[adding Pierre with the correct email address] On Fri, Feb 24, 2012 at 11:25:21AM +0000, Will Deacon wrote: > On a system with large pages (64k in my case), the following BUG is > triggered in MMC core: > > [ 2.338023] BUG: failure at drivers/mmc/core/core.c:221/mmc_start_request()! > [ 2.338102] Kernel panic - not syncing: BUG! > [ 2.338155] Call trace: > [ 2.338228] [<ffffffc00008635c>] dump_backtrace+0x0/0x120 > [ 2.338317] [<ffffffc0003365ec>] dump_stack+0x14/0x1c > [ 2.338403] [<ffffffc000336990>] panic+0xbc/0x1f0 > [ 2.338498] [<ffffffc00027a494>] mmc_start_request+0x154/0x184 > [ 2.338600] [<ffffffc00027abdc>] mmc_start_req+0x110/0x140 > [ 2.338701] [<ffffffc00028604c>] mmc_blk_issue_rw_rq+0x7c/0x39c > [ 2.338804] [<ffffffc00028652c>] mmc_blk_issue_rq+0x1c0/0x468 > [ 2.338905] [<ffffffc000287564>] mmc_queue_thread+0x68/0x118 > [ 2.338995] [<ffffffc0000bc308>] kthread+0x84/0x8c > > This is because of a 64k request with a max_req_size of 64k-1 bytes. > > The following patch fixes the problem by limiting the max_blk_count > such that max_blk_count * max_blk_size == max_req_size. I couldn't > pursuade the compiler to emit a shift instead of a div without encoding > the shift explicitly. > > Cc: Pierre Ossman <drzeus@xxxxxxxxx> > Cc: Chris Ball <cjb@xxxxxxxxxx> > Signed-off-by: Will Deacon <will.deacon@xxxxxxx> > --- > drivers/mmc/host/mmci.c | 7 ++++--- > 1 files changed, 4 insertions(+), 3 deletions(-) > > diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c > index 0d955ff..11e589c 100644 > --- a/drivers/mmc/host/mmci.c > +++ b/drivers/mmc/host/mmci.c > @@ -1271,12 +1271,13 @@ static int __devinit mmci_probe(struct amba_device *dev, > /* > * Block size can be up to 2048 bytes, but must be a power of two. > */ > - mmc->max_blk_size = 2048; > + mmc->max_blk_size = 1 << 11; > > /* > - * No limit on the number of blocks transferred. > + * Limit the number of blocks transferred so that we don't overflow > + * the maximum request size. > */ > - mmc->max_blk_count = mmc->max_req_size; > + mmc->max_blk_count = mmc->max_req_size >> 11; > > spin_lock_init(&host->lock); > > -- > 1.7.4.1 Any thoughts on this? I'm by no means an MMC expert, so I'm open to suggestions if there's a more suitable fix. Cheers, Will -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
