Re: [PATCH v7 0/5] ACPI: parse the SPCR table

From: Peter Hurley
Date: Wed Apr 06 2016 - 12:27:40 EST

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On 04/06/2016 07:18 AM, Mark Salter wrote:
> On Wed, 2016-04-06 at 11:52 +0100, Graeme Gregory wrote:
>> On Wed, Apr 06, 2016 at 01:24:12PM +0300, Aleksey Makarov wrote:
>>>
>>>
>>>
>>> On 04/05/2016 07:27 PM, Mark Salter wrote:
>>>>
>>>> Could you CC me on future postings of this series, please?
>>>>
>>>> So v3 fixed a problem where platforms using 8250 didn't work.
>>>> Then in v5, that fix was lost so 8250 no longer works.
>>> That fix was dropped because now this is implemented differently.
>>> Now the code uses the existing match() member of struct console.
>>> It has already been implemented for 8250.
>>> Probably SPCR table specifies incorrect data.
>>> It was reported that D02 board has similar issue.
>>>
>> The D02 issue referred to is the 8250 implementation they used has 32bit
>> only MMIO access which there is no manner to represent in SPCR. It also
>> doesn't use the "standard" 16550 clock rate so supplying a baud rate
>> makes it change to a random baud rate.
>
> So, the problem with Mustang and m400 was the mmio vs mmio32.

Bummer. Maybe that firmware can use a different DBG2 port designation to
indicate it's a DesignWare 8250 (or generically 32-bit mmio).

> Right now,
> the kernel only supports mmio32 in the 8250_dw.c driver when probed with
> ACPI.

While that's true specifically for DesignWare 8250 + ACPI, that's not
true for _all_ 8250 + ACPI.

> Other x86 machines just use legacy 8250 ports which don't need
> entries in the DSDT and use legacy io.

I find that statement hard to believe. I know for a fact ia64 servers didn't,
so the assertion that SPCR + 16550 + MMIO automatically means 32-bit data width
seems unlikely.

In fact, I suspect the opposite is true; that before these arm64 designs,
SPCR + 16550 + MMIO automatically meant 8-bit data width, which is why it's
unspecified in the SPCR table.

Regards,
Peter Hurley

> The 8250_dw driver does support
> non-standard clocks specified in the DSDT. That works fine for Mustang
> and m400.
>
> So with this quick hack, v7 is working with Mustang/m400:
>
> diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c
> index 68ffc33..dade9de 100644
> --- a/drivers/acpi/spcr.c
> +++ b/drivers/acpi/spcr.c
> @@ -37,6 +37,7 @@ int __init parse_spcr(bool earlycon)
> acpi_status status;
> char *uart;
> char *iotype;
> + int mmio;
> int baud_rate;
> int err;
>
> @@ -56,8 +57,8 @@ int __init parse_spcr(bool earlycon)
> goto done;
> }
>
> - iotype = table->serial_port.space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY ?
> - "mmio" : "io";
> + mmio = table->serial_port.space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY;
> + iotype = mmio ? "mmio" : "io";
>
> switch (table->interface_type) {
> case ACPI_DBG2_ARM_SBSA_32BIT:
> @@ -71,6 +72,8 @@ int __init parse_spcr(bool earlycon)
> case ACPI_DBG2_16550_COMPATIBLE:
> case ACPI_DBG2_16550_SUBSET:
> uart = "uart";
> + if (mmio)
> + iotype = "mmio32";
> break;
> default:
> err = -ENOENT;
>
>>
>> We may need two 8250 subset entries, one just means no clock given, and
>> one no clock given + mmio32 only.
>>
>> Graeme
>>
>>
>>>
>>> Thank you
>>> Aleksey Makarov
>>>
>>>>
>>>>
>>>> --Mark
>>>>
>>>>
>>>> On Thu, 2016-03-31 at 16:40 +0300, 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.
>>>>>
>>>>> Move "earlycon" early_param handling to earlycon.c to parse this option once
>>>>>
>>>>> *** PATCH "ACPICA: Headers: Add new constants for the DBG2 ACPI table"
>>>>> *** IS JUST TO ENABLE BUILDING THE PATCHSET ON linux-next
>>>>>
>>>>> Patch "ACPICA: Headers: Add new constants for the DBG2 ACPI table" is required
>>>>> for the next patch. It is taken from ACPICA series [3], but it has not appeared
>>>>> in linux-next yet.
>>>>>
>>>>> Parse SPCR table, setup earlycon and add register specified console.
>>>>>
>>>>> Enable parsing this table on ARM64. Earlycon should be set up
>>>>> as early as possible. ACPI boot tables are mapped in
>>>>> arch/arm64/kernel/acpi.c:acpi_boot_table_init() called from setup_arch()
>>>>> and that's where we parse spcr. So it has to be opted-in per-arch.
>>>>>
>>>>> Implement console_match() for pl011.
>>>>>
>>>>> Based on the work by Leif Lindholm [4]
>>>>> Thanks to Peter Hurley for explaining how this should work.
>>>>>
>>>>> Should be applied to next-20160331.
>>>>>
>>>>> Tested on QEMU. SPCR support is included in QEMU's ARM mach-virt
>>>>> since 2.4 release.
>>>>>
>>>>> v7:
>>>>> - add Acked-by: Rob Herring for "of/serial: move earlycon early_param handling
>>>>> to serial"
>>>>> - call DT earlycon initialization from the arch ACPI code, not from parse_spcr()
>>>>> (Rafael J. Wysocki)
>>>>> - fix a few minor issues (Rafael J. Wysocki)
>>>>>
>>>>> v6:
>>>>> https://lkml.kernel.org/g/1458823925-19560-1-git-send-email-aleksey.makarov@xxxxxxxxxx
>>>>> - add documentation for parse_spcr() functioin (Yury Norov)
>>>>> - don't initialize err variable (Yury Norov)
>>>>> - add __initdata for the earlycon_init_is_deferred flag variable
>>>>> - rename the function exported in "of/serial: move earlycon early_param handling
>>>>> to serial" to avoid clash with the function from arch/microblaze/kernel/prom.c
>>>>> - defer initialization of DT earlycon until DT/ACPI decision is made
>>>>> (Rob Herring, Peter Hurley)
>>>>> - use snprintf instead of sprintf (Andy Shevchenko)
>>>>> - drop patch that adds EARLYCON_DECLARE for pl011 as EARLYCON_DECLARE is
>>>>> equivalent to OF_EARLYCON_DECLARE for 4.6+ (Peter Hurley). This means that
>>>>> SPCR earlycon will not work on the kernels before 4.6
>>>>>
>>>>> v5:
>>>>> https://lkml.kernel.org/g/1458643595-14719-1-git-send-email-aleksey.makarov@xxxxxxxxxx
>>>>> - drop patch "serial: pl011: use ACPI SPCR to setup 32-bit access" because
>>>>> it is ugly. Also because Christopher Covington came with a better solution [5]
>>>>> - remove error message when the table is not provided by ACPI (Andy Shevchenko)
>>>>> - rewrite spcr.c following the suggestions by Peter Hurley
>>>>> - add console_match() for pl011 in a separate patch
>>>>> - add EARLYCON_DECLARE for pl011 in a separate patch
>>>>> - add patch "of/serial: move earlycon early_param handling to serial" from
>>>>> the GDB2 series
>>>>>
>>>>> v4:
>>>>> https://lkml.kernel.org/g/1456747355-15692-1-git-send-email-aleksey.makarov@xxxxxxxxxx
>>>>> - 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@xxxxxxxxxx
>>>>>
>>>>> 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@xxxxxxxxxx
>>>>> - 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@xxxxxxxxxx
>>>>>
>>>>> [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/cover.1458714002.git.lv.zheng@xxxxxxxxx
>>>>> [4] https://lkml.kernel.org/g/1441716217-23786-1-git-send-email-leif.lindholm@xxxxxxxxxx
>>>>> [5] https://lkml.kernel.org/g/1457415800-8799-1-git-send-email-cov@xxxxxxxxxxxxxx
>>>>>
>>>>> Aleksey Makarov (4):
>>>>> ACPICA: Headers: Add new constants for the DBG2 ACPI table
>>>>> ACPI: parse SPCR and enable matching console
>>>>> ARM64: ACPI: enable ACPI_SPCR_TABLE
>>>>> serial: pl011: add console matching function
>>>>>
>>>>> Leif Lindholm (1):
>>>>> of/serial: move earlycon early_param handling to serial
>>>>>
>>>>> arch/arm64/Kconfig | 1 +
>>>>> arch/arm64/kernel/acpi.c | 11 +++-
>>>>> drivers/acpi/Kconfig | 3 ++
>>>>> drivers/acpi/Makefile | 1 +
>>>>> drivers/acpi/spcr.c | 111 ++++++++++++++++++++++++++++++++++++++++
>>>>> drivers/of/fdt.c | 11 +---
>>>>> drivers/tty/serial/amba-pl011.c | 56 ++++++++++++++++++++
>>>>> drivers/tty/serial/earlycon.c | 19 ++++++-
>>>>> include/acpi/actbl2.h | 7 ++-
>>>>> include/linux/acpi.h | 6 +++
>>>>> include/linux/of_fdt.h | 2 +
>>>>> include/linux/serial_core.h | 6 +++
>>>>> 12 files changed, 220 insertions(+), 14 deletions(-)
>>>>> create mode 100644 drivers/acpi/spcr.c
>>>>>
>>> _______________________________________________
>>> linux-arm-kernel mailing list
>>> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
>>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>

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In reply to: Mark Salter: "Re: [PATCH v7 0/5] ACPI: parse the SPCR table"
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