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 [thread overview]
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
>
next prev parent reply other threads:[~2019-04-11 20:15 UTC|newest]
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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