[PATCH] mmc: core: Lower max_seg_size if too high for DMA
STALE2854d
From: tony@atomide.com (Tony Lindgren)
Date: 2018-10-31 15:57:38
Also in:
linux-mmc, linux-omap
Subsystem:
multimedia card (mmc), secure digital (sd) and sdio subsystem, the rest · Maintainers:
Ulf Hansson, Linus Torvalds
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)); + + 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