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 <[email protected]>
---
arch/x86/Kconfig | 11 +++
drivers/tty/serial/earlycon.c | 9 +++
drivers/tty/serial/serial_core.c | 145 ++++++++++++++++++++++++++++++++++++++-
3 files changed, 163 insertions(+), 2 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 226d569..1283220 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2228,6 +2228,8 @@ config PCI
your box. Other bus systems are ISA, EISA, MicroChannel (MCA) or
VESA. If you have PCI, say Y, otherwise N.
+ select HAVE_EARLY_PCI
+
choice
prompt "PCI access mode"
depends on X86_32 && PCI
@@ -2265,6 +2267,15 @@ config PCI_GOANY
endchoice
+config HAVE_EARLY_PCI
+ def_bool y
+ help
+ This option indicates that a group of APIs are available (in
+ asm/pci-direct.h) so the kernel can access pci config registers
+ before the PCI subsystem is initialized. Any arch that supports
+ early pci APIs must enable this option which is required by arch
+ independent codes, e.g. uart8250 pci early console driver.
+
config PCI_BIOS
def_bool y
depends on X86_32 && PCI && (PCI_GOBIOS || PCI_GOANY)
diff --git a/drivers/tty/serial/earlycon.c b/drivers/tty/serial/earlycon.c
index 6dc471e..63ae60e 100644
--- a/drivers/tty/serial/earlycon.c
+++ b/drivers/tty/serial/earlycon.c
@@ -193,6 +193,15 @@ static int __init param_setup_earlycon(char *buf)
}
early_param("earlycon", param_setup_earlycon);
+/* x86 uses "earlyprintk=xxx", so we keep the compatibility here */
+#ifdef CONFIG_X86
+static int __init param_setup_earlycon_x86(char *buf)
+{
+ return param_setup_earlycon(buf);
+}
+early_param("earlyprintk", param_setup_earlycon_x86);
+#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..06218f5 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -34,10 +34,15 @@
#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>
+#ifdef CONFIG_HAVE_EARLY_PCI
+#include <asm/pci-direct.h>
+#endif
+
/*
* This is used to lock changes in serial line configuration.
*/
@@ -1808,6 +1813,110 @@ uart_get_console(struct uart_port *ports, int nr, struct console *co)
return ports + idx;
}
+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;
+}
+
+#ifdef CONFIG_HAVE_EARLY_PCI
+/*
+ * 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;
+
+ if (!early_pci_allowed()) {
+ pr_err("earlycon pci not available(early pci not allowed)\n");
+ return -EINVAL;
+ }
+
+ /* 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;
+}
+
+#else
+static int parse_pci_options(char *options, unsigned long *phys)
+{
+ pr_err("earlycon pci not available(need CONFIG_HAVE_EARLY_PCI)\n");
+ return -EINVAL;
+}
+#endif
+
/**
* uart_parse_earlycon - Parse earlycon options
* @p: ptr to 2nd field (ie., just beyond '<name>,')
@@ -1816,8 +1925,9 @@ 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 +1939,23 @@ 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)
{
+ int pci = 0, ret;
+ unsigned long phys;
+
if (strncmp(p, "mmio,", 5) == 0) {
*iotype = UPIO_MEM;
p += 5;
} else if (strncmp(p, "mmio32,", 7) == 0) {
*iotype = UPIO_MEM32;
p += 7;
+ } 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);
} else if (strncmp(p, "io,", 3) == 0) {
*iotype = UPIO_PORT;
p += 3;
@@ -1844,7 +1965,27 @@ int uart_parse_earlycon(char *p, unsigned char *iotype, unsigned long *addr,
return -EINVAL;
}
- *addr = simple_strtoul(p, NULL, 0);
+ 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
+ *addr = simple_strtoul(p, NULL, 0);
+
p = strchr(p, ',');
if (p)
p++;
--
1.9.1
On Mon, 2015-05-18 at 14:21 -0700, Bin Gao wrote:
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2228,6 +2228,8 @@ config PCI
> your box. Other bus systems are ISA, EISA, MicroChannel (MCA) or
> VESA. If you have PCI, say Y, otherwise N.
>
> + select HAVE_EARLY_PCI
> +
It's legal to have options after the help text of a Kconfig entry. It's
also very uncommon to do that. Please put this select statement before
the line reading "---help---" of the PCI entry.
> +config HAVE_EARLY_PCI
> + def_bool y
You probably want just
bool
here. Because this symbol has no further dependencies, which means
HAVE_EARLY_PCI will now always be set to 'y'. That, in turn, makes the
select you added above pointless.
> + help
> + This option indicates that a group of APIs are available (in
> + asm/pci-direct.h) so the kernel can access pci config registers
> + before the PCI subsystem is initialized. Any arch that supports
Is this expected to be used outside of X86?
> + early pci APIs must enable this option which is required by arch
> + independent codes, e.g. uart8250 pci early console driver.
> +
Thanks,
Paul Bolle
On Tue, May 19, 2015 at 02:01:07PM +0200, Paul Bolle wrote:
> On Mon, 2015-05-18 at 14:21 -0700, Bin Gao wrote:
> > --- a/arch/x86/Kconfig
> > +++ b/arch/x86/Kconfig
> > @@ -2228,6 +2228,8 @@ config PCI
> > your box. Other bus systems are ISA, EISA, MicroChannel (MCA) or
> > VESA. If you have PCI, say Y, otherwise N.
> >
> > + select HAVE_EARLY_PCI
> > +
>
> It's legal to have options after the help text of a Kconfig entry. It's
> also very uncommon to do that. Please put this select statement before
> the line reading "---help---" of the PCI entry.
>
Will fix this in next patch set.
> > +config HAVE_EARLY_PCI
> > + def_bool y
>
> You probably want just
> bool
>
> here. Because this symbol has no further dependencies, which means
> HAVE_EARLY_PCI will now always be set to 'y'. That, in turn, makes the
> select you added above pointless.
>
Yes, you're right. bool is better.
> > + help
> > + This option indicates that a group of APIs are available (in
> > + asm/pci-direct.h) so the kernel can access pci config registers
> > + before the PCI subsystem is initialized. Any arch that supports
>
> Is this expected to be used outside of X86?
Yes, drivers/tty/serial/serial_core.c is going to use it.
On Tue, 2015-05-19 at 10:32 -0700, Bin Gao wrote:
> On Tue, May 19, 2015 at 02:01:07PM +0200, Paul Bolle wrote:
> > Is this expected to be used outside of X86?
> Yes, drivers/tty/serial/serial_core.c is going to use it.
What I should have asked is: do you expect architectures other than X86
to set HAVE_EARLY_PCI? Because then you should put that Kconfig entry in
a file reachable by all architectures. Say, in init/Kconfig or in
drivers/tty/serial/Kconfig.
(You can also have an entry for HAVE_EARLY_PCI for each arch that needs
it, but that would be a bit silly.)
Thanks,
Paul Bolle
On Wed, 2015-05-20 at 10:59 -0700, Bin Gao wrote:
> The HAVE_EARLY_PCI entry should be actually in generic PCI layer,
> i.e. drivers/pci, because it's a PCI feature but only some archs
> (currently only x86) support it.
> Then an arch with this feature could announce it in arch/<arch>/Kconfig by:
> select HAVE_EARLY_PCI if PCI
That makes more sense. So v4 will put HAVE_EARLY_PCI in a Kconfig under
drivers/pci/?
Thanks,
Paul Bolle
On Wed, May 20, 2015 at 11:16:25AM +0200, Paul Bolle wrote:
> What I should have asked is: do you expect architectures other than X86
> to set HAVE_EARLY_PCI? Because then you should put that Kconfig entry in
> a file reachable by all architectures. Say, in init/Kconfig or in
> drivers/tty/serial/Kconfig.
>
> (You can also have an entry for HAVE_EARLY_PCI for each arch that needs
> it, but that would be a bit silly.)
>
The HAVE_EARLY_PCI entry should be actually in generic PCI layer,
i.e. drivers/pci, because it's a PCI feature but only some archs
(currently only x86) support it.
Then an arch with this feature could announce it in arch/<arch>/Kconfig by:
select HAVE_EARLY_PCI if PCI
On Wed, May 20, 2015 at 07:50:12PM +0200, Paul Bolle wrote:
> That makes more sense. So v4 will put HAVE_EARLY_PCI in a Kconfig under
> drivers/pci/?
>
Yes.