serial_core: add pci uart early console support

serial_core: add pci uart early console support

[Bin Gao]

>From 8977941ac3d70425fa7ca5ef3ab6de6c28743f1f Mon Sep 17 00:00:00 2001
From: Bin Gao <bin.gao@intel.com>
Date: Tue, 12 May 2015 16:40:27 -0700
Subject: [PATCH] serial_core: add pci uart early console support

On some Intel Atom SoCs, the legacy IO port UART(0x3F8) is not available.
Instead, a 8250 compatible PCI uart can be used as early console.
This patch adds pci support to the 8250 early console driver uart8250.
For example, to enable pci uart(00:21.3) as early console on these
platforms, append the following line to the kernel command line
(assume baud rate is 115200):
earlycon=uart8250,pci32,0:24.2,115200n8

Signed-off-by: Bin Gao <bin.gao@intel.com>
---
 drivers/tty/serial/serial_core.c | 140 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 138 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 0b7bb12..221143c 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -34,10 +34,16 @@
 #include <linux/serial_core.h>
 #include <linux/delay.h>
 #include <linux/mutex.h>
+#include <linux/pci_regs.h>
 
 #include <asm/irq.h>
 #include <asm/uaccess.h>
 
+/* Only x86 has early pci access APIs */
+#if defined(CONFIG_PCI) && defined(CONFIG_X86)
+#include <asm/pci-direct.h>
+#endif
+
 /*
  * This is used to lock changes in serial line configuration.
  */
@@ -1808,6 +1814,98 @@ uart_get_console(struct uart_port *ports, int nr, struct console *co)
 	return ports + idx;
 }
 
+#if defined(CONFIG_PCI) && defined(CONFIG_X86)
+static int parse_bdf(char *options, char **endp, char delimiter, u8 *val)
+{
+	char str[4]; /* max 3 chars, plus a NULL terminator */
+	char *p = options;
+	int i = 0;
+
+	while (*p) {
+		if (i >= 4)
+			return -EINVAL;
+
+		if (*p == delimiter) {
+			str[i++] = 0;
+			if (endp)
+				*endp = p + 1;
+			return kstrtou8(str, 10, val); /* decimal, no hex */
+		}
+
+		str[i++] = *p++;
+	}
+
+	return -EINVAL;
+}
+
+/*
+ * The whole pci option from the command line is: pci[32],B:D.F[,options]
+ * Examples:
+ *     pci,0:21.3,115200n8
+ *     pci32,0:21.3
+ * Here pci32 means 8250 UART registers are 32-bit width(regshift = 2).
+ * pci means 8250 UART registers are 8-bit width(regshift = 0).
+ * B,D and F are bus, device and function, in decimal(not hex).
+ * The additional options(115200n8) would be parsed by the earlycon framework.
+ *
+ * @options: the pci options
+ * @phys: the pointer to return pci mem or io address
+ * return: <0: error
+ *          0: pci mem
+ *          1: pci io
+ */
+static int parse_pci_options(char *options, unsigned long *phys)
+{
+	u8 bus, dev, func;
+	char *endp;
+	u64 bar0;
+	u16 cmd;
+	int pci_io = 0;
+
+	/* We come here with options=B:D.F[,options] */
+	if (parse_bdf(options, &endp, ':', &bus))
+		goto failed;
+
+	if (parse_bdf(endp, &endp, '.', &dev))
+		goto failed;
+
+	if (parse_bdf(endp, &endp, ',', &func))
+		goto failed;
+
+	/*
+	 * On these platforms class code in pci config is broken,
+	 * so skip checking it.
+	 */
+
+	bar0 = read_pci_config(bus, dev, func, PCI_BASE_ADDRESS_0);
+
+	/* The BAR is IO or Memory? */
+	if ((bar0 & PCI_BASE_ADDRESS_SPACE) == PCI_BASE_ADDRESS_SPACE_IO)
+		pci_io = 1;
+
+	if ((bar0 & PCI_BASE_ADDRESS_MEM_TYPE_MASK) ==
+			PCI_BASE_ADDRESS_MEM_TYPE_64)
+		bar0 |= (u64)read_pci_config(bus, dev, func,
+				PCI_BASE_ADDRESS_0 + 4) << 32;
+
+	*phys = bar0 & (pci_io ? PCI_BASE_ADDRESS_IO_MASK :
+				 PCI_BASE_ADDRESS_MEM_MASK);
+
+	/* Enable address decoding */
+	cmd = read_pci_config_16(bus, dev, func, PCI_COMMAND);
+	write_pci_config_16(bus, dev, func, PCI_COMMAND,
+		cmd | (pci_io ? PCI_COMMAND_IO : PCI_COMMAND_MEMORY));
+
+	pr_info("Use 8250 uart at PCI 0000:%02u:%02u.%01u as early console\n",
+							bus, dev, func);
+	return pci_io;
+
+failed:
+	pr_err("Invalid earlycon pci parameters\n");
+	return -EINVAL;
+}
+#endif
+
 /**
  *	uart_parse_earlycon - Parse earlycon options
  *	@p:	  ptr to 2nd field (ie., just beyond '<name>,')
@@ -1816,8 +1914,9 @@ uart_get_console(struct uart_port *ports, int nr, struct console *co)
  *	@options: ptr for <options> field; NULL if not present (out)
  *
  *	Decodes earlycon kernel command line parameters of the form
- *	   earlycon=<name>,io|mmio|mmio32,<addr>,<options>
+ *	   earlycon=<name>,io|mmio|mmio32|pci|pci32,<addr>,<options>
  *	   console=<name>,io|mmio|mmio32,<addr>,<options>
+ *	For pci/pci32, the <addr> format is B:D.F, e.g. 0:24.2
  *
  *	The optional form
  *	   earlycon=<name>,0x<addr>,<options>
@@ -1829,12 +1928,27 @@ uart_get_console(struct uart_port *ports, int nr, struct console *co)
 int uart_parse_earlycon(char *p, unsigned char *iotype, unsigned long *addr,
 			char **options)
 {
+#if defined(CONFIG_PCI) && defined(CONFIG_X86)
+	int pci = 0, ret;
+	unsigned long phys;
+#endif
+
 	if (strncmp(p, "mmio,", 5) == 0) {
 		*iotype = UPIO_MEM;
 		p += 5;
 	} else if (strncmp(p, "mmio32,", 7) == 0) {
 		*iotype = UPIO_MEM32;
 		p += 7;
+#if defined(CONFIG_PCI) && defined(CONFIG_X86)
+	} else if (strncmp(p, "pci,", 4) == 0) {
+		pci = 1;
+		p += 4;
+		ret = parse_pci_options(p, &phys);
+	} else if (strncmp(p, "pci32,", 6) == 0) {
+		pci = 2;
+		p += 6;
+		ret = parse_pci_options(p, &phys);
+#endif
 	} else if (strncmp(p, "io,", 3) == 0) {
 		*iotype = UPIO_PORT;
 		p += 3;
@@ -1844,7 +1958,29 @@ int uart_parse_earlycon(char *p, unsigned char *iotype, unsigned long *addr,
 		return -EINVAL;
 	}
 
-	*addr = simple_strtoul(p, NULL, 0);
+#if defined(CONFIG_PCI) && defined(CONFIG_X86)
+	if (pci) {
+		if (ret < 0) /* error */
+			return ret;
+
+		/*
+		 * Once PCI mem/io is read from PCI BAR, we can reuse
+		 * mmio/mmio32/io type to minimize code change.
+		 */
+		if (ret > 0) /* PCI io */
+			*iotype = UPIO_PORT;
+		else { /* ret = 0: PCI mem */
+			if (pci == 2)
+				*iotype = UPIO_MEM32;
+			else
+				*iotype = UPIO_MEM;
+		}
+
+		*addr = phys;
+	} else
+#endif
+		*addr = simple_strtoul(p, NULL, 0);
+
 	p = strchr(p, ',');
 	if (p)
 		p++;
-- 
1.9.1

Re: serial_core: add pci uart early console support

[One Thousand Gnomes]

On Wed, 13 May 2015 12:20:16 -0700
Bin Gao <bin.gao@linux.intel.com> wrote:

> >From 8977941ac3d70425fa7ca5ef3ab6de6c28743f1f Mon Sep 17 00:00:00 2001
> From: Bin Gao <bin.gao@intel.com>
> Date: Tue, 12 May 2015 16:40:27 -0700
> Subject: [PATCH] serial_core: add pci uart early console support
> 
> On some Intel Atom SoCs, the legacy IO port UART(0x3F8) is not available.
> Instead, a 8250 compatible PCI uart can be used as early console.
> This patch adds pci support to the 8250 early console driver uart8250.
> For example, to enable pci uart(00:21.3) as early console on these
> platforms, append the following line to the kernel command line
> (assume baud rate is 115200):
> earlycon=uart8250,pci32,0:24.2,115200n8


We've already got support for this

commit ea9e9d8029020d438b0717ffddf65140fda16051


I actually think the fact you've put it into drivers/tty is better as PCI
is generic and PCI serial boot likewise. However it ought to use the same
command line interface (with extensions) to be compatible with the
existing arch/x86 code, and to remove the arch/x86 version if you are
doing so.

Alan

Re: serial_core: add pci uart early console support

[Bin Gao]

> On Wed, May 13, 2015 at 11:08:44PM +0100, One Thousand Gnomes wrote:
> 
> We've already got support for this
> 
> commit ea9e9d8029020d438b0717ffddf65140fda16051
> 
> 
> I actually think the fact you've put it into drivers/tty is better as PCI
> is generic and PCI serial boot likewise. However it ought to use the same
> command line interface (with extensions) to be compatible with the
> existing arch/x86 code, and to remove the arch/x86 version if you are
> doing so.
> 
> Alan

So now I'm sending two patches:
[PATCH 1/2] serial_core: add pci uart early console support
[PATCH 2/2] arch/x86: remove pci uart early console from early_prink.c