Re: [PATCH] serial: msm: Unify TX and RX DMA paths

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Hi Marek,

On 23/04/2024 14:08, Marek Szyprowski wrote:

Use scatterlist-based API also for RX mode to unify TX and RX DMA paths
as well as simplify the whole driver code a bit.


Thanks for the patch, I have no idea if this is right or wrong.

Greg, I think we should wait until this change is fully tested on multiple
platforms including DMA usage (bluetooth) before aplying it.

Thanks,
Neil



Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
---
  drivers/tty/serial/msm_serial.c | 86 +++++++++++++--------------------
  1 file changed, 34 insertions(+), 52 deletions(-)

diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c
index 0a9c5219df88..d5e00e613f73 100644
--- a/drivers/tty/serial/msm_serial.c
+++ b/drivers/tty/serial/msm_serial.c
@@ -161,14 +161,8 @@ enum {
  struct msm_dma {
  	struct dma_chan		*chan;
  	enum dma_data_direction dir;
-	union {
-		struct {
-			dma_addr_t		phys;
-			unsigned char		*virt;
-			unsigned int		count;
-		} rx;
-		struct scatterlist tx_sg;
-	};
+	unsigned char		*virt;
+	struct scatterlist	sg;
  	dma_cookie_t		cookie;
  	u32			enable_bit;
  	struct dma_async_tx_descriptor	*desc;
@@ -254,13 +248,7 @@ static void msm_stop_dma(struct uart_port *port, struct msm_dma *dma)
  	unsigned int mapped;
  	u32 val;
- if (dma->dir == DMA_TO_DEVICE) { 
-		mapped = sg_dma_len(&dma->tx_sg);
-	} else {
-		mapped = dma->rx.count;
-		dma->rx.count = 0;
-	}
-
+	mapped = sg_dma_len(&dma->sg);
  	dmaengine_terminate_all(dma->chan);
/* 
@@ -275,11 +263,8 @@ static void msm_stop_dma(struct uart_port *port, struct msm_dma *dma)
  	msm_write(port, val, UARTDM_DMEN);
if (mapped) { 
-		if (dma->dir == DMA_TO_DEVICE) {
-			dma_unmap_sg(dev, &dma->tx_sg, 1, dma->dir);
-			sg_init_table(&dma->tx_sg, 1);
-		} else
-			dma_unmap_single(dev, dma->rx.phys, mapped, dma->dir);
+		dma_unmap_sg(dev, &dma->sg, 1, dma->dir);
+		sg_init_table(&dma->sg, 1);
  	}
  }
@@ -299,7 +284,7 @@ static void msm_release_dma(struct msm_port *msm_port) 
  	if (dma->chan) {
  		msm_stop_dma(&msm_port->uart, dma);
  		dma_release_channel(dma->chan);
-		kfree(dma->rx.virt);
+		kfree(dma->virt);
  	}
memset(dma, 0, sizeof(*dma)); 
@@ -371,8 +356,8 @@ static void msm_request_rx_dma(struct msm_port *msm_port, resource_size_t base)
of_property_read_u32(dev->of_node, "qcom,rx-crci", &crci); - dma->rx.virt = kzalloc(UARTDM_RX_SIZE, GFP_KERNEL); 
-	if (!dma->rx.virt)
+	dma->virt = kzalloc(UARTDM_RX_SIZE, GFP_KERNEL);
+	if (!dma->virt)
  		goto rel_rx;
memset(&conf, 0, sizeof(conf)); 
@@ -399,7 +384,7 @@ static void msm_request_rx_dma(struct msm_port *msm_port, resource_size_t base)
return; 
  err:
-	kfree(dma->rx.virt);
+	kfree(dma->virt);
  rel_rx:
  	dma_release_channel(dma->chan);
  no_rx:
@@ -434,7 +419,7 @@ static void msm_start_tx(struct uart_port *port)
  	struct msm_dma *dma = &msm_port->tx_dma;
/* Already started in DMA mode */ 
-	if (sg_dma_len(&dma->tx_sg))
+	if (sg_dma_len(&dma->sg))
  		return;
msm_port->imr |= MSM_UART_IMR_TXLEV; 
@@ -462,12 +447,12 @@ static void msm_complete_tx_dma(void *args)
  	uart_port_lock_irqsave(port, &flags);
/* Already stopped */ 
-	if (!sg_dma_len(&dma->tx_sg))
+	if (!sg_dma_len(&dma->sg))
  		goto done;
dmaengine_tx_status(dma->chan, dma->cookie, &state); - dma_unmap_sg(port->dev, &dma->tx_sg, 1, dma->dir); 
+	dma_unmap_sg(port->dev, &dma->sg, 1, dma->dir);
val = msm_read(port, UARTDM_DMEN); 
  	val &= ~dma->enable_bit;
@@ -478,9 +463,9 @@ static void msm_complete_tx_dma(void *args)
  		msm_write(port, MSM_UART_CR_TX_ENABLE, MSM_UART_CR);
  	}
- count = sg_dma_len(&dma->tx_sg) - state.residue; 
+	count = sg_dma_len(&dma->sg) - state.residue;
  	uart_xmit_advance(port, count);
-	sg_init_table(&dma->tx_sg, 1);
+	sg_init_table(&dma->sg, 1);
/* Restore "Tx FIFO below watermark" interrupt */ 
  	msm_port->imr |= MSM_UART_IMR_TXLEV;
@@ -503,16 +488,16 @@ static int msm_handle_tx_dma(struct msm_port *msm_port, unsigned int count)
  	int ret;
  	u32 val;
- sg_init_table(&dma->tx_sg, 1); 
-	kfifo_dma_out_prepare(&tport->xmit_fifo, &dma->tx_sg, 1, count);
+	sg_init_table(&dma->sg, 1);
+	kfifo_dma_out_prepare(&tport->xmit_fifo, &dma->sg, 1, count);
- mapped = dma_map_sg(port->dev, &dma->tx_sg, 1, dma->dir); 
+	mapped = dma_map_sg(port->dev, &dma->sg, 1, dma->dir);
  	if (!mapped) {
  		ret = -EIO;
  		goto zero_sg;
  	}
- dma->desc = dmaengine_prep_slave_sg(dma->chan, &dma->tx_sg, 1, 
+	dma->desc = dmaengine_prep_slave_sg(dma->chan, &dma->sg, 1,
  						DMA_MEM_TO_DEV,
  						DMA_PREP_INTERRUPT |
  						DMA_PREP_FENCE);
@@ -550,9 +535,9 @@ static int msm_handle_tx_dma(struct msm_port *msm_port, unsigned int count)
  	dma_async_issue_pending(dma->chan);
  	return 0;
  unmap:
-	dma_unmap_sg(port->dev, &dma->tx_sg, 1, dma->dir);
+	dma_unmap_sg(port->dev, &dma->sg, 1, dma->dir);
  zero_sg:
-	sg_init_table(&dma->tx_sg, 1);
+	sg_init_table(&dma->sg, 1);
  	return ret;
  }
@@ -569,7 +554,7 @@ static void msm_complete_rx_dma(void *args) 
  	uart_port_lock_irqsave(port, &flags);
/* Already stopped */ 
-	if (!dma->rx.count)
+	if (!sg_dma_len(&dma->sg))
  		goto done;
val = msm_read(port, UARTDM_DMEN); 
@@ -586,14 +571,13 @@ static void msm_complete_rx_dma(void *args)
port->icount.rx += count; - dma->rx.count = 0; 
-
-	dma_unmap_single(port->dev, dma->rx.phys, UARTDM_RX_SIZE, dma->dir);
+	dma_unmap_sg(port->dev, &dma->sg, 1, dma->dir);
+	sg_init_table(&dma->sg, 1);
for (i = 0; i < count; i++) { 
  		char flag = TTY_NORMAL;
- if (msm_port->break_detected && dma->rx.virt[i] == 0) { 
+		if (msm_port->break_detected && dma->virt[i] == 0) {
  			port->icount.brk++;
  			flag = TTY_BREAK;
  			msm_port->break_detected = false;
@@ -604,9 +588,9 @@ static void msm_complete_rx_dma(void *args)
  		if (!(port->read_status_mask & MSM_UART_SR_RX_BREAK))
  			flag = TTY_NORMAL;
- sysrq = uart_prepare_sysrq_char(port, dma->rx.virt[i]); 
+		sysrq = uart_prepare_sysrq_char(port, dma->virt[i]);
  		if (!sysrq)
-			tty_insert_flip_char(tport, dma->rx.virt[i], flag);
+			tty_insert_flip_char(tport, dma->virt[i], flag);
  	}
msm_start_rx_dma(msm_port); 
@@ -630,14 +614,13 @@ static void msm_start_rx_dma(struct msm_port *msm_port)
  	if (!dma->chan)
  		return;
- dma->rx.phys = dma_map_single(uart->dev, dma->rx.virt, 
-				   UARTDM_RX_SIZE, dma->dir);
-	ret = dma_mapping_error(uart->dev, dma->rx.phys);
-	if (ret)
+	sg_init_one(&dma->sg, dma->virt, UARTDM_RX_SIZE);
+	ret = dma_map_sg(uart->dev, &dma->sg, 1, dma->dir);
+	if (!ret)
  		goto sw_mode;
- dma->desc = dmaengine_prep_slave_single(dma->chan, dma->rx.phys, 
-						UARTDM_RX_SIZE, DMA_DEV_TO_MEM,
+	dma->desc = dmaengine_prep_slave_sg(dma->chan, &dma->sg, 1,
+						DMA_DEV_TO_MEM,
  						DMA_PREP_INTERRUPT);
  	if (!dma->desc)
  		goto unmap;
@@ -664,8 +647,6 @@ static void msm_start_rx_dma(struct msm_port *msm_port)
msm_write(uart, msm_port->imr, MSM_UART_IMR); - dma->rx.count = UARTDM_RX_SIZE; 
-
  	dma_async_issue_pending(dma->chan);
msm_write(uart, MSM_UART_CR_CMD_RESET_STALE_INT, MSM_UART_CR); 
@@ -684,7 +665,8 @@ static void msm_start_rx_dma(struct msm_port *msm_port)
return; 
  unmap:
-	dma_unmap_single(uart->dev, dma->rx.phys, UARTDM_RX_SIZE, dma->dir);
+	dma_unmap_sg(uart->dev, &dma->sg, 1, dma->dir);
+	sg_init_table(&dma->sg, 1);
sw_mode: 
  	/*
@@ -967,7 +949,7 @@ static irqreturn_t msm_uart_irq(int irq, void *dev_id)
  	}
if (misr & (MSM_UART_IMR_RXLEV | MSM_UART_IMR_RXSTALE)) { 
-		if (dma->rx.count) {
+		if (sg_dma_len(&dma->sg)) {
  			val = MSM_UART_CR_CMD_STALE_EVENT_DISABLE;
  			msm_write(port, val, MSM_UART_CR);
  			val = MSM_UART_CR_CMD_RESET_STALE_INT;
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