8250_ce4100.c

 1// SPDX-License-Identifier: GPL-2.0-only
 2/*
 3 * Intel CE4100  platform specific setup code
 4 *
 5 * (C) Copyright 2010 Intel Corporation
 6 */
 7
 8#include <linux/init.h>
 9#include <linux/io.h>
10#include <linux/types.h>
11
12#include <asm/ce4100.h>
13#include <asm/fixmap.h>
14#include <asm/page.h>
15
16#include <linux/serial_reg.h>
17#include <linux/serial_8250.h>
18
19static unsigned int mem_serial_in(struct uart_port *p, int offset)
20{
21	offset = offset << p->regshift;
22	return readl(p->membase + offset);
23}
24
25/*
26 * The UART Tx interrupts are not set under some conditions and therefore serial
27 * transmission hangs. This is a silicon issue and has not been root caused. The
28 * workaround for this silicon issue checks UART_LSR_THRE bit and UART_LSR_TEMT
29 * bit of LSR register in interrupt handler to see whether at least one of these
30 * two bits is set, if so then process the transmit request. If this workaround
31 * is not applied, then the serial transmission may hang. This workaround is for
32 * errata number 9 in Errata - B step.
33*/
34static u32 ce4100_mem_serial_in(struct uart_port *p, unsigned int offset)
35{
36	u32 ret, ier, lsr;
37
38	ret = mem_serial_in(p, offset);
39	if (offset != UART_IIR || !(ret & UART_IIR_NO_INT))
40		return ret;
41
42	/* see if the TX interrupt should have really set */
43	ier = mem_serial_in(p, UART_IER);
44	/* see if the UART's XMIT interrupt is enabled */
45	if (!(ier & UART_IER_THRI))
46		return ret;
47
48	lsr = mem_serial_in(p, UART_LSR);
49	/* now check to see if the UART should be generating an interrupt (but isn't) */
50	if (lsr & (UART_LSR_THRE | UART_LSR_TEMT))
51		ret &= ~UART_IIR_NO_INT;
52
53	return ret;
54}
55
56static void ce4100_mem_serial_out(struct uart_port *p, unsigned int offset, u32 value)
57{
58	offset <<= p->regshift;
59	writel(value, p->membase + offset);
60}
61
62static void ce4100_serial_fixup(int port, struct uart_port *up, u32 *capabilities)
63{
64#ifdef CONFIG_EARLY_PRINTK
65	/*
66	 * Override the legacy port configuration that comes from
67	 * asm/serial.h. Using the ioport driver then switching to the
68	 * PCI memmaped driver hangs the IOAPIC.
69	 */
70	if (up->iotype != UPIO_MEM32) {
71		up->uartclk = 14745600;
72		up->mapbase = 0xdffe0200;
73		set_fixmap_nocache(FIX_EARLYCON_MEM_BASE, up->mapbase & PAGE_MASK);
74		up->membase = (void __iomem *)__fix_to_virt(FIX_EARLYCON_MEM_BASE);
75		up->membase += up->mapbase & ~PAGE_MASK;
76		up->mapbase += port * 0x100;
77		up->membase += port * 0x100;
78		up->iotype = UPIO_MEM32;
79		up->regshift = 2;
80		up->irq = 4;
81	}
82#endif
83	up->iobase = 0;
84	up->serial_in = ce4100_mem_serial_in;
85	up->serial_out = ce4100_mem_serial_out;
86
87	*capabilities |= (1 << 12);
88}
89
90void __init sdv_serial_fixup(void)
91{
92	serial8250_set_isa_configurator(ce4100_serial_fixup);
93}