Revert "serial: ns16550: Add RX interrupt buffer support"

This reverts commit 6822cf3ec7.

As Bin Meng has tested and pointed out, we don't need the RX interrupt
for the RX buffer support at all. Just reading all available characters
into a buffer is sufficient to solve the problem with the dropped
characters upon long lines pasted into the U-Boot prompt. Since this
RX buffer support can be implemented in a generic way, without any
device specifica (e.g. for the ns16550), I'll post a new patch with
a new serial RX buffer support for DM, which all DM based serial
drivers can use.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Simon Glass <sjg@chromium.org>
Cc: Bin Meng <bmeng.cn@gmail.com>
Cc: Tom Rini <trini@konsulko.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

drivers/serial/Kconfig

@@ -64,16 +64,6 @@ config DM_SERIAL
 	  implements serial_putc() etc. The uclass interface is
 	  defined in include/serial.h.
 
-config SERIAL_IRQ_BUFFER
-	bool "Enable RX interrupt buffer for serial input"
-	depends on DM_SERIAL
-	default n
-	help
-	  Enable RX interrupt buffer support for the serial driver.
-	  This enables pasting longer strings, even when the RX FIFO
-	  of the UART is not big enough (e.g. 16 bytes on the normal
-	  NS16550).
-
 config SPL_DM_SERIAL
 	bool "Enable Driver Model for serial drivers in SPL"
 	depends on DM_SERIAL

drivers/serial/ns16550.c

@@ -314,80 +314,6 @@ DEBUG_UART_FUNCS
 #endif
 
 #ifdef CONFIG_DM_SERIAL
-
-#if CONFIG_IS_ENABLED(SERIAL_IRQ_BUFFER)
-
-#define BUF_COUNT	256
-
-static void rx_fifo_to_buf(struct udevice *dev)
-{
-	struct NS16550 *const com_port = dev_get_priv(dev);
-	struct ns16550_platdata *plat = dev->platdata;
-
-	/* Read all available chars into buffer */
-	while ((serial_in(&com_port->lsr) & UART_LSR_DR)) {
-		plat->buf[plat->wr_ptr++] = serial_in(&com_port->rbr);
-		plat->wr_ptr %= BUF_COUNT;
-	}
-}
-
-static int rx_pending(struct udevice *dev)
-{
-	struct ns16550_platdata *plat = dev->platdata;
-
-	/*
-	 * At startup it may happen, that some already received chars are
-	 * "stuck" in the RX FIFO, even with the interrupt enabled. This
-	 * RX FIFO flushing makes sure, that these chars are read out and
-	 * the RX interrupts works as expected.
-	 */
-	rx_fifo_to_buf(dev);
-
-	return plat->rd_ptr != plat->wr_ptr ? 1 : 0;
-}
-
-static int rx_get(struct udevice *dev)
-{
-	struct ns16550_platdata *plat = dev->platdata;
-	char val;
-
-	val = plat->buf[plat->rd_ptr++];
-	plat->rd_ptr %= BUF_COUNT;
-
-	return val;
-}
-
-void ns16550_handle_irq(void *data)
-{
-	struct udevice *dev = (struct udevice *)data;
-	struct NS16550 *const com_port = dev_get_priv(dev);
-
-	/* Check if interrupt is pending */
-	if (serial_in(&com_port->iir) & UART_IIR_NO_INT)
-		return;
-
-	/* Flush all available characters from the RX FIFO into the RX buffer */
-	rx_fifo_to_buf(dev);
-}
-
-#else /* CONFIG_SERIAL_IRQ_BUFFER */
-
-static int rx_pending(struct udevice *dev)
-{
-	struct NS16550 *const com_port = dev_get_priv(dev);
-
-	return serial_in(&com_port->lsr) & UART_LSR_DR ? 1 : 0;
-}
-
-static int rx_get(struct udevice *dev)
-{
-	struct NS16550 *const com_port = dev_get_priv(dev);
-
-	return serial_in(&com_port->rbr);
-}
-
-#endif /* CONFIG_SERIAL_IRQ_BUFFER */
-
 static int ns16550_serial_putc(struct udevice *dev, const char ch)
 {
 	struct NS16550 *const com_port = dev_get_priv(dev);
@@ -413,17 +339,19 @@ static int ns16550_serial_pending(struct udevice *dev, bool input)
 	struct NS16550 *const com_port = dev_get_priv(dev);
 
 	if (input)
-		return rx_pending(dev);
+		return serial_in(&com_port->lsr) & UART_LSR_DR ? 1 : 0;
 	else
 		return serial_in(&com_port->lsr) & UART_LSR_THRE ? 0 : 1;
 }
 
 static int ns16550_serial_getc(struct udevice *dev)
 {
-	if (!ns16550_serial_pending(dev, true))
+	struct NS16550 *const com_port = dev_get_priv(dev);
+
+	if (!(serial_in(&com_port->lsr) & UART_LSR_DR))
 		return -EAGAIN;
 
-	return rx_get(dev);
+	return serial_in(&com_port->rbr);
 }
 
 static int ns16550_serial_setbrg(struct udevice *dev, int baudrate)
@@ -446,40 +374,9 @@ int ns16550_serial_probe(struct udevice *dev)
 	com_port->plat = dev_get_platdata(dev);
 	NS16550_init(com_port, -1);
 
-#if CONFIG_IS_ENABLED(SERIAL_IRQ_BUFFER)
-	if (gd->flags & GD_FLG_RELOC) {
-		struct ns16550_platdata *plat = dev->platdata;
-
-		/* Allocate the RX buffer */
-		plat->buf = malloc(BUF_COUNT);
-
-		/* Install the interrupt handler */
-		irq_install_handler(plat->irq, ns16550_handle_irq, dev);
-
-		/* Enable RX interrupts */
-		serial_out(UART_IER_RDI, &com_port->ier);
-	}
-#endif
-
 	return 0;
 }
 
-#if CONFIG_IS_ENABLED(SERIAL_PRESENT) && \
-	(!defined(CONFIG_TPL_BUILD) || defined(CONFIG_TPL_DM_SERIAL))
-static int ns16550_serial_remove(struct udevice *dev)
-{
-#if CONFIG_IS_ENABLED(SERIAL_IRQ_BUFFER)
-	if (gd->flags & GD_FLG_RELOC) {
-		struct ns16550_platdata *plat = dev->platdata;
-
-		irq_free_handler(plat->irq);
-	}
-#endif
-
-	return 0;
-}
-#endif
-
 #if CONFIG_IS_ENABLED(OF_CONTROL)
 enum {
 	PORT_NS16550 = 0,
@@ -561,15 +458,6 @@ int ns16550_serial_ofdata_to_platdata(struct udevice *dev)
 	if (port_type == PORT_JZ4780)
 		plat->fcr |= UART_FCR_UME;
 
-#if CONFIG_IS_ENABLED(SERIAL_IRQ_BUFFER)
-	plat->irq = fdtdec_get_int(gd->fdt_blob, dev_of_offset(dev),
-				   "interrupts", 0);
-	if (!plat->irq) {
-		debug("ns16550 interrupt not provided\n");
-		return -EINVAL;
-	}
-#endif
-
 	return 0;
 }
 #endif
@@ -617,7 +505,6 @@ U_BOOT_DRIVER(ns16550_serial) = {
 #endif
 	.priv_auto_alloc_size = sizeof(struct NS16550),
 	.probe = ns16550_serial_probe,
-	.remove = ns16550_serial_remove,
 	.ops	= &ns16550_serial_ops,
 	.flags	= DM_FLAG_PRE_RELOC,
 };

include/ns16550.h

@@ -51,10 +51,6 @@
  * @base:		Base register address
  * @reg_shift:		Shift size of registers (0=byte, 1=16bit, 2=32bit...)
  * @clock:		UART base clock speed in Hz
- *
- * @buf:		Pointer to the RX interrupt buffer
- * @rd_ptr:		Read pointer in the RX interrupt buffer
- * @wr_ptr:		Write pointer in the RX interrupt buffer
  */
 struct ns16550_platdata {
 	unsigned long base;
@@ -62,12 +58,6 @@ struct ns16550_platdata {
 	int clock;
 	int reg_offset;
 	u32 fcr;
-
-	int irq;
-
-	char *buf;
-	int rd_ptr;
-	int wr_ptr;
 };
 
 struct udevice;