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Date: Thu, 23 Jul 2015 15:21:27 -0700
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Bin Gao <bin.gao@...ux.intel.com>
Cc: One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
Peter Hurley <peter@...leysoftware.com>,
Jiri Slaby <jslaby@...e.cz>, Paul Bolle <pebolle@...cali.nl>,
linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 1/2] serial_core: add pci uart early console support
On Mon, Jun 08, 2015 at 11:17:11AM -0700, Bin Gao wrote:
> 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@...el.com>
> ---
> Changes in v6: None
> Changes in v5:
> - updated Documentation/kernel-parameters.txt.
> - moved earlyprintk= to patch 2/2 (requires x86 people's review).
> - rolled back to simple_strto* APIs.
> - seperate pci/pci32 format description.
> - minor error and debug message changes.
> - if/else statements in uart_parse_earlycon() were refactored to avoid
> logic steering locals.
> Changes in v4:
> - moved PCI_EARLY definition from arch/x86/Kconfig to drivers/pci/Kconfig
> - made earlycon= for all archs but earlyprintk= only for x86 by changing
> "#ifdef #else #endif" to "#if #endif".
> Changes in v3:
> - introduced CONFIG_EARLY_PCI to protect pci codes in serial_core.c.
> - added earlyprintk= as alia to earlycon= to keep x86 compatibility.
> changes in v2:
> - added the second patch (2/2) to remove existed pci early console support
> from arch/x86/kernel/early_printk.c.
> Documentation/kernel-parameters.txt | 15 +++++
> arch/x86/Kconfig | 1 +
> drivers/pci/Kconfig | 11 ++++
> drivers/tty/serial/serial_core.c | 106 +++++++++++++++++++++++++++++++++++-
> 4 files changed, 132 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> index 61ab162..598606e 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -969,6 +969,16 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
> same format described for "console=ttyS<n>"; if
> unspecified, the h/w is not initialized.
>
> + uart8250,pci,<bus:dev.func>[,options]
> + uart8250,pci32,<bus:dev.func>[,options]
> + Start an early, polled-mode console on the 8250/16550
> + UART at the specified PCI device (bus:dev.func).
> + The io or memory mmaped register width is either 8-bit
> + (pci) or 32-bit (pci32).
> + 'options' are specified in the same format described
> + for "console=ttyS<n>"; if unspecified, the h/w is not
> + initialized.
> +
> pl011,<addr>
> Start an early, polled-mode console on a pl011 serial
> port at the specified address. The pl011 serial port
> @@ -1009,6 +1019,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
> earlyprintk=serial[,0x...[,baudrate]]
> earlyprintk=ttySn[,baudrate]
> earlyprintk=dbgp[debugController#]
> + earlyprintk=uart8250,pci,<bus:dev.fun>[,options]
> + earlyprintk=uart8250,pci32,<bus:dev.func>[,options]
>
> earlyprintk is useful when the kernel crashes before
> the normal console is initialized. It is not enabled by
> @@ -1037,6 +1049,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
>
> The xen output can only be used by Xen PV guests.
>
> + The uart8250,pci and uart8250,pci32 output share the
> + same definition that is in earlycon= section.
> +
> edac_report= [HW,EDAC] Control how to report EDAC event
> Format: {"on" | "off" | "force"}
> on: enable EDAC to report H/W event. May be overridden
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 226d569..bdedd61 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -143,6 +143,7 @@ config X86
> select ACPI_LEGACY_TABLES_LOOKUP if ACPI
> select X86_FEATURE_NAMES if PROC_FS
> select SRCU
> + select PCI_EARLY if PCI
>
> config INSTRUCTION_DECODER
> def_bool y
> diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
> index 7a8f1c5..4f0f055 100644
> --- a/drivers/pci/Kconfig
> +++ b/drivers/pci/Kconfig
> @@ -114,4 +114,15 @@ config PCI_LABEL
> def_bool y if (DMI || ACPI)
> select NLS
>
> +config PCI_EARLY
> + bool "Early PCI access"
> + depends on PCI
> + default n
Default is always 'n' so this isn't needed here.
> + 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 should enable this option which is required by
> + arch independent codes, e.g. uart8250 pci early console driver.
> +
> source "drivers/pci/host/Kconfig"
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index 0b7bb12..5b21999 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_PCI_EARLY
> +#include <asm/pci-direct.h>
> +#endif
You shouldn't need an #ifdef here, the .h file should handle it. Why
doesn't pci.h always include this if it is present?
thanks,
greg k-h
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