ACPI: PCC: Implement OperationRegion handler for the PCC Type 3 subtype

PCC OpRegion provides a mechanism to communicate with the platform
directly from the AML. PCCT provides the list of PCC channel available
in the platform, a subset or all of them can be used in PCC Opregion.

This patch registers the PCC OpRegion handler before ACPI tables are
loaded. This relies on the special context data passed to identify and
set up the PCC channel before the OpRegion handler is executed for the
first time.

Typical PCC Opregion declaration looks like this:

OperationRegion (PFRM, PCC, 2, 0x74)
Field (PFRM, ByteAcc, NoLock, Preserve)
{
    SIGN,   32,
    FLGS,   32,
    LEN,    32,
    CMD,    32,
    DATA,   800
}

It contains four named double words followed by 100 bytes of buffer
names DATA.

ASL can fill out the buffer something like:

    /* Create global or local buffer */
    Name (BUFF, Buffer (0x0C){})
    /* Create double word fields over the buffer */
    CreateDWordField (BUFF, 0x0, WD0)
    CreateDWordField (BUFF, 0x04, WD1)
    CreateDWordField (BUFF, 0x08, WD2)

    /* Fill the named fields */
    WD0 = 0x50434300
    SIGN = BUFF
    WD0 = 1
    FLGS = BUFF
    WD0 = 0x10
    LEN = BUFF

    /* Fill the payload in the DATA buffer */
    WD0 = 0
    WD1 = 0x08
    WD2 = 0
    DATA = BUFF

    /* Write to CMD field to trigger handler */
    WD0 = 0x4404
    CMD = BUFF

This buffer is received by acpi_pcc_opregion_space_handler. This
handler will fetch the complete buffer via internal_pcc_buffer.

The setup handler will receive the special PCC context data which will
contain the PCC channel index which used to set up the channel. The
buffer pointer and length is saved in region context which is then used
in the handler.

(kernel test robot: Build failure with CONFIG_ACPI_DEBUGGER)
Link: https://lore.kernel.org/r/202201041539.feAV0l27-lkp@intel.com
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index b28f8790192a..93eaba2485e3 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -1389,6 +1389,12 @@ static inline int find_acpi_cpu_cache_topology(unsigned int cpu, int level)
 }
 #endif
 
+#ifdef CONFIG_ACPI_PCC
+void acpi_init_pcc(void);
+#else
+static inline void acpi_init_pcc(void) { }
+#endif
+
 #ifdef CONFIG_ACPI
 extern void acpi_device_notify(struct device *dev);
 extern void acpi_device_notify_remove(struct device *dev);