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 -- 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
