[PATCH v2 3/5] dmaengine: aspeed: Add AST2600 UART DMA driver

[Chia-Wei Wang]

Aspeed AST2600 UART DMA (UDMA) includes 14 channels for the
DMA transmission and recevie of each UART devices.

Signed-off-by: Chia-Wei Wang <chiawei_wang@xxxxxxxxxxxxxx>
---
 drivers/dma/Kconfig        |   9 +
 drivers/dma/Makefile       |   1 +
 drivers/dma/ast2600-udma.c | 528 +++++++++++++++++++++++++++++++++++++
 3 files changed, 538 insertions(+)
 create mode 100644 drivers/dma/ast2600-udma.c

diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
index fb7073fc034f..c35f87dbafd9 100644
--- a/drivers/dma/Kconfig
+++ b/drivers/dma/Kconfig
@@ -748,6 +748,15 @@ config XILINX_ZYNQMP_DPDMA
 	  driver provides the dmaengine required by the DisplayPort subsystem
 	  display driver.
 
+config ASPEED_AST2600_UDMA
+	bool "Aspeed AST2600 UDMA support"
+	depends on ARCH_ASPEED
+	help
+	  Enable support for Aspeed AST2600 UART DMA. Select this option if you
+	  have a AST2600 SoC integrated system. The driver provides the UART DMA
+	  support with the dmaengine subsystem, which can be leveraged by generic
+	  8250 serial drivers.
+
 # driver files
 source "drivers/dma/bestcomm/Kconfig"
 
diff --git a/drivers/dma/Makefile b/drivers/dma/Makefile
index a4fd1ce29510..6cbacebcdcab 100644
--- a/drivers/dma/Makefile
+++ b/drivers/dma/Makefile
@@ -81,6 +81,7 @@ obj-$(CONFIG_XGENE_DMA) += xgene-dma.o
 obj-$(CONFIG_ST_FDMA) += st_fdma.o
 obj-$(CONFIG_FSL_DPAA2_QDMA) += fsl-dpaa2-qdma/
 obj-$(CONFIG_INTEL_LDMA) += lgm/
+obj-$(CONFIG_ASPEED_AST2600_UDMA) += ast2600-udma.o
 
 obj-y += mediatek/
 obj-y += qcom/
diff --git a/drivers/dma/ast2600-udma.c b/drivers/dma/ast2600-udma.c
new file mode 100644
index 000000000000..ff678724f9d9
--- /dev/null
+++ b/drivers/dma/ast2600-udma.c
@@ -0,0 +1,528 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) ASPEED Technology Inc.
+ */
+#include <linux/delay.h>
+#include <linux/bitfield.h>
+#include <linux/interrupt.h>
+#include <linux/dmaengine.h>
+#include <linux/dma-mapping.h>
+#include <linux/platform_device.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_dma.h>
+#include <linux/of_irq.h>
+#include <linux/of_address.h>
+#include <linux/dma-direct.h>
+#include "dmaengine.h"
+
+#define DEVICE_NAME	"aspeed-udma"
+
+/* register offset */
+#define UDMA_TX_EN		0x000
+#define UDMA_RX_EN		0x004
+#define UDMA_TMOUT		0x00c
+#define UDMA_TX_PTR_RST		0x020
+#define UDMA_RX_PTR_RST		0x024
+#define UDMA_TX_INT_EN		0x030
+#define UDMA_TX_INT_STS		0x034
+#define UDMA_RX_INT_EN		0x038
+#define UDMA_RX_INT_STS		0x03c
+
+#define UDMA_CH_OFFS(x)		((x) * 0x10)
+#define UDMA_CH_RPTR(x)		(0x040 + UDMA_CH_OFFS(x))
+#define UDMA_CH_WPTR(x)		(0x044 + UDMA_CH_OFFS(x))
+#define UDMA_CH_ADDR(x)		(0x048 + UDMA_CH_OFFS(x))
+#define UDMA_CH_CTRL(x)		(0x04c + UDMA_CH_OFFS(x))
+#define   UDMA_CH_CTRL_BUFSZ	GENMASK(1, 0)
+
+#define UDMA_MAX_BUFSZ	(0x10000)
+#define UDMA_MAX_TXSZ	(UDMA_MAX_BUFSZ - 1)
+
+enum ast2600_udma_bufsz {
+	UDMA_BUFSZ_1KB,
+	UDMA_BUFSZ_4KB,
+	UDMA_BUFSZ_16KB,
+	UDMA_BUFSZ_64KB,
+};
+
+struct ast2600_udma_desc {
+	struct dma_async_tx_descriptor tx;
+	dma_addr_t addr;
+	unsigned int size;
+};
+
+struct ast2600_udma_chan {
+	struct dma_chan chan;
+	struct ast2600_udma_desc ud;
+	struct ast2600_udma *udma;
+	uint32_t residue;
+
+	/* 4B-aligned local buffer for workaround */
+	uint8_t *buf;
+	dma_addr_t buf_addr;
+
+	bool is_tx;
+};
+
+struct ast2600_udma {
+	struct dma_device ddev;
+	uint8_t __iomem *regs;
+	int irq;
+	struct ast2600_udma_chan *ucs;
+	uint32_t n_ucs;
+	spinlock_t lock;
+};
+
+static struct ast2600_udma_chan *to_ast2600_udma_chan(struct dma_chan *chan)
+{
+	return container_of(chan, struct ast2600_udma_chan, chan);
+}
+
+static int ast2600_udma_alloc_chan_resources(struct dma_chan *chan)
+{
+	dma_cookie_init(chan);
+
+	return 0;
+}
+
+static dma_cookie_t ast2600_udma_tx_submit(struct dma_async_tx_descriptor *tx)
+{
+	return dma_cookie_assign(tx);
+}
+
+/* consider only 8250_dma using dmaengine_prep_slave_single() */
+static struct dma_async_tx_descriptor *ast2600_udma_prep_slave_sg(struct dma_chan *chan,
+								  struct scatterlist *sgl,
+								  unsigned int sg_len,
+								  enum dma_transfer_direction dir,
+								  unsigned long tx_flags,
+								  void *context)
+{
+	void *p;
+	struct device *dev = chan->device->dev;
+	struct ast2600_udma_chan *uc = to_ast2600_udma_chan(chan);
+	struct ast2600_udma_desc *ud = &uc->ud;
+
+	if (!is_slave_direction(dir)) {
+		dev_err(dev, "direction is not slave mode\n");
+		return NULL;
+	}
+
+	if (sg_len != 1) {
+		dev_err(dev, "scatter list length is not 1\n");
+		return NULL;
+	}
+
+	if (uc->is_tx && dir != DMA_MEM_TO_DEV) {
+		dev_err(dev, "invalid direction to TX channel\n");
+		return NULL;
+	}
+
+	ud->addr = sg_dma_address(sgl);
+	ud->size = sg_dma_len(sgl);
+
+	if (uc->is_tx) {
+		if (ud->size > UDMA_MAX_TXSZ) {
+			dev_err(dev, "invalid TX DMA SIZE");
+			return NULL;
+		}
+
+		/*
+		 * UDMA is limited to 4B-aligned DMA addresses.
+		 * Thus copy data to local 4B-aligned buffer if
+		 * the source does not fit.
+		 */
+		if (ud->addr & 0x3) {
+			p = phys_to_virt(dma_to_phys(chan->device->dev, ud->addr));
+			memcpy(uc->buf, p, ud->size);
+			ud->addr = uc->buf_addr;
+		}
+	} else {
+		/*
+		 * UDMA RX buffer size is limited to 1/4/16/64 KB
+		 * We use the lower bits to encode the buffer size
+		 */
+		switch (ud->size) {
+		case 0x400:
+			ud->size |= FIELD_PREP(UDMA_CH_CTRL_BUFSZ, UDMA_BUFSZ_1KB);
+			break;
+		case 0x1000:
+			ud->size |= FIELD_PREP(UDMA_CH_CTRL_BUFSZ, UDMA_BUFSZ_4KB);
+			break;
+		case 0x4000:
+			ud->size |= FIELD_PREP(UDMA_CH_CTRL_BUFSZ, UDMA_BUFSZ_16KB);
+			break;
+		case 0x10000:
+			ud->size |= FIELD_PREP(UDMA_CH_CTRL_BUFSZ, UDMA_BUFSZ_64KB);
+			break;
+		default:
+			dev_err(dev, "invalid RX DMA size\n");
+			return NULL;
+		}
+	}
+
+	dma_async_tx_descriptor_init(&ud->tx, &uc->chan);
+	ud->tx.tx_submit = ast2600_udma_tx_submit;
+
+	return &ud->tx;
+}
+
+static void ast2600_udma_issue_pending(struct dma_chan *chan)
+{
+	unsigned long flags;
+	uint32_t r_pr, r_is, r_ie, r_en, reg;
+	uint32_t ch_id = chan->chan_id;
+	uint32_t ch_bit = ch_id / 2;
+	dma_addr_t rx_addr;
+	uint32_t rx_size;
+	struct ast2600_udma_chan *uc = to_ast2600_udma_chan(chan);
+	struct ast2600_udma_desc *ud = &uc->ud;
+	struct ast2600_udma *udma = uc->udma;
+
+	if (uc->is_tx) {
+		r_pr = UDMA_TX_PTR_RST;
+		r_is = UDMA_TX_INT_STS;
+		r_ie = UDMA_TX_INT_EN;
+		r_en = UDMA_TX_EN;
+	} else {
+		r_pr = UDMA_RX_PTR_RST;
+		r_is = UDMA_RX_INT_STS;
+		r_ie = UDMA_RX_INT_EN;
+		r_en = UDMA_RX_EN;
+	}
+
+	spin_lock_irqsave(&udma->lock, flags);
+
+	/* reset channel HW read/write pointer */
+	writel(BIT(ch_bit), udma->regs + r_pr);
+	writel(0, udma->regs + r_pr);
+
+	/* clear interrupt status */
+	writel(BIT(ch_bit), udma->regs + r_is);
+
+	/* set transfer address & size */
+	if (uc->is_tx) {
+		writel(ud->addr, udma->regs + UDMA_CH_ADDR(ch_id));
+		writel(ud->size, udma->regs + UDMA_CH_WPTR(ch_id));
+		writel(UDMA_BUFSZ_64KB, udma->regs + UDMA_CH_CTRL(ch_id));
+	} else {
+		/*
+		 * UDMA is limited to 4B-aligned addresses.
+		 * Thus use local 4B-aligned buffer to get
+		 * RX data and copy to the real destination
+		 * after then.
+		 */
+		rx_addr = (ud->addr & 0x3) ? uc->buf_addr : ud->addr;
+		rx_size = FIELD_GET(UDMA_CH_CTRL_BUFSZ, ud->size);
+		writel(rx_addr, udma->regs + UDMA_CH_ADDR(ch_id));
+		writel(rx_size, udma->regs + UDMA_CH_CTRL(ch_id));
+	}
+
+	/* enable interrupt */
+	reg = readl(udma->regs + r_ie) | BIT(ch_bit);
+	writel(reg, udma->regs + r_ie);
+
+	/* start DMA */
+	reg = readl(udma->regs + r_en) | BIT(ch_bit);
+	writel(reg, udma->regs + r_en);
+
+	spin_unlock_irqrestore(&udma->lock, flags);
+}
+
+static enum dma_status ast2600_udma_tx_status(struct dma_chan *chan,
+		dma_cookie_t cookie, struct dma_tx_state *txstate)
+{
+	struct ast2600_udma_chan *uc = to_ast2600_udma_chan(chan);
+	enum dma_status sts = dma_cookie_status(chan, cookie, txstate);
+
+	dma_set_residue(txstate, uc->residue);
+
+	return sts;
+}
+
+static int ast2600_udma_pause(struct dma_chan *chan)
+{
+	unsigned long flags;
+	uint32_t r_en, r_ie, reg;
+	uint32_t ch_id = chan->chan_id;
+	uint32_t ch_bit = ch_id / 2;
+	struct ast2600_udma_chan *uc = to_ast2600_udma_chan(chan);
+	struct ast2600_udma *udma = uc->udma;
+
+	if (uc->is_tx) {
+		r_en = UDMA_TX_EN;
+		r_ie = UDMA_TX_INT_EN;
+	} else {
+		r_en = UDMA_RX_EN;
+		r_ie = UDMA_RX_INT_EN;
+	}
+
+	spin_lock_irqsave(&udma->lock, flags);
+
+	reg = readl(udma->regs + r_en) & ~BIT(ch_bit);
+	writel(reg, udma->regs + r_en);
+
+	reg = readl(udma->regs + r_ie) & ~BIT(ch_bit);
+	writel(reg, udma->regs + r_ie);
+
+	spin_unlock_irqrestore(&udma->lock, flags);
+
+	return 0;
+}
+
+static int ast2600_udma_resume(struct dma_chan *chan)
+{
+	unsigned long flags;
+	uint32_t r_en, r_ie, reg;
+	uint32_t ch_id = chan->chan_id;
+	uint32_t ch_bit = ch_id / 2;
+	struct ast2600_udma_chan *uc = to_ast2600_udma_chan(chan);
+	struct ast2600_udma *udma = uc->udma;
+
+	if (uc->is_tx) {
+		r_en = UDMA_TX_EN;
+		r_ie = UDMA_TX_INT_EN;
+	} else {
+		r_en = UDMA_RX_EN;
+		r_ie = UDMA_RX_INT_EN;
+	}
+
+	spin_lock_irqsave(&udma->lock, flags);
+
+	reg = readl(udma->regs + r_en) | BIT(ch_bit);
+	writel(reg, udma->regs + r_en);
+
+	reg = readl(udma->regs + r_ie) | BIT(ch_bit);
+	writel(reg, udma->regs + r_ie);
+
+	spin_unlock_irqrestore(&udma->lock, flags);
+
+	return 0;
+}
+
+static int ast2600_udma_terminate(struct dma_chan *chan)
+{
+	unsigned long flags;
+	uint32_t r_pr, r_is, r_ie, r_en, reg;
+	uint32_t ch_id = chan->chan_id;
+	uint32_t ch_bit = ch_id / 2;
+	struct ast2600_udma_chan *uc = to_ast2600_udma_chan(chan);
+	struct ast2600_udma *udma = uc->udma;
+
+	if (uc->is_tx) {
+		r_pr = UDMA_TX_PTR_RST;
+		r_is = UDMA_TX_INT_STS;
+		r_ie = UDMA_TX_INT_EN;
+		r_en = UDMA_TX_EN;
+	} else {
+		r_pr = UDMA_RX_PTR_RST;
+		r_is = UDMA_RX_INT_STS;
+		r_ie = UDMA_RX_INT_EN;
+		r_en = UDMA_RX_EN;
+	}
+
+	spin_lock_irqsave(&udma->lock, flags);
+
+	/* disable DMA */
+	reg = readl(udma->regs + r_en) & ~BIT(ch_bit);
+	writel(reg, udma->regs + r_en);
+
+	/* disable interrupt */
+	reg = readl(udma->regs + r_ie) & ~BIT(ch_bit);
+	writel(reg, udma->regs + r_ie);
+
+	/* clear interrupt status */
+	writel(BIT(ch_bit), udma->regs + r_is);
+
+	/* reset channel HW read/write pointer */
+	writel(BIT(ch_bit), udma->regs + r_pr);
+	writel(0, udma->regs + r_pr);
+
+	spin_unlock_irqrestore(&udma->lock, flags);
+
+	return 0;
+}
+
+static irqreturn_t ast2600_udma_isr(int irq, void *arg)
+{
+	struct ast2600_udma *udma = arg;
+	struct ast2600_udma_chan *uc;
+	struct ast2600_udma_desc *ud;
+	struct dma_async_tx_descriptor *tx;
+	uint32_t sts, rptr, wptr;
+	uint32_t ch_id, ch_bit;
+	void *p;
+
+	/* handle TX interrupt */
+	sts = readl(udma->regs + UDMA_TX_INT_STS);
+	for_each_set_bit(ch_bit, (unsigned long *)&sts, (udma->n_ucs / 2)) {
+		ch_id = ch_bit << 1;
+		rptr = readl(udma->regs + UDMA_CH_RPTR(ch_id));
+		wptr = readl(udma->regs + UDMA_CH_WPTR(ch_id));
+
+		uc = &udma->ucs[ch_id];
+		uc->residue = wptr - rptr;
+
+		ast2600_udma_terminate(&uc->chan);
+
+		tx = &uc->ud.tx;
+		dma_cookie_complete(tx);
+		dma_descriptor_unmap(tx);
+		dmaengine_desc_get_callback_invoke(tx, NULL);
+	}
+
+	/* handle RX interrupt */
+	sts = readl(udma->regs + UDMA_RX_INT_STS);
+	for_each_set_bit(ch_bit, (unsigned long *)&sts, udma->n_ucs / 2) {
+		ch_id = (ch_bit << 1) + 1;
+		wptr = readl(udma->regs + UDMA_CH_WPTR(ch_id));
+
+		uc = &udma->ucs[ch_id];
+		ud = &uc->ud;
+		tx = &ud->tx;
+
+		uc->residue = (ud->size & ~UDMA_CH_CTRL_BUFSZ) - wptr;
+
+		/* handle non-4B-aligned case */
+		if (ud->addr & 0x3) {
+			p = phys_to_virt(dma_to_phys(uc->chan.device->dev, ud->addr));
+			memcpy(p, uc->buf, wptr);
+		}
+
+		ast2600_udma_terminate(&uc->chan);
+
+		dma_cookie_complete(tx);
+		dma_descriptor_unmap(tx);
+		dmaengine_desc_get_callback_invoke(tx, NULL);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int ast2600_udma_probe(struct platform_device *pdev)
+{
+	int i, rc;
+	struct resource *res;
+	struct ast2600_udma *udma;
+	struct device *dev = &pdev->dev;
+
+	udma = devm_kzalloc(dev, sizeof(*udma), GFP_KERNEL);
+	if (!udma)
+		return -ENOMEM;
+
+	dma_cap_set(DMA_SLAVE, udma->ddev.cap_mask);
+	udma->ddev.device_alloc_chan_resources = ast2600_udma_alloc_chan_resources;
+	udma->ddev.device_prep_slave_sg = ast2600_udma_prep_slave_sg;
+	udma->ddev.device_issue_pending = ast2600_udma_issue_pending;
+	udma->ddev.device_tx_status = ast2600_udma_tx_status;
+	udma->ddev.device_pause = ast2600_udma_pause;
+	udma->ddev.device_resume = ast2600_udma_resume;
+	udma->ddev.device_terminate_all = ast2600_udma_terminate;
+	udma->ddev.src_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE);
+	udma->ddev.dst_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE);
+	udma->ddev.directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);
+	udma->ddev.residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;
+	udma->ddev.dev = dev;
+	INIT_LIST_HEAD(&udma->ddev.channels);
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (IS_ERR(res)) {
+		dev_err(dev, "cannot get IO resource\n");
+		return -ENODEV;
+	}
+
+	udma->regs = devm_ioremap_resource(dev, res);
+	if (IS_ERR(udma->regs)) {
+		dev_err(dev, "cannot map IO registers\n");
+		return PTR_ERR(udma->regs);
+	}
+
+	/* timeout value: 0x200 * (PCLK * 14400) */
+	writel(0x200, udma->regs + UDMA_TMOUT);
+
+	/* disable all for safety */
+	writel(0x0, udma->regs + UDMA_TX_EN);
+	writel(0x0, udma->regs + UDMA_RX_EN);
+
+	udma->irq = platform_get_irq(pdev, 0);
+	if (udma->irq < 0)
+		return udma->irq;
+
+	rc = devm_request_irq(&pdev->dev, udma->irq, ast2600_udma_isr,
+			      IRQF_SHARED, DEVICE_NAME, udma);
+	if (rc) {
+		dev_err(dev, "cannot request IRQ\n");
+		return rc;
+	}
+
+	rc = of_property_read_u32(dev->of_node, "dma-channels", &udma->n_ucs);
+	if (rc) {
+		dev_err(dev, "cannot find number of channels\n");
+		return rc;
+	}
+
+	udma->ucs = devm_kzalloc(dev,
+				 sizeof(struct ast2600_udma_chan) * udma->n_ucs, GFP_KERNEL);
+	if (!udma->ucs)
+		return -ENOMEM;
+
+	for (i = 0; i < udma->n_ucs; ++i) {
+		udma->ucs[i].is_tx = !(i % 2);
+		udma->ucs[i].chan.device = &udma->ddev;
+		udma->ucs[i].buf = dmam_alloc_coherent(dev, UDMA_MAX_BUFSZ,
+						       &udma->ucs[i].buf_addr, GFP_KERNEL);
+		if (!udma->ucs[i].buf)
+			return -ENOMEM;
+
+		udma->ucs[i].udma = udma;
+		list_add_tail(&udma->ucs[i].chan.device_node, &udma->ddev.channels);
+	}
+
+	rc = dma_async_device_register(&udma->ddev);
+	if (rc)
+		return rc;
+
+	rc = of_dma_controller_register(dev->of_node, of_dma_xlate_by_chan_id, &udma->ddev);
+	if (rc)
+		return rc;
+
+	spin_lock_init(&udma->lock);
+
+	platform_set_drvdata(pdev, udma);
+
+	dev_info(dev, "module loaded\n");
+
+	return 0;
+}
+
+static int ast2600_udma_remove(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct ast2600_udma *udma = platform_get_drvdata(pdev);
+
+	of_dma_controller_free(dev->of_node);
+	dma_async_device_unregister(&udma->ddev);
+
+	dev_info(dev, "module removed\n");
+
+	return 0;
+}
+
+static const struct of_device_id ast2600_udma_match[] = {
+	{ .compatible = "aspeed,ast2600-udma" },
+	{ },
+};
+
+static struct platform_driver ast2600_udma_driver = {
+	.probe = ast2600_udma_probe,
+	.remove = ast2600_udma_remove,
+	.driver = {
+			.name = DEVICE_NAME,
+			.of_match_table = ast2600_udma_match,
+	},
+};
+
+module_platform_driver(ast2600_udma_driver);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Chia-Wei Wang <chiawei_wang@xxxxxxxxxxxxxx");
-- 
2.25.1