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

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Message-ID: <20231227190813.GA1508471@bhelgaas>
Date: Wed, 27 Dec 2023 13:08:13 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Minda Chen <minda.chen@...rfivetech.com>
Cc: 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>,
	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>
Subject: Re: [PATCH v13 19/21] PCI: Add PCIE_RESET_CONFIG_DEVICE_WAIT_MS
 waiting time value

On Thu, Dec 14, 2023 at 03:28:37PM +0800, Minda Chen wrote:
> 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 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
>