We must use a 64-bit for this, otherwise overflowed bits get lost, and
that can result in a lower than intended value set.
Fixes: 8e0cb8a1f6ac ("ARM: 7797/1: mmc: Use dma_max_pfn(dev) helper for bounce_limit calculations")
Fixes: 7d35496dd982 ("ARM: 7796/1: scsi: Use dma_max_pfn(dev) helper for bounce_limit calculations")
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
---
While poking about with the Cubox-i4 and investigating why my UHS-1
SD card wasn't achieving its full potential, I came across a slight
problem... the SDHCI host sets a mask of 0xffffffff, but with the
start of memory at pfn 0x10000, the blk code sees this when setting
the bounce limit:
max addr 0x0ffff000 bounce limit 0xffff dma 1
and this results in the bounce functions appearing in the profile:
00000000c00f8b70 copy_to_high_bio_irq 1139 2.5886
00000000c00f8d28 bounce_end_io 12 0.0714
00000000c00f8dd0 bounce_end_io_read_isa 8 0.1053
which, compared to the cost of copying the data to userland and
request handling, this is quite significant:
00000000c04b1794 sdhci_request 268 0.5447
00000000c02d0740 __copy_to_user_std 398 0.4252
With this calculation fixed, we avoid the bouncing code entirely.
max addr 0x10ffff000 bounce limit 0x10ffff dma 0
drivers/mmc/card/queue.c | 2 +-
drivers/scsi/scsi_lib.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/mmc/card/queue.c b/drivers/mmc/card/queue.c
index 357bbc54fe4b..3e049c13429c 100644
--- a/drivers/mmc/card/queue.c
+++ b/drivers/mmc/card/queue.c
@@ -197,7 +197,7 @@ int mmc_init_queue(struct mmc_queue *mq, struct mmc_card *card,
struct mmc_queue_req *mqrq_prev = &mq->mqrq[1];
if (mmc_dev(host)->dma_mask && *mmc_dev(host)->dma_mask)
- limit = dma_max_pfn(mmc_dev(host)) << PAGE_SHIFT;
+ limit = (u64)dma_max_pfn(mmc_dev(host)) << PAGE_SHIFT;
mq->card = card;
mq->queue = blk_init_queue(mmc_request_fn, lock);
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 7bd7f0d5f050..62ec84b42e31 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1684,7 +1684,7 @@ u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost)
host_dev = scsi_get_device(shost);
if (host_dev && host_dev->dma_mask)
- bounce_limit = dma_max_pfn(host_dev) << PAGE_SHIFT;
+ bounce_limit = (u64)dma_max_pfn(host_dev) << PAGE_SHIFT;
return bounce_limit;
}
--
1.8.3.1
--
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