Re: [PATCH V8 5/6] ACPI: Support the probing on the devices which apply indirect-IO

zhichang.yuan
2017-04-21T02:23:08Z

Hi, Dann,

On 04/21/2017 04:57 AM, dann frazier wrote:
> On Thu, Mar 30, 2017 at 9:26 AM, zhichang.yuan
> <yuanzhichang@hisilicon.com> wrote:
>> On some platforms(such as Hip06/Hip07), the legacy ISA/LPC devices access I/O
>> with some special host-local I/O ports known on x86. To access the I/O
>> peripherals, an indirect-IO mechanism is introduced to mapped the host-local
>> I/O to system logical/fake PIO similar the PCI MMIO on architectures where no
>> separate I/O space exists. Just as PCI MMIO, the host I/O range should be
>> registered before probing the downstream devices and set up the I/O mapping.
>> But current ACPI bus probing doesn't support these indirect-IO hosts/devices.
>>
>> This patch introdueces a new ACPI handler for this device category. Through the
>> handler attach callback, the indirect-IO hosts I/O registration is done and
>> all peripherals' I/O resources are translated into logic/fake PIO before
>> starting the enumeration.
>>
>> Signed-off-by: zhichang.yuan <yuanzhichang@hisilicon.com>
>> Signed-off-by: Gabriele Paoloni <gabriele.paoloni@huawei.com>
>> ---
>> drivers/acpi/Makefile | 1 +
>> drivers/acpi/acpi_indirectio.c | 344 +++++++++++++++++++++++++++++++++++++++++
>> drivers/acpi/internal.h | 5 +
>> drivers/acpi/scan.c | 1 +
>> 4 files changed, 351 insertions(+)
>> create mode 100644 drivers/acpi/acpi_indirectio.c
>>
>> diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
>> index a391bbc..10e5f2b 100644
>> --- a/drivers/acpi/Makefile
>> +++ b/drivers/acpi/Makefile
>> @@ -57,6 +57,7 @@ acpi-$(CONFIG_ACPI_PROCFS_POWER) += cm_sbs.o
>> acpi-y += acpi_lpat.o
>> acpi-$(CONFIG_ACPI_GENERIC_GSI) += irq.o
>> acpi-$(CONFIG_ACPI_WATCHDOG) += acpi_watchdog.o
>> +acpi-$(CONFIG_INDIRECT_PIO) += acpi_indirectio.o
>>
>> # These are (potentially) separate modules
>>
>> diff --git a/drivers/acpi/acpi_indirectio.c b/drivers/acpi/acpi_indirectio.c
>> new file mode 100644
>> index 0000000..c8c80b5
>> --- /dev/null
>> +++ b/drivers/acpi/acpi_indirectio.c
>> @@ -0,0 +1,344 @@

[snip]

>> +acpi_build_logiciores_template(struct acpi_device *adev,
>> + struct acpi_buffer *buffer)
>> +{
>> + acpi_handle handle = adev->handle;
>> + struct acpi_resource *resource;
>> + acpi_status status;
>> + int res_cnt = 0;
>> +
>> + status = acpi_walk_resources(handle, METHOD_NAME__CRS,
>> + acpi_count_logiciores, &res_cnt);
>> + if (ACPI_FAILURE(status) || !res_cnt) {
>> + dev_err(&adev->dev, "can't evaluate _CRS: %d\n", status);
>> + return -EINVAL;
>> + }
>> +
>> + buffer->length = sizeof(struct acpi_resource) * (res_cnt + 1) + 1;
>> + buffer->pointer = kzalloc(buffer->length - 1, GFP_KERNEL);
>
> (Seth Forshee noticed this issue, just passing it on)
>
> Should this just allocate the full buffer->length? That would keep the
> length attribute accurate (possibly avoiding an off-by-1 error later).
> It's not clear what the trailing byte is needed for, but other drivers
> allocate it as well (drivers/acpi/pci_link.c and
> drivers/platform/x86/sony-laptop.c).

Thanks for your suggestion!

I also curious why this one appended byte is needed as it seems the later
acpi_set_current_resources() doesn't use this byte.
And I tested without setting the buffer->length as the length of resource list
directly, it seems ok.

But anyway, it looks more reasonable to allocate the memory with the
buffer->length rather than buffer->length - 1;

I was made the V9 patch-set, and I can add your suggestion there. But I also
awaiting for ARM64 ACPI maintainer's comment about this patch before really
sending V9. I wonder whether there is better way to make our indirect-IO devices
can be assigned the logic PIO before the enumeration...

Lorenzo, Hanjun, what do you think about this patch?

Thanks,
Zhichang

>
> -dann
>