[PATCH v2 1/3] mmc: sdhci: add support for using external DMA devices

[Chunyan Zhang]

Some standard SD host controllers can support both external dma
controllers as well as ADMA/SDMA in which the SD host controller
acts as DMA master. TI's omap controller is the case as an example.

Currently the generic SDHCI code supports ADMA/SDMA integrated in
the host controller but does not have any support for external DMA
controllers implemented using dmaengine, meaning that custom code is
needed for any systems that use an external DMA controller with SDHCI.

Signed-off-by: Chunyan Zhang <zhang.chunyan@xxxxxxxxxx>
---
 drivers/mmc/host/Kconfig |  13 ++++
 drivers/mmc/host/sdhci.c | 181 ++++++++++++++++++++++++++++++++++++++++++++++-
 drivers/mmc/host/sdhci.h |   8 +++
 3 files changed, 201 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig
index 1b58739..7bf3eff 100644
--- a/drivers/mmc/host/Kconfig
+++ b/drivers/mmc/host/Kconfig
@@ -977,3 +977,16 @@ config MMC_SDHCI_OMAP
 	  If you have a controller with this interface, say Y or M here.
 
 	  If unsure, say N.
+
+config MMC_SDHCI_EXTERNAL_DMA
+        bool "Support external DMA in standard SD host controller"
+	depends on MMC_SDHCI
+	depends on DMA_ENGINE
+	help
+	  This is an option for using external DMA device via dmaengine
+	  framework.
+
+	  If you have a controller which support using external DMA device
+	  for data transfer, can say Y.
+
+	  If unsure, say N.
diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 99bdae5..853cc98 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -14,6 +14,7 @@
  */
 
 #include <linux/delay.h>
+#include <linux/dmaengine.h>
 #include <linux/ktime.h>
 #include <linux/highmem.h>
 #include <linux/io.h>
@@ -1309,6 +1310,158 @@ static void sdhci_del_timer(struct sdhci_host *host, struct mmc_request *mrq)
 		del_timer(&host->timer);
 }
 
+#if IS_ENABLED(CONFIG_MMC_SDHCI_EXTERNAL_DMA)
+static int sdhci_external_dma_init(struct sdhci_host *host)
+{
+	int ret = 0;
+	struct mmc_host *mmc = host->mmc;
+
+	host->tx_chan = dma_request_chan(mmc->parent, "tx");
+	if (IS_ERR(host->tx_chan)) {
+		ret = PTR_ERR(host->tx_chan);
+		if (ret != -EPROBE_DEFER)
+			pr_warn("Failed to request TX DMA channel.\n");
+		host->tx_chan = NULL;
+		return ret;
+	}
+
+	host->rx_chan = dma_request_chan(mmc->parent, "rx");
+	if (IS_ERR(host->rx_chan)) {
+		if (host->tx_chan) {
+			dma_release_channel(host->tx_chan);
+			host->tx_chan = NULL;
+		}
+
+		ret = PTR_ERR(host->rx_chan);
+		if (ret != -EPROBE_DEFER)
+			pr_warn("Failed to request RX DMA channel.\n");
+		host->rx_chan = NULL;
+	}
+
+	return ret;
+}
+
+static inline struct dma_chan *
+sdhci_external_dma_channel(struct sdhci_host *host, struct mmc_data *data)
+{
+	return data->flags & MMC_DATA_WRITE ? host->tx_chan : host->rx_chan;
+}
+
+static int sdhci_external_dma_setup(struct sdhci_host *host,
+				    struct mmc_command *cmd)
+{
+	int ret = 0, i;
+	struct dma_async_tx_descriptor *desc;
+	struct mmc_data *data = cmd->data;
+	struct dma_chan *chan;
+	struct dma_slave_config cfg;
+	dma_cookie_t cookie;
+
+	if (!host->mapbase)
+		return -EINVAL;
+
+	cfg.src_addr = host->mapbase + SDHCI_BUFFER;
+	cfg.dst_addr = host->mapbase + SDHCI_BUFFER;
+	cfg.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
+	cfg.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
+	cfg.src_maxburst = data->blksz / 4;
+	cfg.dst_maxburst = data->blksz / 4;
+
+	/* Sanity check: all the SG entries must be aligned by block size. */
+	for (i = 0; i < data->sg_len; i++) {
+		if ((data->sg + i)->length % data->blksz)
+			return -EINVAL;
+	}
+
+	chan = sdhci_external_dma_channel(host, data);
+
+	ret = dmaengine_slave_config(chan, &cfg);
+	if (ret)
+		return ret;
+
+	desc = dmaengine_prep_slave_sg(chan, data->sg, data->sg_len,
+				       mmc_get_dma_dir(data),
+				       DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+	if (!desc)
+		return -EINVAL;
+
+	desc->callback = NULL;
+	desc->callback_param = NULL;
+
+	cookie = dmaengine_submit(desc);
+	if (cookie < 0)
+		ret = cookie;
+
+	return ret;
+}
+
+static void sdhci_external_dma_release(struct sdhci_host *host)
+{
+	if (host->tx_chan) {
+		dma_release_channel(host->tx_chan);
+		host->tx_chan = NULL;
+	}
+
+	if (host->rx_chan) {
+		dma_release_channel(host->rx_chan);
+		host->rx_chan = NULL;
+	}
+
+	sdhci_switch_external_dma(host, false);
+}
+
+static void sdhci_external_dma_prepare_data(struct sdhci_host *host,
+					    struct mmc_command *cmd)
+{
+	if (sdhci_external_dma_setup(host, cmd)) {
+		sdhci_external_dma_release(host);
+		pr_err("%s: Failed to setup external DMA, switch to the DMA/PIO which standard SDHCI provides.\n",
+		       mmc_hostname(host->mmc));
+	} else {
+		/* Prepare for using external dma */
+		host->flags |= SDHCI_REQ_USE_DMA;
+	}
+
+	sdhci_prepare_data(host, cmd);
+}
+
+static void sdhci_external_dma_pre_transfer(struct sdhci_host *host,
+					    struct mmc_command *cmd)
+{
+	struct dma_chan *chan = sdhci_external_dma_channel(host, cmd->data);
+
+	if (cmd->opcode != MMC_SET_BLOCK_COUNT) {
+		sdhci_set_timeout(host, cmd);
+		dma_async_issue_pending(chan);
+	}
+}
+#else
+static int sdhci_external_dma_init(struct sdhci_host *host)
+{
+	return 0;
+}
+
+static void sdhci_external_dma_release(struct sdhci_host *host)
+{}
+
+static void sdhci_external_dma_prepare_data(struct sdhci_host *host,
+					    struct mmc_command *cmd)
+{
+	/* If SDHCI_EXTDMA not supported, PIO will be used */
+	sdhci_prepare_data(host, cmd);
+}
+
+static void sdhci_external_dma_pre_transfer(struct sdhci_host *host,
+					    struct mmc_command *cmd)
+{}
+#endif
+
+void sdhci_switch_external_dma(struct sdhci_host *host, bool en)
+{
+	host->use_external_dma = en;
+}
+EXPORT_SYMBOL_GPL(sdhci_switch_external_dma);
+
 void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
 {
 	int flags;
@@ -1355,7 +1508,10 @@ void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
 		host->data_cmd = cmd;
 	}
 
-	sdhci_prepare_data(host, cmd);
+	if (host->use_external_dma)
+		sdhci_external_dma_prepare_data(host, cmd);
+	else
+		sdhci_prepare_data(host, cmd);
 
 	sdhci_writel(host, cmd->arg, SDHCI_ARGUMENT);
 
@@ -1397,6 +1553,9 @@ void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
 		timeout += 10 * HZ;
 	sdhci_mod_timer(host, cmd->mrq, timeout);
 
+	if (host->use_external_dma)
+		sdhci_external_dma_pre_transfer(host, cmd);
+
 	sdhci_writew(host, SDHCI_MAKE_CMD(cmd->opcode, flags), SDHCI_COMMAND);
 }
 EXPORT_SYMBOL_GPL(sdhci_send_command);
@@ -4133,6 +4292,19 @@ int sdhci_setup_host(struct sdhci_host *host)
 			return ret;
 	}
 
+	if (host->use_external_dma) {
+		ret = sdhci_external_dma_init(host);
+		if (ret == -EPROBE_DEFER)
+			goto unreg;
+
+		/*
+		 * Fall back to use the DMA/PIO integrated in standard SDHCI
+		 * instead of external DMA devices.
+		 */
+		if (ret)
+			sdhci_switch_external_dma(host, false);
+	}
+
 	return 0;
 
 unreg:
@@ -4161,6 +4333,10 @@ void sdhci_cleanup_host(struct sdhci_host *host)
 		dma_free_coherent(mmc_dev(mmc), host->align_buffer_sz +
 				  host->adma_table_sz, host->align_buffer,
 				  host->align_addr);
+
+	if (host->use_external_dma)
+		sdhci_external_dma_release(host);
+
 	host->adma_table = NULL;
 	host->align_buffer = NULL;
 }
@@ -4295,6 +4471,9 @@ void sdhci_remove_host(struct sdhci_host *host, int dead)
 				  host->adma_table_sz, host->align_buffer,
 				  host->align_addr);
 
+	if (host->use_external_dma)
+		sdhci_external_dma_release(host);
+
 	host->adma_table = NULL;
 	host->align_buffer = NULL;
 }
diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
index b001cf4..8e50a97 100644
--- a/drivers/mmc/host/sdhci.h
+++ b/drivers/mmc/host/sdhci.h
@@ -475,6 +475,7 @@ struct sdhci_host {
 
 	int irq;		/* Device IRQ */
 	void __iomem *ioaddr;	/* Mapped address */
+	phys_addr_t mapbase;	/* physical address base */
 	char *bounce_buffer;	/* For packing SDMA reads/writes */
 	dma_addr_t bounce_addr;
 	unsigned int bounce_buffer_size;
@@ -524,6 +525,7 @@ struct sdhci_host {
 	bool pending_reset;	/* Cmd/data reset is pending */
 	bool irq_wake_enabled;	/* IRQ wakeup is enabled */
 	bool v4_mode;		/* Host Version 4 Enable */
+	bool use_external_dma;
 
 	struct mmc_request *mrqs_done[SDHCI_MAX_MRQS];	/* Requests done */
 	struct mmc_command *cmd;	/* Current command */
@@ -552,6 +554,11 @@ struct sdhci_host {
 	struct timer_list timer;	/* Timer for timeouts */
 	struct timer_list data_timer;	/* Timer for data timeouts */
 
+#if IS_ENABLED(CONFIG_MMC_SDHCI_EXTERNAL_DMA)
+	struct dma_chan	*rx_chan;
+	struct dma_chan	*tx_chan;
+#endif
+
 	u32 caps;		/* CAPABILITY_0 */
 	u32 caps1;		/* CAPABILITY_1 */
 	bool read_caps;		/* Capability flags have been read */
@@ -785,5 +792,6 @@ void sdhci_start_tuning(struct sdhci_host *host);
 void sdhci_end_tuning(struct sdhci_host *host);
 void sdhci_reset_tuning(struct sdhci_host *host);
 void sdhci_send_tuning(struct sdhci_host *host, u32 opcode);
+void sdhci_switch_external_dma(struct sdhci_host *host, bool en);
 
 #endif /* __SDHCI_HW_H */
-- 
2.7.4