On Mon, Mar 28, 2022 at 04:31:53PM -0700, Joe Perches wrote:
> On Thu, 2022-03-24 at 04:37 +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
> []
> > @@ -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));
> > +
> > + return 0;
> > + }
> > +
> > + dev_err(pci->dev, "Phy link never came up\n");
> >
> > return -ETIMEDOUT;
> > }
>
> IMO: it's generally bette to test the error condition and unindent
> the typical return.
Absolutely right. Thanks for noticing that. No idea why I haven't done
the way you said 'cause it seems neater, more maintainable than what I
suggested here.
-Sergey
>
> if (retries >= LINK_WAIT_MAX_RETRIES) {
> dev_err(pci->dev, "Phy link never came up\n");
> return -ETIMEDOUT;
> }
>
> offset = ...
> val = ...
> dev_info(...)
>
> return 0;
> }
>
