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 <kishon@xxxxxx>
Cc: Peter Ujfalusi <peter.ujfalusi@xxxxxx>
Cc: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
Reported-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
Signed-off-by: Tony Lindgren <tony@xxxxxxxxxxx>
---
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));
+
+ if (host->max_seg_size <= max_seg_size)
+ return;
+
+ dev_info(mmc_dev(host), "Lowering max_seg_size for DMA: %u vs %u\n",
+ host->max_seg_size, max_seg_size);
+
+ host->max_seg_size = max_seg_size;
+}
+
/**
* mmc_add_host - initialise host hardware
* @host: mmc host
@@ -430,6 +444,8 @@ int mmc_add_host(struct mmc_host *host)
WARN_ON((host->caps & MMC_CAP_SDIO_IRQ) &&
!host->ops->enable_sdio_irq);
+ mmc_check_max_seg_size(host);
+
err = device_add(&host->class_dev);
if (err)
return err;
--
2.19.1
