From 8f7f6b7e46117edb83d12a508fffa0f013457677 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Fri, 24 Feb 2012 11:25:21 +0000 Subject: [PATCH] mmc: mmci: reduce max_blk_count to avoid overflowing max_req_size 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] [] dump_backtrace+0x0/0x120 [ 2.338317] [] dump_stack+0x14/0x1c [ 2.338403] [] panic+0xbc/0x1f0 [ 2.338498] [] mmc_start_request+0x154/0x184 [ 2.338600] [] mmc_start_req+0x110/0x140 [ 2.338701] [] mmc_blk_issue_rw_rq+0x7c/0x39c [ 2.338804] [] mmc_blk_issue_rq+0x1c0/0x468 [ 2.338905] [] mmc_queue_thread+0x68/0x118 [ 2.338995] [] 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. Signed-off-by: Will Deacon Signed-off-by: Chris Ball --- drivers/mmc/host/mmci.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c index 0d955ffaf44e..11e589cd8233 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); -- 2.11.0