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From: Bjorn Helgaas <helgaas@kernel.org>
To: Manikanta Maddireddy <mmaddireddy@nvidia.com>
Cc: thierry.reding@gmail.com, robh+dt@kernel.org,
	mark.rutland@arm.com, jonathanh@nvidia.com,
	lorenzo.pieralisi@arm.com, vidyas@nvidia.com,
	linux-tegra@vger.kernel.org, linux-pci@vger.kernel.org,
	devicetree@vger.kernel.org
Subject: Re: [PATCH 22/30] PCI: tegra: Access endpoint config only if PCIe link is up
Date: Thu, 11 Apr 2019 15:15:35 -0500
Message-ID: <20190411201535.GS256045@google.com> (raw)
In-Reply-To: <20190411170355.6882-23-mmaddireddy@nvidia.com>

On Thu, Apr 11, 2019 at 10:33:47PM +0530, Manikanta Maddireddy wrote:
> Add PCIe link up check in config read and write callback functions
> before accessing endpoint config registers.
> 
> Signed-off-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
> ---
>  drivers/pci/controller/pci-tegra.c | 38 ++++++++++++++++++++++++++++++
>  1 file changed, 38 insertions(+)
> 
> diff --git a/drivers/pci/controller/pci-tegra.c b/drivers/pci/controller/pci-tegra.c
> index d08a63132c77..c050687020f0 100644
> --- a/drivers/pci/controller/pci-tegra.c
> +++ b/drivers/pci/controller/pci-tegra.c
> @@ -426,6 +426,14 @@ static inline u32 pads_readl(struct tegra_pcie *pcie, unsigned long offset)
>  	return readl(pcie->pads + offset);
>  }
>  
> +static bool tegra_pcie_link_status(struct tegra_pcie_port *port)

Most drivers call this *_pcie_link_up().  It would be better if tegra
followed that convention.

> +{
> +	u32 value;
> +
> +	value = readl(port->base + RP_LINK_CONTROL_STATUS);
> +	return !!(value & RP_LINK_CONTROL_STATUS_DL_LINK_ACTIVE);
> +}
> +
>  /*
>   * The configuration space mapping on Tegra is somewhat similar to the ECAM
>   * defined by PCIe. However it deviates a bit in how the 4 bits for extended
> @@ -491,20 +499,50 @@ static void __iomem *tegra_pcie_map_bus(struct pci_bus *bus,
>  static int tegra_pcie_config_read(struct pci_bus *bus, unsigned int devfn,
>  				  int where, int size, u32 *value)
>  {
> +	struct tegra_pcie *pcie = bus->sysdata;
> +	struct pci_dev *bridge;
> +	struct tegra_pcie_port *port;
> +
>  	if (bus->number == 0)
>  		return pci_generic_config_read32(bus, devfn, where, size,
>  						 value);
>  
> +	bridge = pcie_find_root_port(bus->self);
> +
> +	list_for_each_entry(port, &pcie->ports, list)
> +		if (port->index + 1 == PCI_SLOT(bridge->devfn))
> +			break;
> +
> +	/* If there is no link, then there is no device */
> +	if (!tegra_pcie_link_status(port)) {

This is racy and you should avoid it if possible.  The link could go down
between calling tegra_pcie_link_status() and issuing the config read/write.

If your driver is to be reliable, it must be able to handle any bad
consequence of issuing that config read/write anyway, so I think it's
better if it doesn't even bother checking whether the link is up.

> +		*value = 0xffffffff;
> +		return PCIBIOS_DEVICE_NOT_FOUND;
> +	}
> +
>  	return pci_generic_config_read(bus, devfn, where, size, value);
>  }
>  
>  static int tegra_pcie_config_write(struct pci_bus *bus, unsigned int devfn,
>  				   int where, int size, u32 value)
>  {
> +	struct tegra_pcie *pcie = bus->sysdata;
> +	struct tegra_pcie_port *port;
> +	struct pci_dev *bridge;
> +
>  	if (bus->number == 0)
>  		return pci_generic_config_write32(bus, devfn, where, size,
>  						  value);
>  
> +	bridge = pcie_find_root_port(bus->self);
> +
> +	list_for_each_entry(port, &pcie->ports, list)
> +		if (port->index + 1 == PCI_SLOT(bridge->devfn))
> +			break;
> +
> +	/* If there is no link, then there is no device */
> +	if (!tegra_pcie_link_status(port))
> +		return PCIBIOS_DEVICE_NOT_FOUND;
> +
>  	return pci_generic_config_write(bus, devfn, where, size, value);
>  }
>  
> -- 
> 2.17.1
> 

  reply index

Thread overview: 106+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-11 17:03 [PATCH 00/30] Enable Tegra PCIe root port features Manikanta Maddireddy
2019-04-11 17:03 ` [PATCH 01/30] soc/tegra: pmc: Export tegra_powergate_power_on() Manikanta Maddireddy
2019-04-11 17:03 ` [PATCH 02/30] PCI: tegra: Fix PCIe host power up sequence Manikanta Maddireddy
2019-04-15 11:01   ` Thierry Reding
2019-04-15 14:11     ` Manikanta Maddireddy
2019-04-15 14:30       ` Thierry Reding
2019-04-15 18:14         ` Manikanta Maddireddy
2019-04-11 17:03 ` [PATCH 03/30] PCI: tegra: Move REFCLK pad settings out of phy_power_on() Manikanta Maddireddy
2019-04-15 11:06   ` Thierry Reding
2019-04-15 14:20     ` Manikanta Maddireddy
2019-04-11 17:03 ` [PATCH 04/30] PCI: tegra: Add PCIe Gen2 link speed support Manikanta Maddireddy
2019-04-15 11:21   ` Thierry Reding
2019-04-15 14:47     ` Manikanta Maddireddy
2019-04-15 15:36       ` Thierry Reding
2019-04-15 15:53         ` Manikanta Maddireddy
2019-04-11 17:03 ` [PATCH 05/30] PCI: tegra: Advertise PCIe Advanced Error Reporting (AER) capability Manikanta Maddireddy
2019-04-15 11:23   ` Thierry Reding
2019-04-15 14:49     ` Manikanta Maddireddy
2019-04-11 17:03 ` [PATCH 06/30] PCI: tegra: Program UPHY electrical settings for Tegra210 Manikanta Maddireddy
2019-04-15 11:29   ` Thierry Reding
2019-04-15 14:55     ` Manikanta Maddireddy
2019-04-15 15:38       ` Thierry Reding
2019-04-11 17:03 ` [PATCH 07/30] PCI: tegra: Enable opportunistic update FC and ACK Manikanta Maddireddy
2019-04-15 11:30   ` Thierry Reding
2019-04-11 17:03 ` [PATCH 08/30] PCI: tegra: Disable AFI dynamic clock gating Manikanta Maddireddy
2019-04-15 11:32   ` Thierry Reding
2019-04-11 17:03 ` [PATCH 09/30] PCI: tegra: Process pending DLL transactions before entering L1 or L2 Manikanta Maddireddy
2019-04-15 11:33   ` Thierry Reding
2019-04-11 17:03 ` [PATCH 10/30] PCI: tegra: Enable PCIe xclk clock clamping Manikanta Maddireddy
2019-04-15 11:37   ` Thierry Reding
2019-04-15 14:58     ` Manikanta Maddireddy
2019-04-11 17:03 ` [PATCH 11/30] PCI: tegra: Increase the deskew retry time Manikanta Maddireddy
2019-04-15 11:39   ` Thierry Reding
2019-04-15 14:58     ` Manikanta Maddireddy
2019-04-11 17:03 ` [PATCH 12/30] PCI: tegra: Add SW fixup for RAW violations Manikanta Maddireddy
2019-04-11 20:01   ` Bjorn Helgaas
2019-04-12  5:59     ` Manikanta Maddireddy
2019-04-15 11:41       ` Thierry Reding
2019-04-15 11:45   ` Thierry Reding
2019-04-15 15:02     ` Manikanta Maddireddy
2019-04-11 17:03 ` [PATCH 13/30] PCI: tegra: Update flow control threshold in Tegra210 Manikanta Maddireddy
2019-04-15 11:47   ` Thierry Reding
2019-04-15 15:05     ` Manikanta Maddireddy
2019-04-23  9:27       ` Manikanta Maddireddy
2019-04-11 17:03 ` [PATCH 14/30] PCI: tegra: Set target speed as Gen1 before link up Manikanta Maddireddy
2019-04-11 20:04   ` Bjorn Helgaas
2019-04-12  6:44     ` Manikanta Maddireddy
2019-04-12 14:35       ` Bjorn Helgaas
2019-04-15 10:43         ` Manikanta Maddireddy
2019-04-15 11:52   ` Thierry Reding
2019-04-15 15:12     ` Manikanta Maddireddy
2019-04-11 17:03 ` [PATCH 15/30] PCI: tegra: Fix PLLE powerdown issue due to CLKREQ# signal Manikanta Maddireddy
2019-04-15 13:17   ` Thierry Reding
2019-04-15 15:14     ` Manikanta Maddireddy
2019-04-11 17:03 ` [PATCH 16/30] PCI: tegra: Program AFI_CACHE* registers only for Tegra20 Manikanta Maddireddy
2019-04-15 13:20   ` Thierry Reding
2019-04-16 10:47     ` Manikanta Maddireddy
2019-04-16 16:11       ` Thierry Reding
2019-04-11 17:03 ` [PATCH 17/30] PCI: tegra: Use switch statements in tegra_pcie_isr() Manikanta Maddireddy
2019-04-15 13:25   ` Thierry Reding
2019-04-15 15:25     ` Manikanta Maddireddy
2019-04-11 17:03 ` [PATCH 18/30] PCI: tegra: Change PRSNT_SENSE irq log to debug Manikanta Maddireddy
2019-04-11 17:03 ` [PATCH 19/30] PCI: tegra: Use legacy irq for port service drivers Manikanta Maddireddy
2019-04-15 13:35   ` Thierry Reding
2019-04-11 17:03 ` [PATCH 20/30] PCI: tegra: Add AFI_PEX2_CTRL reg offset as part of soc struct Manikanta Maddireddy
2019-04-15 13:31   ` Thierry Reding
2019-04-11 17:03 ` [PATCH 21/30] PCI: tegra: Add "pci" type check before parsing child device tree node Manikanta Maddireddy
2019-04-15 13:37   ` Thierry Reding
2019-04-15 15:30     ` Manikanta Maddireddy
2019-04-15 15:42       ` Thierry Reding
2019-04-11 17:03 ` [PATCH 22/30] PCI: tegra: Access endpoint config only if PCIe link is up Manikanta Maddireddy
2019-04-11 20:15   ` Bjorn Helgaas [this message]
2019-04-12  7:00     ` Manikanta Maddireddy
2019-04-12 14:50       ` Bjorn Helgaas
2019-04-15 11:36         ` Manikanta Maddireddy
2019-04-15 13:45           ` Thierry Reding
2019-04-15 13:52             ` Thierry Reding
2019-04-15 14:04           ` Bjorn Helgaas
2019-04-15 15:43             ` Manikanta Maddireddy
2019-04-23 20:24               ` Bjorn Helgaas
2019-04-11 17:03 ` [PATCH 23/30] dt-bindings: pci: tegra: Document PCIe DPD pinctrl optional prop Manikanta Maddireddy
2019-04-15 14:07   ` Thierry Reding
2019-04-15 15:48     ` Manikanta Maddireddy
2019-04-11 17:03 ` [PATCH 24/30] arm64: tegra: Add PEX DPD states as pinctrl properties Manikanta Maddireddy
2019-04-11 17:03 ` [PATCH 25/30] PCI: tegra: Put PEX CLK & BIAS pads in DPD mode Manikanta Maddireddy
2019-04-15 14:11   ` Thierry Reding
2019-04-11 17:03 ` [PATCH 26/30] dt-bindings: pci: tegra: Document nvidia,plat-gpios optional prop Manikanta Maddireddy
2019-04-11 20:18   ` Bjorn Helgaas
2019-04-12  7:01     ` Manikanta Maddireddy
2019-04-15 14:16   ` Thierry Reding
2019-04-15 17:58     ` Manikanta Maddireddy
2019-04-16 15:34       ` Thierry Reding
2019-04-17 11:22         ` Manikanta Maddireddy
2019-04-17 15:19           ` Thierry Reding
2019-04-17 18:26             ` Manikanta Maddireddy
2019-04-11 17:03 ` [PATCH 27/30] PCI: tegra: Add support to configure platform GPIOs Manikanta Maddireddy
2019-04-11 17:03 ` [PATCH 28/30] dt-bindings: pci: tegra: Document nvidia,rst-gpio optional prop Manikanta Maddireddy
2019-04-15 14:20   ` Thierry Reding
2019-04-15 18:01     ` Manikanta Maddireddy
2019-04-29 18:33     ` Rob Herring
2019-04-11 17:03 ` [PATCH 29/30] PCI: tegra: Add support for GPIO based PCIe reset Manikanta Maddireddy
2019-04-15 14:20   ` Thierry Reding
2019-04-15 18:03     ` Manikanta Maddireddy
2019-04-11 17:03 ` [PATCH 30/30] PCI: tegra: Change link retry log level to INFO Manikanta Maddireddy
2019-04-15 14:23   ` Thierry Reding
2019-04-15 18:05     ` Manikanta Maddireddy

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