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From: Bjorn Helgaas <helgaas@kernel.org>
To: Lucas Stach <l.stach@pengutronix.de>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
	Jason Cooper <jason@lakedaemon.net>,
	linux-pci@vger.kernel.org, patchwork-lst@pengutronix.de,
	kernel@pengutronix.de, Bjorn Helgaas <bhelgaas@google.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] PCI: mvebu: change delay after reset to the PCIe spec mandated 100ms
Date: Mon, 30 Jan 2017 14:47:40 -0600	[thread overview]
Message-ID: <20170130204740.GT20550@bhelgaas-glaptop.roam.corp.google.com> (raw)
In-Reply-To: <20170116111142.6866-1-l.stach@pengutronix.de>

On Mon, Jan 16, 2017 at 12:11:42PM +0100, Lucas Stach wrote:
> The current default of 20ms cause some devices, which are slow to initialize,
> to not show up during the bus scanning. Change this to the PCIe spec mandated
> 100ms and document this in the DT binding.
> 
> From PCIe base spec rev 3.0, chapter "6.6.1. Conventional Reset":
> 
> "To allow components to perform internal initialization, system software must
> wait a specified minimum period following the end of a Conventional Reset of
> one or more devices before it is permitted to issue Configuration Requests to
> those devices.
> 
> With a Downstream Port that does not support Link speeds greater than
> 5.0 GT/s, software must wait a minimum of 100 ms before sending a
> Configuration Request to the device immediately below that Port."
> 
> Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
> ---
>  Documentation/devicetree/bindings/pci/mvebu-pci.txt | 3 ++-
>  drivers/pci/host/pci-mvebu.c                        | 2 +-
>  2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/pci/mvebu-pci.txt b/Documentation/devicetree/bindings/pci/mvebu-pci.txt
> index 08c716b2c6b6..2de6f65ecfb1 100644
> --- a/Documentation/devicetree/bindings/pci/mvebu-pci.txt
> +++ b/Documentation/devicetree/bindings/pci/mvebu-pci.txt
> @@ -78,7 +78,8 @@ and the following optional properties:
>    multiple lanes. If this property is not found, we assume that the
>    value is 0.
>  - reset-gpios: optional gpio to PERST#
> -- reset-delay-us: delay in us to wait after reset de-assertion
> +- reset-delay-us: delay in us to wait after reset de-assertion, if not
> +  specified will default to 100ms, as required by the PCIe specification.
>  
>  Example:
>  
> diff --git a/drivers/pci/host/pci-mvebu.c b/drivers/pci/host/pci-mvebu.c
> index 45a89d969700..0c9dd47ce74d 100644
> --- a/drivers/pci/host/pci-mvebu.c
> +++ b/drivers/pci/host/pci-mvebu.c
> @@ -1162,7 +1162,7 @@ static int mvebu_pcie_powerup(struct mvebu_pcie_port *port)
>  		return ret;
>  
>  	if (port->reset_gpio) {
> -		u32 reset_udelay = 20000;
> +		u32 reset_udelay = 100000;

Can we use "PCI_PM_D3COLD_WAIT * 1000" for the initial value to connect it
with other similar cases?

>  
>  		of_property_read_u32(port->dn, "reset-delay-us",
>  				     &reset_udelay);
> -- 
> 2.11.0
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

WARNING: multiple messages have this Message-ID (diff)
From: helgaas@kernel.org (Bjorn Helgaas)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] PCI: mvebu: change delay after reset to the PCIe spec mandated 100ms
Date: Mon, 30 Jan 2017 14:47:40 -0600	[thread overview]
Message-ID: <20170130204740.GT20550@bhelgaas-glaptop.roam.corp.google.com> (raw)
In-Reply-To: <20170116111142.6866-1-l.stach@pengutronix.de>

On Mon, Jan 16, 2017 at 12:11:42PM +0100, Lucas Stach wrote:
> The current default of 20ms cause some devices, which are slow to initialize,
> to not show up during the bus scanning. Change this to the PCIe spec mandated
> 100ms and document this in the DT binding.
> 
> From PCIe base spec rev 3.0, chapter "6.6.1. Conventional Reset":
> 
> "To allow components to perform internal initialization, system software must
> wait a specified minimum period following the end of a Conventional Reset of
> one or more devices before it is permitted to issue Configuration Requests to
> those devices.
> 
> With a Downstream Port that does not support Link speeds greater than
> 5.0 GT/s, software must wait a minimum of 100 ms before sending a
> Configuration Request to the device immediately below that Port."
> 
> Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
> ---
>  Documentation/devicetree/bindings/pci/mvebu-pci.txt | 3 ++-
>  drivers/pci/host/pci-mvebu.c                        | 2 +-
>  2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/pci/mvebu-pci.txt b/Documentation/devicetree/bindings/pci/mvebu-pci.txt
> index 08c716b2c6b6..2de6f65ecfb1 100644
> --- a/Documentation/devicetree/bindings/pci/mvebu-pci.txt
> +++ b/Documentation/devicetree/bindings/pci/mvebu-pci.txt
> @@ -78,7 +78,8 @@ and the following optional properties:
>    multiple lanes. If this property is not found, we assume that the
>    value is 0.
>  - reset-gpios: optional gpio to PERST#
> -- reset-delay-us: delay in us to wait after reset de-assertion
> +- reset-delay-us: delay in us to wait after reset de-assertion, if not
> +  specified will default to 100ms, as required by the PCIe specification.
>  
>  Example:
>  
> diff --git a/drivers/pci/host/pci-mvebu.c b/drivers/pci/host/pci-mvebu.c
> index 45a89d969700..0c9dd47ce74d 100644
> --- a/drivers/pci/host/pci-mvebu.c
> +++ b/drivers/pci/host/pci-mvebu.c
> @@ -1162,7 +1162,7 @@ static int mvebu_pcie_powerup(struct mvebu_pcie_port *port)
>  		return ret;
>  
>  	if (port->reset_gpio) {
> -		u32 reset_udelay = 20000;
> +		u32 reset_udelay = 100000;

Can we use "PCI_PM_D3COLD_WAIT * 1000" for the initial value to connect it
with other similar cases?

>  
>  		of_property_read_u32(port->dn, "reset-delay-us",
>  				     &reset_udelay);
> -- 
> 2.11.0
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  parent reply	other threads:[~2017-01-30 20:47 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-01-16 11:11 [PATCH] PCI: mvebu: change delay after reset to the PCIe spec mandated 100ms Lucas Stach
2017-01-16 11:11 ` Lucas Stach
2017-01-16 11:44 ` Jason Cooper
2017-01-16 11:44   ` Jason Cooper
2017-01-30 20:47 ` Bjorn Helgaas [this message]
2017-01-30 20:47   ` Bjorn Helgaas
2017-01-31 10:27   ` Lucas Stach
2017-01-31 10:27     ` Lucas Stach

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