On Thu, Mar 24, 2022 at 04:37:21AM +0300, Serge Semin wrote:
> Printing just "link up" isn't that much informative especially when it
> comes to working with the PCI Express bus. Even if the link is up, due to
> multiple reasons the bus performance can degrade to slower speeds or to
> narrower width than both Root Port and its partner is capable of. In that
> case it would be handy to know the link specifications as early as
> possible. So let's add a more verbose message to the busy-wait link-state
> method, which will contain the link speed generation and the PCIe bus
> width in case if the link up state is discovered. Otherwise an error will
> be printed to the system log.
>
> Signed-off-by: Serge Semin <Sergey.Semin@xxxxxxxxxxxxxxxxxxxx>
> ---
> drivers/pci/controller/dwc/pcie-designware.c | 22 +++++++++++++++-----
> 1 file changed, 17 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index 6e81264fdfb4..f1693e25afcb 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -528,14 +528,26 @@ int dw_pcie_wait_for_link(struct dw_pcie *pci)
>
> /* Check if the link is up or not */
> for (retries = 0; retries < LINK_WAIT_MAX_RETRIES; retries++) {
> - if (dw_pcie_link_up(pci)) {
> - dev_info(pci->dev, "Link up\n");
> - return 0;
> - }
> + if (dw_pcie_link_up(pci))
> + break;
> +
> usleep_range(LINK_WAIT_USLEEP_MIN, LINK_WAIT_USLEEP_MAX);
> }
>
> - dev_info(pci->dev, "Phy link never came up\n");
> + if (retries < LINK_WAIT_MAX_RETRIES) {
> + u32 offset, val;
> +
> + offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> + val = dw_pcie_readw_dbi(pci, offset + PCI_EXP_LNKSTA);
> +
> + dev_info(pci->dev, "PCIe Gen.%u x%u link up\n",
> + FIELD_GET(PCI_EXP_LNKSTA_CLS, val),
> + FIELD_GET(PCI_EXP_LNKSTA_NLW, val));
Given these are standard registers can we do this in the core code? The
main issue I think is that the config space accessors don't work until
you create the bus struct. That still should be early enough.
I think it is possible some implementations don't report the link state
in these registers. Maybe we don't really need to care.
Rob
