linux-kernel - Re: [PATCH v4 0/4] ACPI: parse the SPCR table

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Message-ID: <56D5B5CB.7010702@hurleysoftware.com>
Date:	Tue, 1 Mar 2016 07:31:23 -0800
From:	Peter Hurley <peter@...leysoftware.com>
To:	Aleksey Makarov <aleksey.makarov@...aro.org>,
	linux-acpi@...r.kernel.org
Cc:	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Russell King <linux@....linux.org.uk>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J . Wysocki" <rjw@...ysocki.net>,
	Leif Lindholm <leif.lindholm@...aro.org>,
	Graeme Gregory <graeme.gregory@...aro.org>,
	Al Stone <ahs3@...hat.com>,
	Christopher Covington <cov@...eaurora.org>,
	Yury Norov <ynorov@...iumnetworks.com>,
	"Zheng, Lv" <lv.zheng@...el.com>
Subject: Re: [PATCH v4 0/4] ACPI: parse the SPCR table

On 02/29/2016 04:02 AM, Aleksey Makarov wrote:
> '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().

How will a user enable an earlycon on the same console as the SPCR
console if there is no DBG2 table?


> 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.
> 
> v4:
> - 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)
> 
> v3:
> https://lkml.kernel.org/g/1455559532-8305-1-git-send-email-aleksey.makarov@linaro.org
> 
> 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)
> 
> v2:
> https://lkml.kernel.org/g/1455299022-11641-1-git-send-email-aleksey.makarov@linaro.org
> - 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
>   consoles
> 
> v1:
> https://lkml.kernel.org/g/1453722324-22407-1-git-send-email-aleksey.makarov@linaro.org
> 
> [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@linaro.org
> 
> Aleksey Makarov (4):
>   ACPI: parse SPCR and enable matching console
>   ACPI: enable ACPI_SPCR_TABLE on ARM64
>   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
>