Re: [PATCH V5 1/5] PCI: Add TLP Processing Hints (TPH) support

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On 9/23/24 21:27, Wei Huang wrote:


On 9/23/24 7:07 AM, Alejandro Lucero Palau wrote:


...

+/**
+ * pcie_enable_tph - Enable TPH support for device using a specific ST mode
+ * @pdev: PCI device
+ * @mode: ST mode to enable. Current supported modes include:
+ *
+ *   - PCI_TPH_ST_NS_MODE: NO ST Mode
+ *   - PCI_TPH_ST_IV_MODE: Interrupt Vector Mode
+ *   - PCI_TPH_ST_DS_MODE: Device Specific Mode
+ *
+ * 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;
+
+    /* Honor "notph" kernel parameter */
+    if (pci_tph_disabled)
+        return -EINVAL;
+
+    if (!pdev->tph_cap)
+        return -EINVAL;
+
+    if (pdev->tph_enabled)
+        return -EBUSY;
+
+    /* Sanitize and check ST mode comptability */
+    mode &= PCI_TPH_CTRL_MODE_SEL_MASK;
+    dev_modes = get_st_modes(pdev);
+    if (!((1 << mode) & dev_modes))


This is wrong. The mode definition is about the bit on and not about bit
position. You got this right in v4 ...

This code is correct. In V5, I changed the "mode" parameter to the following values, as defined in TPH Ctrl register. These values are defined as bit positions:

PCI_TPH_ST_NS_MODE: NO ST Mode
PCI_TPH_ST_IV_MODE: Interrupt Vector Mode
PCI_TPH_ST_DS_MODE: Device Specific Mode


OK. I found the issue. I was using PCI_TPH_CAP_ST_DS for the mode instead of PCI_TPH_ST_DS_MODE.

That change confused me.

Apologies.


In V4, "mode" is defined as masks of TPH Cap register. I felt that V5 looks more straightforward:

V4: pcie_enable_tph(dev, PCI_TPH_CAP_ST_IV)
vs.
V5: pcie_enable_tph(dev, PCI_TPH_ST_IV_MODE)



+        return -EINVAL;





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