linux-kernel - [PATCH v13 19/21] PCI: Add PCIE_RESET_CONFIG_DEVICE_WAIT

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Date:   Thu, 14 Dec 2023 15:28:37 +0800
From:   Minda Chen <minda.chen@...rfivetech.com>
To:     Conor Dooley <conor@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Rob Herring <robh+dt@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        "Daire McNamara" <daire.mcnamara@...rochip.com>,
        Emil Renner Berthing <emil.renner.berthing@...onical.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
CC:     <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-riscv@...ts.infradead.org>, <linux-pci@...r.kernel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Mason Huo <mason.huo@...rfivetech.com>,
        Leyfoon Tan <leyfoon.tan@...rfivetech.com>,
        Kevin Xie <kevin.xie@...rfivetech.com>,
        Minda Chen <minda.chen@...rfivetech.com>
Subject: [PATCH v13 19/21] PCI: Add PCIE_RESET_CONFIG_DEVICE_WAIT_MS waiting time value

From: Kevin Xie <kevin.xie@...rfivetech.com>

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 <kevin.xie@...rfivetech.com>
Reviewed-by: Mason Huo <mason.huo@...rfivetech.com>
---
 drivers/pci/pci.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 5ecbcf041179..06f1f1eb878c 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;
 
-- 
2.17.1