[PATCH v2 1/2] serial_core: add pci uart early console support

[PATCH v2 1/2] serial_core: add pci uart early console support

[Bin Gao]

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):
earlyprintk=uart8250,pci32,0:24.2,115200n8

Signed-off-by: Bin Gao <bin.gao@intel.com>
---
 drivers/tty/serial/earlycon.c    |   6 ++
 drivers/tty/serial/serial_core.c | 140 ++++++++++++++++++++++++++++++++++++++-
 2 files changed, 144 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/earlycon.c b/drivers/tty/serial/earlycon.c
index 5fdc9f3..586d84b 100644
--- a/drivers/tty/serial/earlycon.c
+++ b/drivers/tty/serial/earlycon.c
@@ -196,7 +196,13 @@ static int __init param_setup_earlycon(char *buf)
 	}
 	return err;
 }
+
+/* x86 uses "earlyprintk=xxx", so we keep the compatibility here */
+#ifdef CONFIG_X86
+early_param("earlyprintk", param_setup_earlycon);
+#else
 early_param("earlycon", param_setup_earlycon);
+#endif
 
 int __init of_setup_earlycon(unsigned long addr,
 			     int (*setup)(struct earlycon_device *, const char *))
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: [PATCH v2 1/2] serial_core: add pci uart early console support

[One Thousand Gnomes]

> +/* x86 uses "earlyprintk=xxx", so we keep the compatibility here */
> +#ifdef CONFIG_X86
> +early_param("earlyprintk", param_setup_earlycon);
> +#else
>  early_param("earlycon", param_setup_earlycon);
> +#endif

Is there any reason for not just allowing both ? That way you don't need
an ifdef and the same command line (either) works everywhere ?

>  
>  int __init of_setup_earlycon(unsigned long addr,
>  			     int (*setup)(struct earlycon_device *, const char *))
> 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

We should probably make that a define or Kconfig value so that any other
port wanting early PCI console can add the needed direct functions
without the defines here getting longer and longer

It would then be a single

#if defined(CONFIG_EARLY_PCI)

that could be put anywhere


> +static int parse_pci_options(char *options, unsigned long *phys)
> +{
> +	u8 bus, dev, func;

...

> +failed:
> +	pr_err("Invalid earlycon pci parameters\n");
> +	return -EINVAL;
> +}

#else
static int parse_pci_options(char *options, unsigned long *phys)
{
	pr_err("earlycon pci not available\n");
	return -EINVAL;
}
> +#endif
> +


The all the ifdef mess below goes away

Alan