[PATCH V2 6/9] PCI/TPH: Retrieve steering tag from ACPI _DSM

Wei Huang
2024-05-31T21:40:32Z

According to PCI SIG ECN, calling the _DSM firmware method for a given
CPU_UID returns the steering tags for different types of memory
(volatile, non-volatile). These tags are supposed to be used in ST
table entry for optimal results.

Co-developed-by: Eric Van Tassell <Eric.VanTassell@amd.com>
Signed-off-by: Eric Van Tassell <Eric.VanTassell@amd.com>
Signed-off-by: Wei Huang <wei.huang2@amd.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
Reviewed-by: Andy Gospodarek <andrew.gospodarek@broadcom.com>
---
drivers/pci/pcie/tph.c | 103 +++++++++++++++++++++++++++++++++++++++-
include/linux/pci-tph.h | 34 +++++++++++++
2 files changed, 136 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/pcie/tph.c b/drivers/pci/pcie/tph.c
index 320b99c60365..425935a14b62 100644
--- a/drivers/pci/pcie/tph.c
+++ b/drivers/pci/pcie/tph.c
@@ -158,6 +158,98 @@ static int tph_get_table_location(struct pci_dev *dev, u8 *loc_out)
return 0;
}

+static u16 tph_extract_tag(enum tph_mem_type mem_type, u8 req_type,
+ union st_info *st_tag)
+{
+ switch (req_type) {
+ case PCI_TPH_REQ_TPH_ONLY: /* 8 bit tags */
+ switch (mem_type) {
+ case TPH_MEM_TYPE_VM:
+ if (st_tag->vm_st_valid)
+ return st_tag->vm_st;
+ break;
+ case TPH_MEM_TYPE_PM:
+ if (st_tag->pm_st_valid)
+ return st_tag->pm_st;
+ break;
+ }
+ break;
+ case PCI_TPH_REQ_EXT_TPH: /* 16 bit tags */
+ switch (mem_type) {
+ case TPH_MEM_TYPE_VM:
+ if (st_tag->vm_xst_valid)
+ return st_tag->vm_xst;
+ break;
+ case TPH_MEM_TYPE_PM:
+ if (st_tag->pm_xst_valid)
+ return st_tag->pm_xst;
+ break;
+ }
+ break;
+ default:
+ pr_err("invalid steering tag in ACPI _DSM\n");
+ return 0;
+ }
+
+ return 0;
+}
+
+#define MIN_ST_DSM_REV 7
+#define ST_DSM_FUNC_INDEX 0xf
+static bool invoke_dsm(acpi_handle handle, u32 cpu_uid, u8 ph,
+ u8 target_type, bool cache_ref_valid,
+ u64 cache_ref, union st_info *st_out)
+{
+ union acpi_object in_obj, in_buf[3], *out_obj;
+
+ in_buf[0].integer.type = ACPI_TYPE_INTEGER;
+ in_buf[0].integer.value = 0; /* 0 => processor cache steering tags */
+
+ in_buf[1].integer.type = ACPI_TYPE_INTEGER;
+ in_buf[1].integer.value = cpu_uid;
+
+ in_buf[2].integer.type = ACPI_TYPE_INTEGER;
+ in_buf[2].integer.value = ph & 3;
+ in_buf[2].integer.value |= (target_type & 1) << 2;
+ in_buf[2].integer.value |= (cache_ref_valid & 1) << 3;
+ in_buf[2].integer.value |= (cache_ref << 32);
+
+ in_obj.type = ACPI_TYPE_PACKAGE;
+ in_obj.package.count = ARRAY_SIZE(in_buf);
+ in_obj.package.elements = in_buf;
+
+ out_obj = acpi_evaluate_dsm(handle, &pci_acpi_dsm_guid, MIN_ST_DSM_REV,
+ ST_DSM_FUNC_INDEX, &in_obj);
+
+ if (!out_obj)
+ return false;
+
+ if (out_obj->type != ACPI_TYPE_BUFFER) {
+ pr_err("invalid return type %d from TPH _DSM\n",
+ out_obj->type);
+ ACPI_FREE(out_obj);
+ return false;
+ }
+
+ st_out->value = *((u64 *)(out_obj->buffer.pointer));
+
+ ACPI_FREE(out_obj);
+
+ return true;
+}
+
+static acpi_handle root_complex_acpi_handle(struct pci_dev *dev)
+{
+ struct pci_dev *root_port;
+
+ root_port = pcie_find_root_port(dev);
+
+ if (!root_port || !root_port->bus || !root_port->bus->bridge)
+ return NULL;
+
+ return ACPI_HANDLE(root_port->bus->bridge);
+}
+
static bool msix_nr_in_bounds(struct pci_dev *dev, int msix_nr)
{
u16 tbl_sz;
@@ -441,7 +533,16 @@ bool pcie_tph_get_st(struct pci_dev *dev, unsigned int cpu,
enum tph_mem_type mem_type, u8 req_type,
u16 *tag)
{
- *tag = 0;
+ union st_info info;
+
+ if (!invoke_dsm(root_complex_acpi_handle(dev), cpu, 0, 0, false, 0,
+ &info)) {
+ *tag = 0;
+ return false;
+ }
+
+ *tag = tph_extract_tag(mem_type, req_type, &info);
+ pr_debug("%s: cpu=%d tag=%d\n", __func__, cpu, *tag);

return true;
}
diff --git a/include/linux/pci-tph.h b/include/linux/pci-tph.h
index 4fbd1e2fd98c..79533c6254c2 100644
--- a/include/linux/pci-tph.h
+++ b/include/linux/pci-tph.h
@@ -14,6 +14,40 @@ enum tph_mem_type {
TPH_MEM_TYPE_PM /* persistent memory type */
};

+/*
+ * The st_info struct defines the steering tag returned by the firmware _DSM
+ * method defined in PCI SIG ECN. The specification is available at:
+ * https://members.pcisig.com/wg/PCI-SIG/document/15470.
+
+ * @vm_st_valid: 8 bit tag for volatile memory is valid
+ * @vm_xst_valid: 16 bit tag for volatile memory is valid
+ * @vm_ignore: 1 => was and will be ignored, 0 => ph should be supplied
+ * @vm_st: 8 bit steering tag for volatile mem
+ * @vm_xst: 16 bit steering tag for volatile mem
+ * @pm_st_valid: 8 bit tag for persistent memory is valid
+ * @pm_xst_valid: 16 bit tag for persistent memory is valid
+ * @pm_ignore: 1 => was and will be ignore, 0 => ph should be supplied
+ * @pm_st: 8 bit steering tag for persistent mem
+ * @pm_xst: 16 bit steering tag for persistent mem
+ */
+union st_info {
+ struct {
+ u64 vm_st_valid:1,
+ vm_xst_valid:1,
+ vm_ph_ignore:1,
+ rsvd1:5,
+ vm_st:8,
+ vm_xst:16,
+ pm_st_valid:1,
+ pm_xst_valid:1,
+ pm_ph_ignore:1,
+ rsvd2:5,
+ pm_st:8,
+ pm_xst:16;
+ };
+ u64 value;
+};
+
#ifdef CONFIG_PCIE_TPH
int pcie_tph_disable(struct pci_dev *dev);
int tph_set_dev_nostmode(struct pci_dev *dev);
--
2.44.0