MMC host:

- renesas_sdhi: Fix build error in case NO_DMA=y
  - sdhci: Implement a bounce buffer to address throughput regressions
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Merge tag 'mmc-v4.16-2' of git://git.kernel.org/pub/scm/linux/kernel/git/ulfh/mmc

Pull MMC host fixes from Ulf Hansson:

 - renesas_sdhi: Fix build error in case NO_DMA=y

 - sdhci: Implement a bounce buffer to address throughput regressions

* tag 'mmc-v4.16-2' of git://git.kernel.org/pub/scm/linux/kernel/git/ulfh/mmc:
  mmc: MMC_SDHI_{SYS,INTERNAL}_DMAC should depend on HAS_DMA
  mmc: sdhci: Implement an SDHCI-specific bounce buffer

drivers/mmc/host/Kconfig

@@ -605,7 +605,7 @@ config MMC_SDHI
 
 config MMC_SDHI_SYS_DMAC
 	tristate "DMA for SDHI SD/SDIO controllers using SYS-DMAC"
-	depends on MMC_SDHI
+	depends on MMC_SDHI && HAS_DMA
 	default MMC_SDHI if (SUPERH || ARM)
 	help
 	  This provides DMA support for SDHI SD/SDIO controllers
@@ -615,7 +615,7 @@ config MMC_SDHI_SYS_DMAC
 config MMC_SDHI_INTERNAL_DMAC
 	tristate "DMA for SDHI SD/SDIO controllers using on-chip bus mastering"
 	depends on ARM64 || COMPILE_TEST
-	depends on MMC_SDHI
+	depends on MMC_SDHI && HAS_DMA
 	default MMC_SDHI if ARM64
 	help
 	  This provides DMA support for SDHI SD/SDIO controllers

drivers/mmc/host/sdhci.c

@@ -21,6 +21,7 @@
 #include <linux/dma-mapping.h>
 #include <linux/slab.h>
 #include <linux/scatterlist.h>
+#include <linux/sizes.h>
 #include <linux/swiotlb.h>
 #include <linux/regulator/consumer.h>
 #include <linux/pm_runtime.h>
@@ -502,8 +503,35 @@ static int sdhci_pre_dma_transfer(struct sdhci_host *host,
 	if (data->host_cookie == COOKIE_PRE_MAPPED)
 		return data->sg_count;
 
-	sg_count = dma_map_sg(mmc_dev(host->mmc), data->sg, data->sg_len,
-			      mmc_get_dma_dir(data));
+	/* Bounce write requests to the bounce buffer */
+	if (host->bounce_buffer) {
+		unsigned int length = data->blksz * data->blocks;
+
+		if (length > host->bounce_buffer_size) {
+			pr_err("%s: asked for transfer of %u bytes exceeds bounce buffer %u bytes\n",
+			       mmc_hostname(host->mmc), length,
+			       host->bounce_buffer_size);
+			return -EIO;
+		}
+		if (mmc_get_dma_dir(data) == DMA_TO_DEVICE) {
+			/* Copy the data to the bounce buffer */
+			sg_copy_to_buffer(data->sg, data->sg_len,
+					  host->bounce_buffer,
+					  length);
+		}
+		/* Switch ownership to the DMA */
+		dma_sync_single_for_device(host->mmc->parent,
+					   host->bounce_addr,
+					   host->bounce_buffer_size,
+					   mmc_get_dma_dir(data));
+		/* Just a dummy value */
+		sg_count = 1;
+	} else {
+		/* Just access the data directly from memory */
+		sg_count = dma_map_sg(mmc_dev(host->mmc),
+				      data->sg, data->sg_len,
+				      mmc_get_dma_dir(data));
+	}
 
 	if (sg_count == 0)
 		return -ENOSPC;
@@ -673,6 +701,14 @@ static void sdhci_adma_table_post(struct sdhci_host *host,
 	}
 }
 
+static u32 sdhci_sdma_address(struct sdhci_host *host)
+{
+	if (host->bounce_buffer)
+		return host->bounce_addr;
+	else
+		return sg_dma_address(host->data->sg);
+}
+
 static u8 sdhci_calc_timeout(struct sdhci_host *host, struct mmc_command *cmd)
 {
 	u8 count;
@@ -858,8 +894,8 @@ static void sdhci_prepare_data(struct sdhci_host *host, struct mmc_command *cmd)
 					     SDHCI_ADMA_ADDRESS_HI);
 		} else {
 			WARN_ON(sg_cnt != 1);
-			sdhci_writel(host, sg_dma_address(data->sg),
-				SDHCI_DMA_ADDRESS);
+			sdhci_writel(host, sdhci_sdma_address(host),
+				     SDHCI_DMA_ADDRESS);
 		}
 	}
 
@@ -2255,7 +2291,12 @@ static void sdhci_pre_req(struct mmc_host *mmc, struct mmc_request *mrq)
 
 	mrq->data->host_cookie = COOKIE_UNMAPPED;
 
-	if (host->flags & SDHCI_REQ_USE_DMA)
+	/*
+	 * No pre-mapping in the pre hook if we're using the bounce buffer,
+	 * for that we would need two bounce buffers since one buffer is
+	 * in flight when this is getting called.
+	 */
+	if (host->flags & SDHCI_REQ_USE_DMA && !host->bounce_buffer)
 		sdhci_pre_dma_transfer(host, mrq->data, COOKIE_PRE_MAPPED);
 }
 
@@ -2359,8 +2400,45 @@ static bool sdhci_request_done(struct sdhci_host *host)
 		struct mmc_data *data = mrq->data;
 
 		if (data && data->host_cookie == COOKIE_MAPPED) {
-			dma_unmap_sg(mmc_dev(host->mmc), data->sg, data->sg_len,
-				     mmc_get_dma_dir(data));
+			if (host->bounce_buffer) {
+				/*
+				 * On reads, copy the bounced data into the
+				 * sglist
+				 */
+				if (mmc_get_dma_dir(data) == DMA_FROM_DEVICE) {
+					unsigned int length = data->bytes_xfered;
+
+					if (length > host->bounce_buffer_size) {
+						pr_err("%s: bounce buffer is %u bytes but DMA claims to have transferred %u bytes\n",
+						       mmc_hostname(host->mmc),
+						       host->bounce_buffer_size,
+						       data->bytes_xfered);
+						/* Cap it down and continue */
+						length = host->bounce_buffer_size;
+					}
+					dma_sync_single_for_cpu(
+						host->mmc->parent,
+						host->bounce_addr,
+						host->bounce_buffer_size,
+						DMA_FROM_DEVICE);
+					sg_copy_from_buffer(data->sg,
+						data->sg_len,
+						host->bounce_buffer,
+						length);
+				} else {
+					/* No copying, just switch ownership */
+					dma_sync_single_for_cpu(
+						host->mmc->parent,
+						host->bounce_addr,
+						host->bounce_buffer_size,
+						mmc_get_dma_dir(data));
+				}
+			} else {
+				/* Unmap the raw data */
+				dma_unmap_sg(mmc_dev(host->mmc), data->sg,
+					     data->sg_len,
+					     mmc_get_dma_dir(data));
+			}
 			data->host_cookie = COOKIE_UNMAPPED;
 		}
 	}
@@ -2643,7 +2721,8 @@ static void sdhci_data_irq(struct sdhci_host *host, u32 intmask)
 		 */
 		if (intmask & SDHCI_INT_DMA_END) {
 			u32 dmastart, dmanow;
-			dmastart = sg_dma_address(host->data->sg);
+
+			dmastart = sdhci_sdma_address(host);
 			dmanow = dmastart + host->data->bytes_xfered;
 			/*
 			 * Force update to the next DMA block boundary.
@@ -3234,6 +3313,68 @@ void __sdhci_read_caps(struct sdhci_host *host, u16 *ver, u32 *caps, u32 *caps1)
 }
 EXPORT_SYMBOL_GPL(__sdhci_read_caps);
 
+static int sdhci_allocate_bounce_buffer(struct sdhci_host *host)
+{
+	struct mmc_host *mmc = host->mmc;
+	unsigned int max_blocks;
+	unsigned int bounce_size;
+	int ret;
+
+	/*
+	 * Cap the bounce buffer at 64KB. Using a bigger bounce buffer
+	 * has diminishing returns, this is probably because SD/MMC
+	 * cards are usually optimized to handle this size of requests.
+	 */
+	bounce_size = SZ_64K;
+	/*
+	 * Adjust downwards to maximum request size if this is less
+	 * than our segment size, else hammer down the maximum
+	 * request size to the maximum buffer size.
+	 */
+	if (mmc->max_req_size < bounce_size)
+		bounce_size = mmc->max_req_size;
+	max_blocks = bounce_size / 512;
+
+	/*
+	 * When we just support one segment, we can get significant
+	 * speedups by the help of a bounce buffer to group scattered
+	 * reads/writes together.
+	 */
+	host->bounce_buffer = devm_kmalloc(mmc->parent,
+					   bounce_size,
+					   GFP_KERNEL);
+	if (!host->bounce_buffer) {
+		pr_err("%s: failed to allocate %u bytes for bounce buffer, falling back to single segments\n",
+		       mmc_hostname(mmc),
+		       bounce_size);
+		/*
+		 * Exiting with zero here makes sure we proceed with
+		 * mmc->max_segs == 1.
+		 */
+		return 0;
+	}
+
+	host->bounce_addr = dma_map_single(mmc->parent,
+					   host->bounce_buffer,
+					   bounce_size,
+					   DMA_BIDIRECTIONAL);
+	ret = dma_mapping_error(mmc->parent, host->bounce_addr);
+	if (ret)
+		/* Again fall back to max_segs == 1 */
+		return 0;
+	host->bounce_buffer_size = bounce_size;
+
+	/* Lie about this since we're bouncing */
+	mmc->max_segs = max_blocks;
+	mmc->max_seg_size = bounce_size;
+	mmc->max_req_size = bounce_size;
+
+	pr_info("%s bounce up to %u segments into one, max segment size %u bytes\n",
+		mmc_hostname(mmc), max_blocks, bounce_size);
+
+	return 0;
+}
+
 int sdhci_setup_host(struct sdhci_host *host)
 {
 	struct mmc_host *mmc;
@@ -3730,6 +3871,13 @@ int sdhci_setup_host(struct sdhci_host *host)
 	 */
 	mmc->max_blk_count = (host->quirks & SDHCI_QUIRK_NO_MULTIBLOCK) ? 1 : 65535;
 
+	if (mmc->max_segs == 1) {
+		/* This may alter mmc->*_blk_* parameters */
+		ret = sdhci_allocate_bounce_buffer(host);
+		if (ret)
+			return ret;
+	}
+
 	return 0;
 
 unreg:

drivers/mmc/host/sdhci.h

@@ -440,6 +440,9 @@ struct sdhci_host {
 
 	int irq;		/* Device IRQ */
 	void __iomem *ioaddr;	/* Mapped address */
+	char *bounce_buffer;	/* For packing SDMA reads/writes */
+	dma_addr_t bounce_addr;
+	unsigned int bounce_buffer_size;
 
 	const struct sdhci_ops *ops;	/* Low level hw interface */