[v15,20/23] PCI: Add PCIE_RESET_CONFIG_DEVICE_WAIT_MS waiting time value

Commit Message

Minda Chen Feb. 18, 2024, 10:19 a.m. UTC

From: Kevin Xie <[e-mail]>

Add the PCIE_RESET_CONFIG_DEVICE_WAIT_MS macro to define the minimum
waiting time between exit from a conventional reset and sending the
first configuration request to the device.

As described in PCI base specification r6.0, section 6.6.1 <Conventional
Reset>, there are two different use cases of the value:

   - "With a Downstream Port that does not support Link speeds greater
     than 5.0 GT/s, software must wait a minimum of 100 ms following exit
     from a Conventional Reset before sending a Configuration Request to
     the device immediately below that Port."

   - "With a Downstream Port that supports Link speeds greater than
     5.0 GT/s, software must wait a minimum of 100 ms after Link training
     completes before sending a Configuration Request to the device
     immediately below that Port."

Signed-off-by: Kevin Xie <[e-mail]>
Reviewed-by: Mason Huo <[e-mail]>
Acked-by: Bjorn Helgaas <[e-mail]>
---
 drivers/pci/pci.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

Patch

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index e9750b1b19ba..06d76439bcac 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -22,6 +22,22 @@ 
  */
 #define PCIE_PME_TO_L2_TIMEOUT_US	10000
 
+/*
+ * As described in PCI base specification r6.0, section 6.6.1 <Conventional
+ * Reset>, there are two different use cases of the value:
+ *
+ * - "With a Downstream Port that does not support Link speeds greater
+ *    than 5.0 GT/s, software must wait a minimum of 100 ms following exit
+ *    from a Conventional Reset before sending a Configuration Request to
+ *    the device immediately below that Port."
+ *
+ * - "With a Downstream Port that supports Link speeds greater than
+ *    5.0 GT/s, software must wait a minimum of 100 ms after Link training
+ *    completes before sending a Configuration Request to the device
+ *    immediately below that Port."
+ */
+#define PCIE_RESET_CONFIG_DEVICE_WAIT_MS	100
+
 extern const unsigned char pcie_link_speed[];
 extern bool pci_early_dump;