[PATCH V4 04/12] PCI/TPH: Add pcie_enable_tph() to enable TPH

Wei Huang
2024-08-22T20:42:18Z

Allow drivers to enable TPH support using a specific ST mode. It checks
whether the mode is actually supported by the device before enabling.
Additionally determines what types of requests, TPH (8-bit) or Extended
TPH (16-bit), can be issued by the device based on the device's TPH
Requester capability and its Root Port's Completer capability.

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 | 92 +++++++++++++++++++++++++++++++++++++++++
include/linux/pci-tph.h | 3 ++
include/linux/pci.h | 3 ++
3 files changed, 98 insertions(+)

diff --git a/drivers/pci/pcie/tph.c b/drivers/pci/pcie/tph.c
index a28dced3097d..14ad8c5e895c 100644
--- a/drivers/pci/pcie/tph.c
+++ b/drivers/pci/pcie/tph.c
@@ -7,6 +7,7 @@
* Wei Huang <wei.huang2@amd.com>
*/
#include <linux/pci.h>
+#include <linux/bitfield.h>
#include <linux/pci-tph.h>

#include "../pci.h"
@@ -21,6 +22,97 @@ static u8 get_st_modes(struct pci_dev *pdev)
return reg;
}

+/* Return device's Root Port completer capability */
+static u8 get_rp_completer_type(struct pci_dev *pdev)
+{
+ struct pci_dev *rp;
+ u32 reg;
+ int ret;
+
+ rp = pcie_find_root_port(pdev);
+ if (!rp)
+ return 0;
+
+ ret = pcie_capability_read_dword(rp, PCI_EXP_DEVCAP2, &reg);
+ if (ret)
+ return 0;
+
+ return FIELD_GET(PCI_EXP_DEVCAP2_TPH_COMP_MASK, reg);
+}
+
+/**
+ * pcie_enable_tph - Enable TPH support for device using a specific ST mode
+ * @pdev: PCI device
+ * @mode: ST mode to enable, as returned by pcie_tph_modes()
+ *
+ * Checks whether the mode is actually supported by the device before enabling
+ * and returns an error if not. Additionally determines what types of requests,
+ * TPH or extended TPH, can be issued by the device based on its TPH requester
+ * capability and the Root Port's completer capability.
+ *
+ * Return: 0 on success, otherwise negative value (-errno)
+ */
+int pcie_enable_tph(struct pci_dev *pdev, int mode)
+{
+ u32 reg;
+ u8 dev_modes;
+ u8 rp_req_type;
+
+ if (!pdev->tph_cap)
+ return -EINVAL;
+
+ if (pdev->tph_enabled)
+ return -EBUSY;
+
+ /* Check ST mode comptability */
+ dev_modes = get_st_modes(pdev);
+ if (!(mode & dev_modes))
+ return -EINVAL;
+
+ /* Select a supported mode */
+ switch (mode) {
+ case PCI_TPH_CAP_INT_VEC:
+ pdev->tph_mode = PCI_TPH_INT_VEC_MODE;
+ break;
+ case PCI_TPH_CAP_DEV_SPEC:
+ pdev->tph_mode = PCI_TPH_DEV_SPEC_MODE;
+ break;
+ case PCI_TPH_CAP_NO_ST:
+ pdev->tph_mode = PCI_TPH_NO_ST_MODE;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ /* Get req_type supported by device and its Root Port */
+ reg = pci_read_config_dword(pdev, pdev->tph_cap + PCI_TPH_CAP, &reg);
+ if (FIELD_GET(PCI_TPH_CAP_EXT_TPH, reg))
+ pdev->tph_req_type = PCI_TPH_REQ_EXT_TPH;
+ else
+ pdev->tph_req_type = PCI_TPH_REQ_TPH_ONLY;
+
+ rp_req_type = get_rp_completer_type(pdev);
+
+ /* Final req_type is the smallest value of two */
+ pdev->tph_req_type = min(pdev->tph_req_type, rp_req_type);
+
+ /* Write them into TPH control register */
+ pci_read_config_dword(pdev, pdev->tph_cap + PCI_TPH_CTRL, &reg);
+
+ reg &= ~PCI_TPH_CTRL_MODE_SEL_MASK;
+ reg |= FIELD_PREP(PCI_TPH_CTRL_MODE_SEL_MASK, pdev->tph_mode);
+
+ reg &= ~PCI_TPH_CTRL_REQ_EN_MASK;
+ reg |= FIELD_PREP(PCI_TPH_CTRL_REQ_EN_MASK, pdev->tph_req_type);
+
+ pci_write_config_dword(pdev, pdev->tph_cap + PCI_TPH_CTRL, reg);
+
+ pdev->tph_enabled = 1;
+
+ return 0;
+}
+EXPORT_SYMBOL(pcie_enable_tph);
+
/**
* pcie_tph_modes - Get the ST modes supported by device
* @pdev: PCI device
diff --git a/include/linux/pci-tph.h b/include/linux/pci-tph.h
index fa378afe9c7e..cdf561076484 100644
--- a/include/linux/pci-tph.h
+++ b/include/linux/pci-tph.h
@@ -10,8 +10,11 @@
#define LINUX_PCI_TPH_H

#ifdef CONFIG_PCIE_TPH
+int pcie_enable_tph(struct pci_dev *pdev, int mode);
int pcie_tph_modes(struct pci_dev *pdev);
#else
+static inline int pcie_enable_tph(struct pci_dev *pdev, int mode)
+{ return -EINVAL; }
static inline int pcie_tph_modes(struct pci_dev *pdev) { return 0; }
#endif

diff --git a/include/linux/pci.h b/include/linux/pci.h
index c59e7ecab491..6f05deb6a0bf 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -433,6 +433,7 @@ struct pci_dev {
unsigned int ats_enabled:1; /* Address Translation Svc */
unsigned int pasid_enabled:1; /* Process Address Space ID */
unsigned int pri_enabled:1; /* Page Request Interface */
+ unsigned int tph_enabled:1; /* TLP Processing Hints */
unsigned int is_managed:1; /* Managed via devres */
unsigned int is_msi_managed:1; /* MSI release via devres installed */
unsigned int needs_freset:1; /* Requires fundamental reset */
@@ -533,6 +534,8 @@ struct pci_dev {

#ifdef CONFIG_PCIE_TPH
u16 tph_cap; /* TPH capability offset */
+ u8 tph_mode; /* TPH mode */
+ u8 tph_req_type; /* TPH requester type */
#endif
};

--
2.45.1