serial: 8250: Move CE4100 quirks to a module under 8250 driver

There is inconvenient for maintainers and maintainership to have
some quirks under architectural code. Move it to the specific quirk
file like other 8250-compatible drivers do.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20250627182743.1273326-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 99 insertions, 0 deletions

diff --git a/drivers/tty/serial/8250/8250_ce4100.c b/drivers/tty/serial/8250/8250_ce4100.c
new file mode 100644
index 000000000000..3dd88f372a51
--- /dev/null
+++ b/drivers/tty/serial/8250/8250_ce4100.c
@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Intel CE4100  platform specific setup code
+ *
+ * (C) Copyright 2010 Intel Corporation
+ */
+
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/types.h>
+
+#include <asm/ce4100.h>
+#include <asm/fixmap.h>
+#include <asm/page.h>
+
+#include <linux/serial_reg.h>
+#include <linux/serial_8250.h>
+
+static unsigned int mem_serial_in(struct uart_port *p, int offset)
+{
+	offset = offset << p->regshift;
+	return readl(p->membase + offset);
+}
+
+/*
+ * The UART Tx interrupts are not set under some conditions and therefore serial
+ * transmission hangs. This is a silicon issue and has not been root caused. The
+ * workaround for this silicon issue checks UART_LSR_THRE bit and UART_LSR_TEMT
+ * bit of LSR register in interrupt handler to see whether at least one of these
+ * two bits is set, if so then process the transmit request. If this workaround
+ * is not applied, then the serial transmission may hang. This workaround is for
+ * errata number 9 in Errata - B step.
+*/
+static u32 ce4100_mem_serial_in(struct uart_port *p, unsigned int offset)
+{
+	u32 ret, ier, lsr;
+
+	if (offset != UART_IIR)
+		return mem_serial_in(p, offset);
+
+	offset <<= p->regshift;
+
+	ret = readl(p->membase + offset);
+	if (!(ret & UART_IIR_NO_INT))
+		return ret;
+
+	/* see if the TX interrupt should have really set */
+	ier = mem_serial_in(p, UART_IER);
+	/* see if the UART's XMIT interrupt is enabled */
+	if (!(ier & UART_IER_THRI))
+		return ret;
+
+	lsr = mem_serial_in(p, UART_LSR);
+	/* now check to see if the UART should be generating an interrupt (but isn't) */
+	if (lsr & (UART_LSR_THRE | UART_LSR_TEMT))
+		ret &= ~UART_IIR_NO_INT;
+
+	return ret;
+}
+
+static void ce4100_mem_serial_out(struct uart_port *p, unsigned int offset, u32 value)
+{
+	offset <<= p->regshift;
+	writel(value, p->membase + offset);
+}
+
+static void ce4100_serial_fixup(int port, struct uart_port *up, u32 *capabilities)
+{
+#ifdef CONFIG_EARLY_PRINTK
+	/*
+	 * Override the legacy port configuration that comes from
+	 * asm/serial.h. Using the ioport driver then switching to the
+	 * PCI memmaped driver hangs the IOAPIC.
+	 */
+	if (up->iotype != UPIO_MEM32) {
+		up->uartclk = 14745600;
+		up->mapbase = 0xdffe0200;
+		set_fixmap_nocache(FIX_EARLYCON_MEM_BASE, up->mapbase & PAGE_MASK);
+		up->membase = (void __iomem *)__fix_to_virt(FIX_EARLYCON_MEM_BASE);
+		up->membase += up->mapbase & ~PAGE_MASK;
+		up->mapbase += port * 0x100;
+		up->membase += port * 0x100;
+		up->iotype = UPIO_MEM32;
+		up->regshift = 2;
+		up->irq = 4;
+	}
+#endif
+	up->iobase = 0;
+	up->serial_in = ce4100_mem_serial_in;
+	up->serial_out = ce4100_mem_serial_out;
+
+	*capabilities |= (1 << 12);
+}
+
+void __init sdv_serial_fixup(void)
+{
+	serial8250_set_isa_configurator(ce4100_serial_fixup);
+}
diff --git a/drivers/tty/serial/8250/Makefile b/drivers/tty/serial/8250/Makefile
index b04eeda03b23..e61dc3f4ca50 100644
--- a/drivers/tty/serial/8250/Makefile
+++ b/drivers/tty/serial/8250/Makefile
@@ -24,6 +24,7 @@ obj-$(CONFIG_SERIAL_8250_ASPEED_VUART)	+= 8250_aspeed_vuart.o
 obj-$(CONFIG_SERIAL_8250_BCM2835AUX)	+= 8250_bcm2835aux.o
 obj-$(CONFIG_SERIAL_8250_BCM7271)	+= 8250_bcm7271.o
 obj-$(CONFIG_SERIAL_8250_BOCA)		+= 8250_boca.o
+obj-$(CONFIG_X86_INTEL_CE)		+= 8250_ce4100.o
 obj-$(CONFIG_SERIAL_8250_DFL)		+= 8250_dfl.o
 obj-$(CONFIG_SERIAL_8250_DW)		+= 8250_dw.o
 obj-$(CONFIG_SERIAL_8250_EM)		+= 8250_em.o