linux-kernel - [PATCH v16 20/22] PCI: Add PCIE_RESET_CONFIG_DEVICE_WAIT

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Message-Id: <20240328091835.14797-21-minda.chen@starfivetech.com>
Date: Thu, 28 Mar 2024 17:18:33 +0800
From: Minda Chen <minda.chen@...rfivetech.com>
To: Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Conor Dooley <conor@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Rob Herring <robh+dt@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	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 v16 20/22] 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>
Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>
---
 drivers/pci/pci.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 17fed1846847..6fa59d6aa063 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