[PATCH V4 07/12] PCI/TPH: Add pcie_tph_set_st_entry() to set ST tag

Wei Huang
2024-08-22T20:42:52Z

Add a function to update the device's steering tags. Depending on the
ST table location, the tags will be automatically written into the
device's MSI-X table or into the ST table located in the TPH Extended
Capability space.

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 | 161 ++++++++++++++++++++++++++++++++++++++++
include/linux/pci-tph.h | 5 ++
2 files changed, 166 insertions(+)

diff --git a/drivers/pci/pcie/tph.c b/drivers/pci/pcie/tph.c
index d949930e7e78..82189361a2ee 100644
--- a/drivers/pci/pcie/tph.c
+++ b/drivers/pci/pcie/tph.c
@@ -8,10 +8,24 @@
*/
#include <linux/pci.h>
#include <linux/bitfield.h>
+#include <linux/msi.h>
#include <linux/pci-tph.h>

#include "../pci.h"

+/* Update the TPH Requester Enable field of TPH Control Register */
+static void set_ctrl_reg_req_en(struct pci_dev *pdev, u8 req_type)
+{
+ u32 reg;
+
+ pci_read_config_dword(pdev, pdev->tph_cap + PCI_TPH_CTRL, &reg);
+
+ reg &= ~PCI_TPH_CTRL_REQ_EN_MASK;
+ reg |= FIELD_PREP(PCI_TPH_CTRL_REQ_EN_MASK, req_type);
+
+ pci_write_config_dword(pdev, pdev->tph_cap + PCI_TPH_CTRL, reg);
+}
+
static u8 get_st_modes(struct pci_dev *pdev)
{
u32 reg;
@@ -22,6 +36,37 @@ static u8 get_st_modes(struct pci_dev *pdev)
return reg;
}

+static u32 get_st_table_loc(struct pci_dev *pdev)
+{
+ u32 reg;
+
+ pci_read_config_dword(pdev, pdev->tph_cap + PCI_TPH_CAP, &reg);
+
+ return FIELD_GET(PCI_TPH_CAP_LOC_MASK, reg);
+}
+
+/*
+ * Return the size of ST table. If ST table is not in TPH Requester Extended
+ * Capability space, return 0. Otherwise return the ST Table Size + 1.
+ */
+static u16 get_st_table_size(struct pci_dev *pdev)
+{
+ u32 reg;
+ u32 loc;
+
+ /* Check ST table location first */
+ loc = get_st_table_loc(pdev);
+
+ /* Convert loc to match with PCI_TPH_LOC_* defined in pci_regs.h */
+ loc = FIELD_PREP(PCI_TPH_CAP_LOC_MASK, loc);
+ if (loc != PCI_TPH_LOC_CAP)
+ return 0;
+
+ pci_read_config_dword(pdev, pdev->tph_cap + PCI_TPH_CAP, &reg);
+
+ return FIELD_GET(PCI_TPH_CAP_ST_MASK, reg) + 1;
+}
+
/* Return device's Root Port completer capability */
static u8 get_rp_completer_type(struct pci_dev *pdev)
{
@@ -40,6 +85,122 @@ static u8 get_rp_completer_type(struct pci_dev *pdev)
return FIELD_GET(PCI_EXP_DEVCAP2_TPH_COMP_MASK, reg);
}

+/* Write ST to MSI-X vector control reg - Return 0 if OK, otherwise -errno */
+static int write_tag_to_msix(struct pci_dev *pdev, int msix_idx, u16 tag)
+{
+ struct msi_desc *msi_desc = NULL;
+ void __iomem *vec_ctrl;
+ u32 val, mask;
+ int err = 0;
+
+ msi_lock_descs(&pdev->dev);
+
+ /* Find the msi_desc entry with matching msix_idx */
+ msi_for_each_desc(msi_desc, &pdev->dev, MSI_DESC_ASSOCIATED) {
+ if (msi_desc->msi_index == msix_idx)
+ break;
+ }
+
+ if (!msi_desc) {
+ err = -ENXIO;
+ goto err_out;
+ }
+
+ /* Get the vector control register (offset 0xc) pointed by msix_idx */
+ vec_ctrl = pdev->msix_base + msix_idx * PCI_MSIX_ENTRY_SIZE;
+ vec_ctrl += PCI_MSIX_ENTRY_VECTOR_CTRL;
+
+ val = readl(vec_ctrl);
+ mask = PCI_MSIX_ENTRY_CTRL_ST_LOWER | PCI_MSIX_ENTRY_CTRL_ST_UPPER;
+ val &= ~mask;
+ val |= FIELD_PREP(mask, tag);
+ writel(val, vec_ctrl);
+
+ /* Read back to flush the update */
+ val = readl(vec_ctrl);
+
+err_out:
+ msi_unlock_descs(&pdev->dev);
+ return err;
+}
+
+/* Write tag to ST table - Return 0 if OK, otherwise errno */
+static int write_tag_to_st_table(struct pci_dev *pdev, int index, u16 tag)
+{
+ int st_table_size;
+ int offset;
+
+ /* Check if index is out of bound */
+ st_table_size = get_st_table_size(pdev);
+ if (index >= st_table_size)
+ return -ENXIO;
+
+ offset = pdev->tph_cap + PCI_TPH_BASE_SIZEOF + index * sizeof(u16);
+
+ return pci_write_config_word(pdev, offset, tag);
+}
+
+/**
+ * pcie_tph_set_st_entry() - Set Steering Tag in the ST table entry
+ * @pdev: PCI device
+ * @index: ST table entry index
+ * @tag: Steering Tag to be written
+ *
+ * This function will figure out the proper location of ST table, either in
+ * the MSI-X table or in the TPH Extended Capability space, and write the
+ * Steering Tag into the ST entry pointed by index.
+ *
+ * Returns: 0 if success, otherwise negative value (-errno)
+ */
+int pcie_tph_set_st_entry(struct pci_dev *pdev, unsigned int index, u16 tag)
+{
+ u32 loc;
+ int err = 0;
+
+ if (!pdev->tph_cap)
+ return -EINVAL;
+
+ if (!pdev->tph_enabled)
+ return -EINVAL;
+
+ /* No need to write tag if device is in "No ST Mode" */
+ if (pdev->tph_mode == PCI_TPH_NO_ST_MODE)
+ return 0;
+
+ /* Disable TPH before updating ST to avoid potential instability as
+ * cautioned in PCIe r6.2, sec 6.17.3, "ST Modes of Operation"
+ */
+ set_ctrl_reg_req_en(pdev, PCI_TPH_REQ_DISABLE);
+
+ loc = get_st_table_loc(pdev);
+ /* Convert loc to match with PCI_TPH_LOC_* defined in pci_regs.h */
+ loc = FIELD_PREP(PCI_TPH_CAP_LOC_MASK, loc);
+
+ switch (loc) {
+ case PCI_TPH_LOC_MSIX:
+ err = write_tag_to_msix(pdev, index, tag);
+ break;
+ case PCI_TPH_LOC_CAP:
+ err = write_tag_to_st_table(pdev, index, tag);
+ break;
+ default:
+ err = -EINVAL;
+ }
+
+ if (err) {
+ pcie_disable_tph(pdev);
+ return err;
+ }
+
+ set_ctrl_reg_req_en(pdev, pdev->tph_mode);
+
+ pci_dbg(pdev, "set steering tag: %s table, index=%d, tag=%#04x\n",
+ (loc == PCI_TPH_LOC_MSIX) ? "MSI-X" : "ST", index, tag);
+
+ return 0;
+}
+EXPORT_SYMBOL(pcie_tph_set_st_entry);
+
/**
* pcie_tph_enabled - Check whether TPH is enabled in device
* @pdev: PCI device
diff --git a/include/linux/pci-tph.h b/include/linux/pci-tph.h
index 50e05cdfbc43..a0c93b97090a 100644
--- a/include/linux/pci-tph.h
+++ b/include/linux/pci-tph.h
@@ -10,11 +10,16 @@
#define LINUX_PCI_TPH_H

#ifdef CONFIG_PCIE_TPH
+int pcie_tph_set_st_entry(struct pci_dev *pdev,
+ unsigned int index, u16 tag);
bool pcie_tph_enabled(struct pci_dev *pdev);
void pcie_disable_tph(struct pci_dev *pdev);
int pcie_enable_tph(struct pci_dev *pdev, int mode);
int pcie_tph_modes(struct pci_dev *pdev);
#else
+static inline int pcie_tph_set_st_entry(struct pci_dev *pdev,
+ unsigned int index, u16 tag)
+{ return -EINVAL; }
static inline bool pcie_tph_enabled(struct pci_dev *pdev) { return false; }
static inline void pcie_disable_tph(struct pci_dev *pdev) { }
static inline int pcie_enable_tph(struct pci_dev *pdev, int mode)
--
2.45.1