[PATCH] mmc: dw_mmc: take SWIOTLB memory size limitation into account

[Aurelien Jarno]

The Synopsys DesignWare mmc controller on the JH7110 SoC
(dw_mmc-starfive.c driver) is using a 32-bit IDMAC address bus width,
and thus requires the use of SWIOTLB.

The commit 8396c793ffdf ("mmc: dw_mmc: Fix IDMAC operation with pages
bigger than 4K") increased the max_seq_size, even for 4K pages, causing
"swiotlb buffer is full" to happen because swiotlb can only handle a
memory size up to 256kB only.

Fix the issue, by making sure the dw_mmc driver doesn't use segments
bigger than what SWIOTLB can handle.

Reported-by: Ron Economos <re at w6rz.net>
Reported-by: Jing Luo <jing at jing.rocks>
Fixes: 8396c793ffdf ("mmc: dw_mmc: Fix IDMAC operation with pages bigger than 4K")
Cc: stable at vger.kernel.org
Signed-off-by: Aurelien Jarno <aurelien at aurel32.net>
---
 drivers/mmc/host/dw_mmc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 41e451235f637..dc0d6201f7b73 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -2958,7 +2958,8 @@ static int dw_mci_init_slot(struct dw_mci *host)
 		mmc->max_segs = host->ring_size;
 		mmc->max_blk_size = 65535;
 		mmc->max_req_size = DW_MCI_DESC_DATA_LENGTH * host->ring_size;
-		mmc->max_seg_size = mmc->max_req_size;
+		mmc->max_seg_size =
+		    min_t(size_t, mmc->max_req_size, dma_max_mapping_size(host->dev));
 		mmc->max_blk_count = mmc->max_req_size / 512;
 	} else if (host->use_dma == TRANS_MODE_EDMAC) {
 		mmc->max_segs = 64;
-- 
2.45.2