[PATCH v4 0/4] ACPI: parse the SPCR table

From: Aleksey Makarov
Date: Mon Feb 29 2016 - 07:03:38 EST

'ARM Server Base Boot Requirements' [1] mentions SPCR (Serial Port
Console Redirection Table) [2] as a mandatory ACPI table that
specifies the configuration of serial console.

Introduce a new function acpi_console_check(). At the uart port
registration, this function checks if the ACPI SPCR table specifies
its argument of type struct uart_port to be a console
and if so calls add_preferred_console().

Use SPCR to tell if SBSA serial driver should use 32-bit access to registers.

Based on the work by Leif Lindholm [3]

Should be applied to next-20160229.

Tested on QEMU. SPCR support is included in QEMU's ARM mach-virt
since 2.4 release.

- drop patch "ACPI: change __init to __ref for early_acpi_os_unmap_memory()"
ACPI developers work on a new API and asked not to do that.
Instead, use acpi_get_table_with_size()/early_acpi_os_unmap_memory() once
and cache the result. (Lv Zheng)
- fix some style issues (Yury Norov)


Greg Kroah-Hartman did not like v2 so I have rewritten this patchset:

- drop acpi_match() member of struct console
- drop implementations of this member for pl011 and 8250
- drop the patch that renames some vars in printk.c as it is not needed anymore
- drop patch that introduces system wide acpi_table_parse2().
Instead introduce a custom acpi_table_parse_spcr() in spcr.c

Instead of introducing a new match_acpi() member of struct console,
this patchset introduces a new function acpi_console_check().
This function is called when a new uart is registered at serial_core.c
the same way OF code checks for console. If the registered uart is the
console specified by SPCR table, this function calls add_preferred_console()

The restrictions of this approach are:

- only serial consoles can be set up
- only consoles specified by the memory/io address can be set up
(SPCR can specify devices by PCI id/PCI address)

- don't use SPCR if user specified console in command line
- fix initialization order of newcon->index = 0
- rename some variables at printk.c (Joe Perches, Peter Hurley)
- enable ACPI_SPCR_TABLE in a separate patch (Andy Shevchenko)
- remove the retry loop for console registering (Peter Hurley).
Instead, obtain SPCR with acpi_get_table(). That works after
call to acpi_early_init() i. e. in any *_initcall()
- describe design decision behind introducing acpi_match() (Peter Hurley)
- fix compilation for x86 + ACPI (Graeme Gregory)
- introduce DBG2 constants in a separate patch (Andy Shevchenko)
- fix a typo in DBG2 constants (Andy Shevchenko)
- add ACPI_DBG2_ARM_SBSA_32BIT constant (Christopher Covington)
- add support for ACPI_DBG2_ARM_SBSA_* consoles (Christopher Covington)
- add documentation for functions
- add a patch that uses SPCR to find if SBSA serial driver should use 32-bit
accessor functions (Christopher Covington)
- change __init to __ref for early_acpi_os_unmap_memory() in a separate patch
- introduce acpi_table_parse2() in a separate patch
- fix fetching the SPCR table early (Mark Salter)
- add a patch from Mark Salter that introduces support for matching 8250-based


[1] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.den0044a/index.html
[2] https://msdn.microsoft.com/en-us/library/windows/hardware/dn639132(v=vs.85).aspx
[3] https://lkml.kernel.org/g/1441716217-23786-1-git-send-email-leif.lindholm@xxxxxxxxxx

Aleksey Makarov (4):
ACPI: parse SPCR and enable matching console
ACPI: add definitions of DBG2 subtypes
serial: pl011: use ACPI SPCR to setup 32-bit access

arch/arm64/Kconfig | 1 +
drivers/acpi/Kconfig | 3 +
drivers/acpi/Makefile | 1 +
drivers/acpi/spcr.c | 138 +++++++++++++++++++++++++++++++++++++++
drivers/tty/serial/amba-pl011.c | 2 +
drivers/tty/serial/serial_core.c | 14 +++-
include/acpi/actbl2.h | 5 ++
include/linux/acpi.h | 15 +++++
8 files changed, 177 insertions(+), 2 deletions(-)
create mode 100644 drivers/acpi/spcr.c