Re: [Qemu-devel] [PATCH v5 0/5] add ACPI node for fw_cfg on pc and arm

[Laszlo Ersek <lersek@redhat.com>]

On 11/23/15 20:31, Gabriel L. Somlo wrote:
> Couple of items:
> 
> 1. Ping ? :)
> 
> 2. Thank you markmb for your R-b !
> 
> 3. If anyone's had a chance to look over the corresponding guest-side
>    kernel sysfs driver which utilizes this, you will have noticed I'm
>    automatically initializing the driver based on DeviceTree or ACPI
>    on ARM and x86, and that there's also the option of passing in
>    command line parameters for the other architectures on which fw_cfg
>    is available (sun4* and ppc/mac).
> 
>    The issue I'm wondering about is that, while architectures where
>    fw_cfg registers show up as IO ports (x86 and sun4u) have the same
>    register_offset:size values (0:2 for control, 1:1 for data), MMIO
>    on everything *other* than ARM is different:
> 
> 	- ARM has 8:2 for control, and 0:8 for data
> 
> 	- sun4m and ppc/mac both have 0:2 for control, and 2:1 for data
> 
>    Right now, neither DeviceTree nor ACPI specify register offsets
>    within the MMIO or PortIO area they associate with fw_cfg:
> 
>   	- ACPI has (in _CRS) either:
> 
>             IO (Decode16,
>                 0x0510,             // Range Minimum
>                 0x0510,             // Range Maximum
>                 0x01,               // Alignment
>                 0x02,               // Length
>                 )
> 
> 	  or:
> 
>             Memory32Fixed (ReadWrite,
>                            0x09020000,  // Address Base
>                            0x0000000a,  // Address Length
>                           )
> 
> 	- DT does something along this lines:
> 
> 	    {
> 	            #size-cells = <0x2>;
> 	            #address-cells = <0x2>;
> 
> 	            fw-cfg@9020000 {
> 	                    compatible = "qemu,fw-cfg-mmio";
> 	                    reg = <0x0 0x9020000 0x0 0xa>;
> 	            };
> 	    };
> 
>   So in the guest-side kernel sysfs driver initialization routine,
>   I need to assume x86 (and, respectively, ARM) register offset:size
>   values unless explicitly provided on the command line.
> 
>   Are we likely to EVER try to supply defaults via DT (or ACPI) for
>   any other architectures besides ARM and x86 ? If so, is there a way
>   to additionally provide offsets (and sizes), besides just the
>   overall range ?

I guess this is where the bindings docs would provide the specification...

Laszlo

> 
>   If we are NOT planning to ever do DT or ACPI outside x86 and ARM,
>   then nevermind I said anything :)
> 
> Thanks much,
> --Gabriel 
> 
> On Fri, Nov 13, 2015 at 09:57:13PM -0500, Gabriel L. Somlo wrote:
>> New since v4:
>>
>> 	- rebased on top of Marc's DMA series
>> 	- drop machine compat dependency for insertion into x86/ssdt
>> 	  (patch 3/5), following agreement between Igor and Eduardo
>> 	- [mm]io register range now covers DMA register as well, if
>> 	  available.
>> 	- s/bios/firmware in doc file updates
>>
>> Thanks,
>>   --Gabriel
>>
>>> New since v3:
>>>
>>> 	- rebased to work on top of 87e896ab (introducing pc-*-25 classes),
>>> 	  inserting fw_cfg acpi node only for machines >= 2.5.
>>>
>>> 	- reintroduce _STA with value 0x0B (bit 2 for u/i visibility turned
>>> 	  off to avoid Windows complaining -- thanks Igor for catching that!)
>>>
>>> If there's any other feedback besides questions regarding the
>>> appropriateness of "QEMU0002" as the value of _HID, please don't hesitate!
>>>
>>>> New since v2:
>>>>
>>>> 	- pc/i386 node in ssdt only on machine types *newer* than 2.4
>>>> 	  (as suggested by Eduardo)
>>>>
>>>> I appreciate any further comments and reviews. Hopefully we can make
>>>> this palatable for upstream, modulo the lingering concerns about whether
>>>> "QEMU0002" is ok to use as the value of _HID, which I'll hopefully get
>>>> sorted out with the kernel crew...
>>>>
>>>>> New since v1:
>>>>>
>>>>> 	- expose control register size (suggested by Marc Marí)
>>>>>
>>>>> 	- leaving out _UID and _STA fields (thanks Shannon & Igor)
>>>>>
>>>>> 	- using "QEMU0002" as the value of _HID (thanks Michael)
>>>>>
>>>>> 	- added documentation blurb to docs/specs/fw_cfg.txt
>>>>> 	  (mainly to record usage of the "QEMU0002" string with fw_cfg).
>>>>>
>>>>>> This series adds a fw_cfg device node to the SSDT (on pc), or to the
>>>>>> DSDT (on arm).
>>>>>>
>>>>>> 	- Patch 1/3 moves (and renames) the BIOS_CFG_IOPORT (0x510)
>>>>>> 	  define from pc.c to pc.h, so that it could be used from
>>>>>> 	  acpi-build.c in patch 2/3.
>>>>>>
>>>>>> 	- Patch 2/3 adds a fw_cfg node to the pc SSDT.
>>>>>>
>>>>>> 	- Patch 3/3 adds a fw_cfg node to the arm DSDT.
>>>>>>
>>>>>> I made up some names - "FWCF" for the node name, and "FWCF0001"
>>>>>> for _HID; no idea whether that's appropriate, or how else I should
>>>>>> figure out what to use instead...
>>>>>>
>>>>>> Also, using scope "\\_SB", based on where fw_cfg shows up in the
>>>>>> output of "info qtree". Again, if that's wrong, please point me in
>>>>>> the right direction.
>>>>>>
>>>>>> Re. 3/3 (also mentioned after the commit blurb in the patch itself),
>>>>>> I noticed none of the other DSDT entries contain a _STA field, wondering
>>>>>> why it would (not) make sense to include that, same as on the PC.
>> Gabriel L. Somlo (5):
>>   fw_cfg: expose control register size in fw_cfg.h
>>   pc: fw_cfg: move ioport base constant to pc.h
>>   acpi: pc: add fw_cfg device node to ssdt
>>   acpi: arm: add fw_cfg device node to dsdt
>>   fw_cfg: document ACPI device node information
>>
>>  docs/specs/fw_cfg.txt     |  9 +++++++++
>>  hw/arm/virt-acpi-build.c  | 15 +++++++++++++++
>>  hw/i386/acpi-build.c      | 29 +++++++++++++++++++++++++++++
>>  hw/i386/pc.c              |  5 ++---
>>  hw/nvram/fw_cfg.c         |  4 +++-
>>  include/hw/i386/pc.h      |  2 ++
>>  include/hw/nvram/fw_cfg.h |  3 +++
>>  7 files changed, 63 insertions(+), 4 deletions(-)
>>
>> -- 
>> 2.4.3
>>