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From:   Minda Chen <minda.chen@starfivetech.com>
To:     Conor Dooley <conor@kernel.org>,
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        Rob Herring <robh+dt@kernel.org>,
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        "Daire McNamara" <daire.mcnamara@microchip.com>,
        Emil Renner Berthing <emil.renner.berthing@canonical.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>
CC:     <devicetree@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-riscv@lists.infradead.org>, <linux-pci@vger.kernel.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Mason Huo <mason.huo@starfivetech.com>,
        Leyfoon Tan <leyfoon.tan@starfivetech.com>,
        Kevin Xie <kevin.xie@starfivetech.com>,
        Minda Chen <minda.chen@starfivetech.com>
Subject: [PATCH v13 19/21] PCI: Add PCIE_RESET_CONFIG_DEVICE_WAIT_MS waiting time value
Date:   Thu, 14 Dec 2023 15:28:37 +0800
Message-ID: <20231214072839.2367-20-minda.chen@starfivetech.com>
In-Reply-To: <20231214072839.2367-1-minda.chen@starfivetech.com>
References: <20231214072839.2367-1-minda.chen@starfivetech.com>
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From: Kevin Xie <kevin.xie@starfivetech.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@starfivetech.com>
Reviewed-by: Mason Huo <mason.huo@starfivetech.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