2010/1/29 Catalin Marinas <catalin.marinas@xxxxxxx>: > Hi Matthew, > > I've been trying for some time to use a rootfs (ext2) on a USB memory > stick on ARM platforms but without any success. The USB HCD driver is > ISP1760 which doesn't use DMA. > > ARM has a Harvard cache architecture and what I get is incoherency > between the I and D caches. The CPU I'm using (ARM11MPCore) has PIPT > caches with D-cache lines allocation on write. > > Basically, when user space tries to execute from a new page, it faults > and the data is requested via the VFS layer, SCSI block device and USB > mass storage from the ISP1760 driver. The page is then mapped into user > space and update_mmu_cache() called. > > However, since the driver is PIO, the data copied from the USB device > into RAM gets stuck in the D-cache. On the above page requesting path > there is no call to flush_dcache_page() to handle D-cache maintenance > (for DMA drivers, that's handled by the DMA API). > > Since the USB mass storage code has the information about the USB driver Sorry, I am a little confused that usb mass storage has what information about DMA or PIO of low level usb transfer? Thanks, -- Lei Ming -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
