* Ulf Hansson [off-list ref] [181119 12:09]:

On 31 October 2018 at 16:57, Tony Lindgren [off-list ref] wrote:

quoted

With CONFIG_DMA_API_DEBUG_SG a device may produce the following warning:

"DMA-API: mapping sg segment longer than device claims to support"

We default to 64KiB if a DMA engine driver does not initialize dma_parms
and call dma_set_max_seg_size(). This may be lower that what many MMC
drivers do with mmc->max_seg_size = mmc->max_blk_size * mmc->max_blk_count.

Let's do a sanity check for max_seg_size being higher than what DMA
supports in mmc_add_host() and lower it as needed.

Cc: Kishon Vijay Abraham I <redacted>
Cc: Peter Ujfalusi <redacted>
Cc: Russell King <redacted>
Reported-by: Russell King <redacted>
Signed-off-by: Tony Lindgren <tony@atomide.com>
---
 drivers/mmc/core/host.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
--- a/drivers/mmc/core/host.c
+++ b/drivers/mmc/core/host.c

@@ -13,6 +13,7 @@
  */

 #include <linux/device.h>
+#include <linux/dma-mapping.h>
 #include <linux/err.h>
 #include <linux/idr.h>
 #include <linux/of.h>

@@ -415,6 +416,19 @@ struct mmc_host *mmc_alloc_host(int extra, struct device *dev)

 EXPORT_SYMBOL(mmc_alloc_host);

+static void mmc_check_max_seg_size(struct mmc_host *host)
+{
+       unsigned int max_seg_size = dma_get_max_seg_size(mmc_dev(host));

Is dma_get_max_seg_size() really intended to be called for any struct
device (representing the mmc controller) like this?

My understanding is that the dma_get_max_seg_size() is supposed to be
called by using the DMA engine device, no?

Oh good catch sounds like I'm calling it for the wrong device,
need to check. In that case sounds like this can't be generic?

Regards,

Tony

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel