tty: serial: switch from circ_buf to kfifo

Switch from struct circ_buf to proper kfifo. kfifo provides much better
API, esp. when wrap-around of the buffer needs to be taken into account.
Look at pl011_dma_tx_refill() or cpm_uart_tx_pump() changes for example.

Kfifo API can also fill in scatter-gather DMA structures, so it easier
for that use case too. Look at lpuart_dma_tx() for example. Note that
not all drivers can be converted to that (like atmel_serial), they
handle DMA specially.

Note that usb-serial uses kfifo for TX for ages.

omap needed a bit more care as it needs to put a char into FIFO to start
the DMA transfer when OMAP_DMA_TX_KICK is set. In that case, we have to
do kfifo_dma_out_prepare twice: once to find out the tx_size (to find
out if it is worths to do DMA at all -- size >= 4), the second time for
the actual transfer.

All traces of circ_buf are removed from serial_core.h (and its struct
uart_state).

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Cc: Al Cooper <alcooperx@gmail.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Cc: Kumaravel Thiagarajan <kumaravel.thiagarajan@microchip.com>
Cc: Tharun Kumar P <tharunkumar.pasumarthi@microchip.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Vineet Gupta <vgupta@kernel.org>
Cc: Richard Genoud <richard.genoud@gmail.com>
Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Claudiu Beznea <claudiu.beznea@tuxon.dev>
Cc: Alexander Shiyan <shc_work@mail.ru>
Cc: Baruch Siach <baruch@tkos.co.il>
Cc: Maciej W. Rozycki <macro@orcam.me.uk>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: Neil Armstrong <neil.armstrong@linaro.org>
Cc: Kevin Hilman <khilman@baylibre.com>
Cc: Jerome Brunet <jbrunet@baylibre.com>
Cc: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Cc: Taichi Sugaya <sugaya.taichi@socionext.com>
Cc: Takao Orito <orito.takao@socionext.com>
Cc: Bjorn Andersson <andersson@kernel.org>
Cc: Konrad Dybcio <konrad.dybcio@linaro.org>
Cc: Pali Rohár <pali@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Aneesh Kumar K.V <aneesh.kumar@kernel.org>
Cc: Naveen N. Rao <naveen.n.rao@linux.ibm.com>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc: Alim Akhtar <alim.akhtar@samsung.com>
Cc: Laxman Dewangan <ldewangan@nvidia.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Jonathan Hunter <jonathanh@nvidia.com>
Cc: Orson Zhai <orsonzhai@gmail.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Chunyan Zhang <zhang.lyra@gmail.com>
Cc: Patrice Chotard <patrice.chotard@foss.st.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Hammer Hsieh <hammerh0314@gmail.com>
Cc: Peter Korsgaard <jacmet@sunsite.dk>
Cc: Timur Tabi <timur@kernel.org>
Cc: Michal Simek <michal.simek@amd.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Christian König <christian.koenig@amd.com>
Link: https://lore.kernel.org/r/20240405060826.2521-13-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 28 insertions, 26 deletions

diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
index a2d07e05c502..dc35eb77d2ef 100644
--- a/drivers/tty/serial/samsung_tty.c
+++ b/drivers/tty/serial/samsung_tty.c
@@ -329,7 +329,7 @@ static void s3c24xx_serial_tx_dma_complete(void *args)
 {
 	struct s3c24xx_uart_port *ourport = args;
 	struct uart_port *port = &ourport->port;
-	struct circ_buf *xmit = &port->state->xmit;
+	struct tty_port *tport = &port->state->port;
 	struct s3c24xx_uart_dma *dma = ourport->dma;
 	struct dma_tx_state state;
 	unsigned long flags;
@@ -348,7 +348,7 @@ static void s3c24xx_serial_tx_dma_complete(void *args)
 	uart_xmit_advance(port, count);
 	ourport->tx_in_progress = 0;
 
-	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+	if (kfifo_len(&tport->xmit_fifo) < WAKEUP_CHARS)
 		uart_write_wakeup(port);
 
 	s3c24xx_serial_start_next_tx(ourport);
@@ -431,17 +431,15 @@ static void s3c24xx_serial_start_tx_pio(struct s3c24xx_uart_port *ourport)
 }
 
 static int s3c24xx_serial_start_tx_dma(struct s3c24xx_uart_port *ourport,
-				      unsigned int count)
+				      unsigned int count, unsigned int tail)
 {
-	struct uart_port *port = &ourport->port;
-	struct circ_buf *xmit = &port->state->xmit;
 	struct s3c24xx_uart_dma *dma = ourport->dma;
 
 	if (ourport->tx_mode != S3C24XX_TX_DMA)
 		enable_tx_dma(ourport);
 
 	dma->tx_size = count & ~(dma_get_cache_alignment() - 1);
-	dma->tx_transfer_addr = dma->tx_addr + xmit->tail;
+	dma->tx_transfer_addr = dma->tx_addr + tail;
 
 	dma_sync_single_for_device(dma->tx_chan->device->dev,
 				   dma->tx_transfer_addr, dma->tx_size,
@@ -468,11 +466,11 @@ static int s3c24xx_serial_start_tx_dma(struct s3c24xx_uart_port *ourport,
 static void s3c24xx_serial_start_next_tx(struct s3c24xx_uart_port *ourport)
 {
 	struct uart_port *port = &ourport->port;
-	struct circ_buf *xmit = &port->state->xmit;
-	unsigned long count;
+	struct tty_port *tport = &port->state->port;
+	unsigned int count, tail;
 
 	/* Get data size up to the end of buffer */
-	count = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
+	count = kfifo_out_linear(&tport->xmit_fifo, &tail, UART_XMIT_SIZE);
 
 	if (!count) {
 		s3c24xx_serial_stop_tx(port);
@@ -481,16 +479,16 @@ static void s3c24xx_serial_start_next_tx(struct s3c24xx_uart_port *ourport)
 
 	if (!ourport->dma || !ourport->dma->tx_chan ||
 	    count < ourport->min_dma_size ||
-	    xmit->tail & (dma_get_cache_alignment() - 1))
+	    tail & (dma_get_cache_alignment() - 1))
 		s3c24xx_serial_start_tx_pio(ourport);
 	else
-		s3c24xx_serial_start_tx_dma(ourport, count);
+		s3c24xx_serial_start_tx_dma(ourport, count, tail);
 }
 
 static void s3c24xx_serial_start_tx(struct uart_port *port)
 {
 	struct s3c24xx_uart_port *ourport = to_ourport(port);
-	struct circ_buf *xmit = &port->state->xmit;
+	struct tty_port *tport = &port->state->port;
 
 	if (!ourport->tx_enabled) {
 		if (port->flags & UPF_CONS_FLOW)
@@ -502,7 +500,8 @@ static void s3c24xx_serial_start_tx(struct uart_port *port)
 	}
 
 	if (ourport->dma && ourport->dma->tx_chan) {
-		if (!uart_circ_empty(xmit) && !ourport->tx_in_progress)
+		if (!kfifo_is_empty(&tport->xmit_fifo) &&
+				!ourport->tx_in_progress)
 			s3c24xx_serial_start_next_tx(ourport);
 	}
 }
@@ -868,18 +867,19 @@ static irqreturn_t s3c24xx_serial_rx_irq(int irq, void *dev_id)
 static void s3c24xx_serial_tx_chars(struct s3c24xx_uart_port *ourport)
 {
 	struct uart_port *port = &ourport->port;
-	struct circ_buf *xmit = &port->state->xmit;
-	int count, dma_count = 0;
+	struct tty_port *tport = &port->state->port;
+	unsigned int count, dma_count = 0, tail;
 
-	count = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
+	count = kfifo_out_linear(&tport->xmit_fifo, &tail, UART_XMIT_SIZE);
 
 	if (ourport->dma && ourport->dma->tx_chan &&
 	    count >= ourport->min_dma_size) {
 		int align = dma_get_cache_alignment() -
-			(xmit->tail & (dma_get_cache_alignment() - 1));
+			(tail & (dma_get_cache_alignment() - 1));
 		if (count - align >= ourport->min_dma_size) {
 			dma_count = count - align;
 			count = align;
+			tail += align;
 		}
 	}
 
@@ -894,7 +894,7 @@ static void s3c24xx_serial_tx_chars(struct s3c24xx_uart_port *ourport)
 	 * stopped, disable the uart and exit
 	 */
 
-	if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
+	if (kfifo_is_empty(&tport->xmit_fifo) || uart_tx_stopped(port)) {
 		s3c24xx_serial_stop_tx(port);
 		return;
 	}
@@ -906,24 +906,25 @@ static void s3c24xx_serial_tx_chars(struct s3c24xx_uart_port *ourport)
 		dma_count = 0;
 	}
 
-	while (!uart_circ_empty(xmit) && count > 0) {
-		if (rd_regl(port, S3C2410_UFSTAT) & ourport->info->tx_fifofull)
+	while (!(rd_regl(port, S3C2410_UFSTAT) & ourport->info->tx_fifofull)) {
+		unsigned char ch;
+
+		if (!uart_fifo_get(port, &ch))
 			break;
 
-		wr_reg(port, S3C2410_UTXH, xmit->buf[xmit->tail]);
-		uart_xmit_advance(port, 1);
+		wr_reg(port, S3C2410_UTXH, ch);
 		count--;
 	}
 
 	if (!count && dma_count) {
-		s3c24xx_serial_start_tx_dma(ourport, dma_count);
+		s3c24xx_serial_start_tx_dma(ourport, dma_count, tail);
 		return;
 	}
 
-	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+	if (kfifo_len(&tport->xmit_fifo) < WAKEUP_CHARS)
 		uart_write_wakeup(port);
 
-	if (uart_circ_empty(xmit))
+	if (kfifo_is_empty(&tport->xmit_fifo))
 		s3c24xx_serial_stop_tx(port);
 }
 
@@ -1118,7 +1119,8 @@ static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p)
 
 	/* TX buffer */
 	dma->tx_addr = dma_map_single(dma->tx_chan->device->dev,
-				      p->port.state->xmit.buf, UART_XMIT_SIZE,
+				      p->port.state->port.xmit_buf,
+				      UART_XMIT_SIZE,
 				      DMA_TO_DEVICE);
 	if (dma_mapping_error(dma->tx_chan->device->dev, dma->tx_addr)) {
 		reason = "DMA mapping error for TX buffer";