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, 6 insertions, 19 deletions

diff --git a/drivers/tty/serial/icom.c b/drivers/tty/serial/icom.c
index a75eafbcbea3..29e42831df39 100644
--- a/drivers/tty/serial/icom.c
+++ b/drivers/tty/serial/icom.c
@@ -877,10 +877,10 @@ unlock:
 static int icom_write(struct uart_port *port)
 {
 	struct icom_port *icom_port = to_icom_port(port);
+	struct tty_port *tport = &port->state->port;
 	unsigned long data_count;
 	unsigned char cmdReg;
 	unsigned long offset;
-	int temp_tail = port->state->xmit.tail;
 
 	trace(icom_port, "WRITE", 0);
 
@@ -890,16 +890,8 @@ static int icom_write(struct uart_port *port)
 		return 0;
 	}
 
-	data_count = 0;
-	while ((port->state->xmit.head != temp_tail) &&
-	       (data_count <= XMIT_BUFF_SZ)) {
-
-		icom_port->xmit_buf[data_count++] =
-		    port->state->xmit.buf[temp_tail];
-
-		temp_tail++;
-		temp_tail &= (UART_XMIT_SIZE - 1);
-	}
+	data_count = kfifo_out_peek(&tport->xmit_fifo, icom_port->xmit_buf,
+			XMIT_BUFF_SZ);
 
 	if (data_count) {
 		icom_port->statStg->xmit[0].flags =
@@ -956,7 +948,8 @@ static inline void check_modem_status(struct icom_port *icom_port)
 
 static void xmit_interrupt(u16 port_int_reg, struct icom_port *icom_port)
 {
-	u16 count, i;
+	struct tty_port *tport = &icom_port->uart_port.state->port;
+	u16 count;
 
 	if (port_int_reg & (INT_XMIT_COMPLETED)) {
 		trace(icom_port, "XMIT_COMPLETE", 0);
@@ -968,13 +961,7 @@ static void xmit_interrupt(u16 port_int_reg, struct icom_port *icom_port)
 		count = le16_to_cpu(icom_port->statStg->xmit[0].leLength);
 		icom_port->uart_port.icount.tx += count;
 
-		for (i=0; i<count &&
-			!uart_circ_empty(&icom_port->uart_port.state->xmit); i++) {
-
-			icom_port->uart_port.state->xmit.tail++;
-			icom_port->uart_port.state->xmit.tail &=
-				(UART_XMIT_SIZE - 1);
-		}
+		kfifo_skip_count(&tport->xmit_fifo, count);
 
 		if (!icom_write(&icom_port->uart_port))
 			/* activate write queue */