Re: [PATCH net-next 3/7] qed: Add support for RoCE hw init

Bjorn Helgaas
2022-10-07T15:48:36Z

[+cc Manish, linux-pci]

On Sat, Oct 01, 2016 at 09:59:57PM +0300, Yuval Mintz wrote:
> From: Ram Amrani <Ram.Amrani@caviumnetworks.com>
>
> This adds the backbone required for the various HW initalizations
> which are necessary for the qedr driver - FW notification, resource
> initializations, etc.
> ...

> diff --git a/drivers/net/ethernet/qlogic/qed/qed_roce.c b/drivers/net/ethernet/qlogic/qed/qed_roce.c
> ...
> + /* Check atomic operations support in PCI configuration space. */
> + pci_read_config_dword(cdev->pdev,
> + cdev->pdev->pcie_cap + PCI_EXP_DEVCTL2,
> + &pci_status_control);
> +
> + if (pci_status_control & PCI_EXP_DEVCTL2_LTR_EN)
> + SET_FIELD(dev->dev_caps, QED_RDMA_DEV_CAP_ATOMIC_OP, 1);

I don't understand this.

1) PCI_EXP_DEVCTL2 is a 16-bit register ("word"), not a 32-bit one
("dword").

2) QED_RDMA_DEV_CAP_ATOMIC_OP is set here but is not read anywhere
in this patch. Is it used by the qed device itself?

3) PCI_EXP_DEVCTL2_LTR_EN is for Latency Tolerance Reporting and is
not related to atomic ops. I don't know what
QED_RDMA_DEV_CAP_ATOMIC_OP means, but possibly one of these was
intended instead?

- PCI_EXP_DEVCAP2_ATOMIC_COMP32 means the device supports 32-bit
AtomicOps as a completer.
- PCI_EXP_DEVCAP2_ATOMIC_COMP64 means the device supports 64-bit
AtomicOps as a completer.
- PCI_EXP_DEVCAP2_ATOMIC_COMP128 means the device supports 128-bit
AtomicOps as a completer.
- PCI_EXP_DEVCTL2_ATOMIC_REQ means the device is allowed to
initiate AtomicOps.

(This code is now in qed_rdma.c)