On Tue, 2010-02-02 at 09:11 +0000, Sebastian Andrzej Siewior wrote: > * Catalin Marinas | 2010-02-01 17:29:14 [+0000]: > >> So, let's put this in the HCD drivers and be done with it. > > That is the correct place. MMC -hcd drivers for instance are doing this > way. > > >The patch below is what fixes the I-D cache incoherency issues on ARM. I > >don't particularly like the solution but it seems to be the only one > >available. > > The PIO-MMC drivers walk through a scatter list via sg_miter_start() and > friends. Those helpers take care of this automaticly. > > >IMHO, Linux should have functions similar to the DMA API but for PIO > >drivers (e.g. pio_map_single/pio_unmap_single) that non-coherent > >architectures can define, otherwise being no-ops. Any thoughts? > > What is wrong with flush_dcache_page() ? In this particular case, it's too many lines to do the virt_to_page for the transfer buffer since the HCD driver doesn't have access to the individual pages (via something like urb->sg). A better solution would be to move such loop in a flush_dcache_range() function to make it easier for drivers. Apart from that, flush_dcache_page() doesn't have any data flow information. Optimisations could be done on ARM if we know that the kernel only intends to read from a page (no flushing necessary with a non-aliasing D-cache). > And I think linux-arch is the appropriate place. For changes to the cache flushing API, yes, that's the right place. I'll get there with a patch. > > >diff --git a/drivers/usb/host/isp1760-hcd.c b/drivers/usb/host/isp1760-hcd.c > >index 27b8f7c..4d3eeee 100644 > >--- a/drivers/usb/host/isp1760-hcd.c > >+++ b/drivers/usb/host/isp1760-hcd.c > >@@ -18,6 +18,8 @@ > > #include <linux/uaccess.h> > > #include <linux/io.h> > > #include <asm/unaligned.h> > >+#include <asm/cacheflush.h> > >+#include <asm/memory.h> > > I'm fine with the patch generally but I don't like the asm headers. > cacheflush.h is available on most architectures as far as I can see it but > memory.h is only available on arm. So you break the build on !arm and > therefore I NAK this. Yes, that was already pointed out. I'll post a revised patch (until we maybe get a better API for such things but that's for linux-arch). Thanks. -- Catalin -- 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
