On Wed, Aug 12, 2009 at 09:14:36AM -0700, San Mehat wrote: > On Tue, Jul 28, 2009 at 7:59 AM, Seth Forshee <seth.fors...@gmail.com>wrote: > > > > > On Tue, Jul 28, 2009 at 07:34:14AM -0700, San Mehat wrote: > > > I'll try your test code when I have a chance. > > > > Thanks. > > > > > > I'm in a difficult debugging sitation for this issue. I can't build > > the > > > > kernel for the device (I'm working on getting the source to allow me to > > > > do this), and I don't have documentation for the processor. I also > > > > don't know whether the msm_sdcc driver is using DMA or PIO for the > > > > transfer, although in my tracing of the code paths it doesn't look like > > > > it should matter because in either case the cache lines for the > > > > userspace mapping should be cleaned and invalidated before the transfer > > > > starts. Are there any peculiarities of Android kernel modifications or > > > > of the MSM7k that could be causing this sort of behavior? > > > > > > > > > > > Just an update on this, I've run your test program on a number of devices > with a few different brands of sdcards and haven't had a single failure. > Perhaps your unit is somehow faulty?
Interesting. I'll see if I can get another board to test with. I haven't been involved with kernel development on this device, but looking now it's pretty obvious that some changes have been made to the MSM MMC driver. Maybe I'll see exactly what changes were made. I also noticed that CONFIG_MMC_BLOCK_BOUNCE is enabled in the kernel config for this device. Was that enabled during your tests? I haven't had time to look in detail, but it looks like the end result is that the data is copied to a kmalloc-ed buffer, and I/O is done from there. That adds more opportunity for aliasing, I suppose. I've had to push this aside for a while, but I'll try to make some time in the next few days to try out some of these things. Thanks for your help. Cheers, Seth --~--~---------~--~----~------------~-------~--~----~ unsubscribe: android-kernel+unsubscr...@googlegroups.com website: http://groups.google.com/group/android-kernel -~----------~----~----~----~------~----~------~--~---
