Re: [PATCH RESEND v4 01/15] PCI: dwc: Add more verbose link-up message

Manivannan Sadhasivam
2022-08-01T13:00:11Z

On Fri, Jun 24, 2022 at 05:39:33PM +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@baikalelectronics.ru>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

Thanks,
Mani

> Reviewed-by: Rob Herring <robh@kernel.org>
>
> ---
>
> Changelog v2:
> - Test the error condition first and return straight away if it comes true.
> The typical return is better to be unindented (@Joe).
> ---
> drivers/pci/controller/dwc/pcie-designware.c | 22 ++++++++++++++------
> 1 file changed, 16 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index ce01187947c9..e66d16a86168 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -524,20 +524,30 @@ void dw_pcie_disable_atu(struct dw_pcie *pci, int index,
>
> int dw_pcie_wait_for_link(struct dw_pcie *pci)
> {
> + u32 offset, val;
> int retries;
>
> /* 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) {
> + dev_err(pci->dev, "Phy link never came up\n");
> + return -ETIMEDOUT;
> + }
> +
> + offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> + val = dw_pcie_readw_dbi(pci, offset + PCI_EXP_LNKSTA);
>
> - return -ETIMEDOUT;
> + 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));
> +
> + return 0;
> }
> EXPORT_SYMBOL_GPL(dw_pcie_wait_for_link);
>
> --
> 2.35.1
>

--
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