IPU and DSP processors do have an MMU, and >> + * are expected to use MMU, so this statement suffices. >> + * XXX: Replace this logic if and when a need arises. > > The last XXX comment is always true for any kernel code, so I'd drop it. Sure. regards Suman -- 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
