On Thu, Aug 13, 2009 at 10:16 AM, Seth Forshee <[email protected]>wrote:
> > On Wed, Aug 12, 2009 at 09:14:36AM -0700, San Mehat wrote: > > On Tue, Jul 28, 2009 at 7:59 AM, Seth Forshee <[email protected] > >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. > Ahhh yes, that could explain the differences - we're running with BLOCK_BOUNCE disabled. I'll try it that way in a few days -san > > 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 > > > > -- ---------- San Mehat Staff Software Engineer Google Inc. o: 650-253-7422 c: 408-382-1249 [email protected] --~--~---------~--~----~------------~-------~--~----~ unsubscribe: [email protected] website: http://groups.google.com/group/android-kernel -~----------~----~----~----~------~----~------~--~---
