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SubjectRe: [PATCH] ACPI: SPCR: Use access width to determine mmio usage
On Thu, May 4, 2017 at 12:28 PM, Moore, Robert <robert.moore@intel.com> wrote:
> Jon,
>
> You might want to take a look at using the acpi_read and acpi_write ACPICA interfaces that accept a GAS structure and handle the access width (etc.) automatically.
>
> Bob

This function in SPCR is using common code for the early console. So
the acpi_read/write would not be usable in that common code.

Thanks,
Jon

>
>
>> -----Original Message-----
>> From: Jon Mason [mailto:jon.mason@broadcom.com]
>> Sent: Thursday, May 4, 2017 8:06 AM
>> To: Rafael Wysocki <rjw@rjwysocki.net>; Len Brown <lenb@kernel.org>;
>> Moore, Robert <robert.moore@intel.com>; Zheng, Lv <lv.zheng@intel.com>
>> Cc: linux-acpi@vger.kernel.org; linux-kernel@vger.kernel.org;
>> devel@acpica.org; bcm-kernel-feedback-list@broadcom.com
>> Subject: [PATCH] ACPI: SPCR: Use access width to determine mmio usage
>>
>> The current SPCR code does not check the access width of the mmio, and
>> uses a default of 8bit register accesses. This prevents devices that
>> only do 16 or 32bit register accesses from working. By simply checking
>> this field and setting the mmio string appropriately, this issue can be
>> corrected. To prevent any legacy issues, the code will default to 8bit
>> accesses if the value is anything but 16 or 32.
>>
>> Signed-off-by: Jon Mason <jon.mason@broadcom.com>
>> ---
>> drivers/acpi/spcr.c | 18 ++++++++++++++++--
>> include/acpi/acrestyp.h | 7 +++++++
>> 2 files changed, 23 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c index
>> 01c9466..11233f6 100644
>> --- a/drivers/acpi/spcr.c
>> +++ b/drivers/acpi/spcr.c
>> @@ -74,8 +74,22 @@ int __init parse_spcr(bool earlycon)
>> goto done;
>> }
>>
>> - iotype = table->serial_port.space_id ==
>> ACPI_ADR_SPACE_SYSTEM_MEMORY ?
>> - "mmio" : "io";
>> + if (table->serial_port.space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
>> + switch (table->serial_port.access_width) {
>> + default:
>> + pr_err("Unexpected SPCR Access Width. Defaulting to
>> byte size\n");
>> + case ACPI_ACCESS_SIZE_BYTE:
>> + iotype = "mmio";
>> + break;
>> + case ACPI_ACCESS_SIZE_WORD:
>> + iotype = "mmio16";
>> + break;
>> + case ACPI_ACCESS_SIZE_DWORD:
>> + iotype = "mmio32";
>> + break;
>> + }
>> + } else
>> + iotype = "io";
>>
>> switch (table->interface_type) {
>> case ACPI_DBG2_ARM_SBSA_32BIT:
>> diff --git a/include/acpi/acrestyp.h b/include/acpi/acrestyp.h index
>> f0f7403..781cb55 100644
>> --- a/include/acpi/acrestyp.h
>> +++ b/include/acpi/acrestyp.h
>> @@ -372,6 +372,13 @@ struct acpi_resource_generic_register {
>> u64 address;
>> };
>>
>> +/* Generic Address Space Access Sizes */
>> +#define ACPI_ACCESS_SIZE_UNDEFINED 0
>> +#define ACPI_ACCESS_SIZE_BYTE 1
>> +#define ACPI_ACCESS_SIZE_WORD 2
>> +#define ACPI_ACCESS_SIZE_DWORD 3
>> +#define ACPI_ACCESS_SIZE_QWORD 4
>> +
>> struct acpi_resource_gpio {
>> u8 revision_id;
>> u8 connection_type;
>> --
>> 2.7.4
>

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