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>
---
v2:
- Reorder var declaration and use C99 style. (Jonathan)
- Allow >2 ACPI objects in package for future expansion. (Jonathan)
- Check QTG IDs against MAX QTG ID provided by output package. (Jonathan)
---
drivers/cxl/core/Makefile | 1
drivers/cxl/core/acpi.c | 116 +++++++++++++++++++++++++++++++++++++++++++++
drivers/cxl/cxl.h | 16 ++++++
3 files changed, 133 insertions(+)
create mode 100644 drivers/cxl/core/acpi.c
diff --git a/drivers/cxl/core/Makefile b/drivers/cxl/core/Makefile
index 867a8014b462..30d61c8cae22 100644
--- a/drivers/cxl/core/Makefile
+++ b/drivers/cxl/core/Makefile
@@ -13,5 +13,6 @@ 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-$(CONFIG_TRACING) += trace.o
cxl_core-$(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..6eda5cad8d59
--- /dev/null
+++ b/drivers/cxl/core/acpi.c
@@ -0,0 +1,116 @@
+// 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)
+{
+ union acpi_object *out_obj, *out_buf, *pkg;
+ union acpi_object in_buf = {
+ .buffer = {
+ .type = ACPI_TYPE_BUFFER,
+ .pointer = (u8 *)input,
+ .length = sizeof(u32) * 4,
+ },
+ };
+ union acpi_object in_obj = {
+ .package = {
+ .type = ACPI_TYPE_PACKAGE,
+ .count = 1,
+ .elements = &in_buf
+ },
+ };
+ struct qtg_dsm_output *output = NULL;
+ int len, rc, i;
+ u16 *max_qtg;
+
+ 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;
+ }
+
+ /* Check Max QTG ID */
+ pkg = &out_obj->package.elements[0];
+ if (pkg->type != ACPI_TYPE_BUFFER) {
+ rc = -ENXIO;
+ goto err;
+ }
+
+ if (pkg->buffer.length != sizeof(u16)) {
+ rc = -ENXIO;
+ goto err;
+ }
+ max_qtg = (u16 *)pkg->buffer.pointer;
+
+ /* Retrieve QTG IDs package */
+ 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;
+
+ /* It's legal to have 0 QTG entries */
+ if (len == 0)
+ goto out;
+
+ /* Malformed package, not multiple of WORD size */
+ if (len % sizeof(u16)) {
+ rc = -ENXIO;
+ goto out;
+ }
+
+ output = kmalloc(len + sizeof(*output), GFP_KERNEL);
+ if (!output) {
+ rc = -ENOMEM;
+ goto err;
+ }
+
+ output->nr = len / sizeof(u16);
+ memcpy(output->qtg_ids, out_buf->buffer.pointer, len);
+
+ for (i = 0; i < output->nr; i++) {
+ if (output->qtg_ids[i] > *max_qtg)
+ pr_warn("QTG ID %u greater than MAX %u\n",
+ output->qtg_ids[i], *max_qtg);
+ }
+
+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 318aa051f65a..6426c4c22e28 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -7,6 +7,7 @@
#include <linux/libnvdimm.h>
#include <linux/bitfield.h>
#include <linux/bitops.h>
+#include <linux/acpi.h>
#include <linux/log2.h>
#include <linux/list.h>
#include <linux/io.h>
@@ -793,6 +794,21 @@ static inline struct cxl_dax_region *to_cxl_dax_region(struct device *dev)
}
#endif
+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/.
