[+cc Bjorn A, Fabio, Xiaolei, who reported the v4 issue]
On Fri, Jan 12, 2024 at 03:00:06PM +0530, Ajay Agarwal wrote:
> In dw_pcie_host_init() regardless of whether the link has been
> started or not, the code waits for the link to come up. Even in
> cases where start_link() is not defined the code ends up spinning
> in a loop for 1 second. Since in some systems dw_pcie_host_init()
> gets called during probe, this one second loop for each pcie
> interface instance ends up extending the boot time.
s/start_link()/.start_link()/ to hint that this is a function pointer,
not a function name in its own right (also below).
s/1/one/ to be consistent.
s/pcie/PCIe/ to follow spec usage.
> Wait for the link up in only if the start_link() is defined.
>
> Signed-off-by: Ajay Agarwal <ajayagarwal@xxxxxxxxxx>
> ---
> v4 was applied, but then reverted. The reason being v4 added a
> regression on some products which expect the link to not come up as a
> part of the probe. Since v4 returned error from dw_pcie_wait_for_link
> check, the probe function of these products started to fail.
I know this part doesn't get included in the commit log, but I think
it would be nice to include the relevant commits here:
da56a1bfbab5 ("PCI: dwc: Wait for link up only if link is started")
c5097b9869a1 ("Revert "PCI: dwc: Wait for link up only if link is started"")
because the latter includes details about the actual failure, so we
can review this with that platform in mind.
> Changelog since v4:
> - Do not return error from dw_pcie_wait_for_link check
>
> .../pci/controller/dwc/pcie-designware-host.c | 12 +++++++----
> drivers/pci/controller/dwc/pcie-designware.c | 20 ++++++++++++-------
> drivers/pci/controller/dwc/pcie-designware.h | 1 +
> 3 files changed, 22 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index 7991f0e179b2..e53132663d1d 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -487,14 +487,18 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
> if (ret)
> goto err_remove_edma;
>
> - if (!dw_pcie_link_up(pci)) {
> + if (dw_pcie_link_up(pci)) {
> + dw_pcie_print_link_status(pci);
> + } else {
> ret = dw_pcie_start_link(pci);
> if (ret)
> goto err_remove_edma;
> - }
>
> - /* Ignore errors, the link may come up later */
> - dw_pcie_wait_for_link(pci);
> + if (pci->ops && pci->ops->start_link) {
> + /* Ignore errors, the link may come up later */
> + dw_pcie_wait_for_link(pci);
> + }
> + }
>
> bridge->sysdata = pp;
>
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index 250cf7f40b85..c067d2e960cf 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -645,9 +645,20 @@ void dw_pcie_disable_atu(struct dw_pcie *pci, u32 dir, int index)
> dw_pcie_writel_atu(pci, dir, index, PCIE_ATU_REGION_CTRL2, 0);
> }
>
> -int dw_pcie_wait_for_link(struct dw_pcie *pci)
> +void dw_pcie_print_link_status(struct dw_pcie *pci)
> {
> 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));
> +}
> +
> +int dw_pcie_wait_for_link(struct dw_pcie *pci)
> +{
> int retries;
>
> /* Check if the link is up or not */
> @@ -663,12 +674,7 @@ int dw_pcie_wait_for_link(struct dw_pcie *pci)
> return -ETIMEDOUT;
> }
>
> - 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));
> + dw_pcie_print_link_status(pci);
>
> return 0;
> }
This part (pcie-designware.c and pcie-designware.h changes) could
arguably be in a separate patch so they're not a distraction from the
important functional change.
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 55ff76e3d384..164214a7219a 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -447,6 +447,7 @@ void dw_pcie_setup(struct dw_pcie *pci);
> void dw_pcie_iatu_detect(struct dw_pcie *pci);
> int dw_pcie_edma_detect(struct dw_pcie *pci);
> void dw_pcie_edma_remove(struct dw_pcie *pci);
> +void dw_pcie_print_link_status(struct dw_pcie *pci);
>
> int dw_pcie_suspend_noirq(struct dw_pcie *pci);
> int dw_pcie_resume_noirq(struct dw_pcie *pci);
> --
> 2.43.0.381.gb435a96ce8-goog
>
