[PATCH v2] ALSA: hda: Refactor Intel NHLT init

[Cezary Rojewski <cezary.rojewski@intel.com>]

NHLT fetch based on _DSM prevents ACPI table override mechanism from
being utilized. Make use of acpi_get_table to enable it and get rid of
redundant code. In consequence, NHLT can be overridden just like any
other ACPI table, e.g.: DSDT or SSDT.

Change has been verified on all Intel AVS architecture platforms, RVP
and production laptops both.

Change possible due to addition of NHLT signature to the list of
standard ACPI tables:
https://patchwork.kernel.org/patch/11463235/

Override helps not only with debug purposes but also allows user for
table adjustment when one found on their production hardware is invalid.
Shared official NHLT spec is now available to community at:
https://01.org/blogs/intel-smart-sound-technology-audio-dsp

NHLT support for iASL is still ongoing subject but should be available
in nearest future.

Signed-off-by: Cezary Rojewski <cezary.rojewski@intel.com>
---

Changes in v2:
- commit message update, no functional changes

 sound/hda/intel-nhlt.c | 49 +++++++-----------------------------------
 1 file changed, 8 insertions(+), 41 deletions(-)

diff --git a/sound/hda/intel-nhlt.c b/sound/hda/intel-nhlt.c
index 99a23fe7fab9..2f741d2792d8 100644
--- a/sound/hda/intel-nhlt.c
+++ b/sound/hda/intel-nhlt.c
@@ -4,58 +4,25 @@
 #include <linux/acpi.h>
 #include <sound/intel-nhlt.h>
 
-#define NHLT_ACPI_HEADER_SIG	"NHLT"
-
-/* Unique identification for getting NHLT blobs */
-static const guid_t osc_guid =
-	GUID_INIT(0xA69F886E, 0x6CEB, 0x4594,
-		  0xA4, 0x1F, 0x7B, 0x5D, 0xCE, 0x24, 0xC5, 0x53);
-
 struct nhlt_acpi_table *intel_nhlt_init(struct device *dev)
 {
-	acpi_handle handle;
-	union acpi_object *obj;
-	struct nhlt_resource_desc *nhlt_ptr;
-	struct nhlt_acpi_table *nhlt_table = NULL;
-
-	handle = ACPI_HANDLE(dev);
-	if (!handle) {
-		dev_err(dev, "Didn't find ACPI_HANDLE\n");
-		return NULL;
-	}
+	struct nhlt_acpi_table *nhlt;
+	acpi_status status;
 
-	obj = acpi_evaluate_dsm(handle, &osc_guid, 1, 1, NULL);
-
-	if (!obj)
-		return NULL;
-
-	if (obj->type != ACPI_TYPE_BUFFER) {
-		dev_dbg(dev, "No NHLT table found\n");
-		ACPI_FREE(obj);
+	status = acpi_get_table(ACPI_SIG_NHLT, 0,
+				(struct acpi_table_header **)&nhlt);
+	if (ACPI_FAILURE(status)) {
+		dev_warn(dev, "NHLT table not found\n");
 		return NULL;
 	}
 
-	nhlt_ptr = (struct nhlt_resource_desc  *)obj->buffer.pointer;
-	if (nhlt_ptr->length)
-		nhlt_table = (struct nhlt_acpi_table *)
-			memremap(nhlt_ptr->min_addr, nhlt_ptr->length,
-				 MEMREMAP_WB);
-	ACPI_FREE(obj);
-	if (nhlt_table &&
-	    (strncmp(nhlt_table->header.signature,
-		     NHLT_ACPI_HEADER_SIG,
-		     strlen(NHLT_ACPI_HEADER_SIG)) != 0)) {
-		memunmap(nhlt_table);
-		dev_err(dev, "NHLT ACPI header signature incorrect\n");
-		return NULL;
-	}
-	return nhlt_table;
+	return nhlt;
 }
 EXPORT_SYMBOL_GPL(intel_nhlt_init);
 
 void intel_nhlt_free(struct nhlt_acpi_table *nhlt)
 {
-	memunmap((void *)nhlt);
+	acpi_put_table((struct acpi_table_header *)nhlt);
 }
 EXPORT_SYMBOL_GPL(intel_nhlt_free);
 
-- 
2.17.1