CXL spec v3.0 9.17.3 CXL Root Device Specific Methods (_DSM)
Add support to retrieve QTG ID via ACPI _DSM call. The _DSM call requires
an input of an ACPI package with 4 dwords (read latency, write latency,
read bandwidth, write bandwidth). The call returns a package with 1 WORD
that provides the max supported QTG ID and a package that may contain 0 or
more WORDs as the recommended QTG IDs in the recommended order.
Signed-off-by: Dave Jiang <dave.jiang@xxxxxxxxx>
---
drivers/cxl/core/Makefile | 1
drivers/cxl/core/acpi.c | 99 +++++++++++++++++++++++++++++++++++++++++++++
drivers/cxl/cxl.h | 15 +++++++
3 files changed, 115 insertions(+)
create mode 100644 drivers/cxl/core/acpi.c
diff --git a/drivers/cxl/core/Makefile b/drivers/cxl/core/Makefile
index 438ce27faf77..11ccc2016ab7 100644
--- a/drivers/cxl/core/Makefile
+++ b/drivers/cxl/core/Makefile
@@ -11,4 +11,5 @@ cxl_core-y += mbox.o
cxl_core-y += pci.o
cxl_core-y += hdm.o
cxl_core-y += cdat.o
+cxl_core-y += acpi.o
cxl_core-$(CONFIG_CXL_REGION) += region.o
diff --git a/drivers/cxl/core/acpi.c b/drivers/cxl/core/acpi.c
new file mode 100644
index 000000000000..86dc6c9c1f24
--- /dev/null
+++ b/drivers/cxl/core/acpi.c
@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright(c) 2022 Intel Corporation. All rights reserved. */
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/acpi.h>
+#include <linux/pci.h>
+#include <asm/div64.h>
+#include "cxlpci.h"
+#include "cxl.h"
+
+const guid_t acpi_cxl_qtg_id_guid =
+ GUID_INIT(0xF365F9A6, 0xA7DE, 0x4071,
+ 0xA6, 0x6A, 0xB4, 0x0C, 0x0B, 0x4F, 0x8E, 0x52);
+
+/**
+ * cxl_acpi_evaluate_qtg_dsm - Retrieve QTG ids via ACPI _DSM
+ * @handle: ACPI handle
+ * @input: bandwidth and latency data
+ *
+ * Issue QTG _DSM with accompanied bandwidth and latency data in order to get
+ * the QTG IDs that falls within the performance data.
+ */
+struct qtg_dsm_output *cxl_acpi_evaluate_qtg_dsm(acpi_handle handle,
+ struct qtg_dsm_input *input)
+{
+ struct qtg_dsm_output *output;
+ union acpi_object *out_obj, *out_buf, *pkg, in_buf, in_obj;
+ int len;
+ int rc;
+
+ in_obj.type = ACPI_TYPE_PACKAGE;
+ in_obj.package.count = 1;
+ in_obj.package.elements = &in_buf;
+ in_buf.type = ACPI_TYPE_BUFFER;
+ in_buf.buffer.pointer = (u8 *)input;
+ in_buf.buffer.length = sizeof(u32) * 4;
+
+ out_obj = acpi_evaluate_dsm(handle, &acpi_cxl_qtg_id_guid, 1, 1, &in_obj);
+ if (!out_obj)
+ return ERR_PTR(-ENXIO);
+
+ if (out_obj->type != ACPI_TYPE_PACKAGE) {
+ rc = -ENXIO;
+ goto err;
+ }
+
+ /*
+ * CXL spec v3.0 9.17.3.1
+ * There should be 2 elements in the package. 1 WORD for max QTG ID supported
+ * by the platform, and the other a package of recommended QTGs
+ */
+ if (out_obj->package.count != 2) {
+ rc = -ENXIO;
+ goto err;
+ }
+
+ pkg = &out_obj->package.elements[1];
+ if (pkg->type != ACPI_TYPE_PACKAGE) {
+ rc = -ENXIO;
+ goto err;
+ }
+
+ out_buf = &pkg->package.elements[0];
+ if (out_buf->type != ACPI_TYPE_BUFFER) {
+ rc = -ENXIO;
+ goto err;
+ }
+
+ len = out_buf->buffer.length;
+ output = kmalloc(len + sizeof(*output), GFP_KERNEL);
+ if (!output) {
+ rc = -ENOMEM;
+ goto err;
+ }
+
+ /* It's legal to have 0 QTG entries */
+ if (len == 0) {
+ output->nr = 0;
+ goto out;
+ }
+
+ /* Malformed package, not multiple of WORD size */
+ if (len % sizeof(u16)) {
+ rc = -ENXIO;
+ goto out;
+ }
+
+ output->nr = len / sizeof(u16);
+ memcpy(output->qtg_ids, out_buf->buffer.pointer, len);
+out:
+ ACPI_FREE(out_obj);
+ return output;
+
+err:
+ ACPI_FREE(out_obj);
+ return ERR_PTR(rc);
+}
+EXPORT_SYMBOL_NS_GPL(cxl_acpi_evaluate_qtg_dsm, CXL);
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 849b22236f1d..e70df07f9b4b 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -719,6 +719,21 @@ int cdat_table_parse_dslbis(void *table, cdat_tbl_entry_handler handler,
int cxl_dsmas_parse_entry(struct acpi_cdat_header *header, void *arg);
int cxl_dslbis_parse_entry(struct acpi_cdat_header *header, void *arg);
+struct qtg_dsm_input {
+ u32 rd_lat;
+ u32 wr_lat;
+ u32 rd_bw;
+ u32 wr_bw;
+};
+
+struct qtg_dsm_output {
+ int nr;
+ u16 qtg_ids[];
+};
+
+struct qtg_dsm_output *cxl_acpi_evaluate_qtg_dsm(acpi_handle handle,
+ struct qtg_dsm_input *input);
+
/*
* Unit test builds overrides this to __weak, find the 'strong' version
* of these symbols in tools/testing/cxl/.
