On Wed, Apr 05, 2023 at 12:23:47PM -0700, William McVicker wrote: > On 04/05/2023, William McVicker wrote: > > On 04/05/2023, Bjorn Helgaas wrote: > > > On Wed, Apr 05, 2023 at 03:24:36PM +0200, Lorenzo Pieralisi wrote: > > > > On Thu, Mar 16, 2023 at 06:05:02PM -0500, Sajid Dalvi wrote: > > > > > On Tue, Feb 28, 2023 at 10:36 PM Sajid Dalvi <sdalvi@xxxxxxxxxx> wrote: > > > > > > > > > > > > Thanks for your review Jingoo. > > > > > > Sajid > > > > > > > > > > > > On Tue, Feb 28, 2023 at 4:04 PM Han Jingoo <jingoohan1@xxxxxxxxx> wrote: > > > > > > > > > > > > > > On Mon, Feb 27, 2023, Sajid Dalvi <sdalvi@xxxxxxxxxx> 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. > > > > > > > > > > > > > > > > Call trace when start_link() is not defined: > > > > > > > > dw_pcie_wait_for_link << spins in a loop for 1 second > > > > > > > > dw_pcie_host_init > > > > > > > > > > > > > > > > Signed-off-by: Sajid Dalvi <sdalvi@xxxxxxxxxx> > > > > > > > > > > > > > > (CC'ed Krzysztof Kozlowski) > > > > > > > > > > > > > > Acked-by: Jingoo Han <jingoohan1@xxxxxxxxx> > > > > > > > > > > > > > > It looks good to me. I also checked the previous thread. > > > > > > > I agree with Krzysztof's opinion that we should include > > > > > > > only hardware-related features into DT. > > > > > > > Thank you. > > > > > > > > > > > > > > Best regards, > > > > > > > Jingoo Han > > > > > > > > > > > > > > > --- > > > > > > > > drivers/pci/controller/dwc/pcie-designware-host.c | 6 +++--- > > > > > > > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > > > > > > > > > > > > > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c > > > > > > > > index 9952057c8819..9709f69f173e 100644 > > > > > > > > --- a/drivers/pci/controller/dwc/pcie-designware-host.c > > > > > > > > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c > > > > > > > > @@ -489,10 +489,10 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp) > > > > > > > > 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); > > > > > > > > + /* Ignore errors, the link may come up later */ > > > > > > > > + dw_pcie_wait_for_link(pci); > > > > > > > > + } > > > > > > > > > > > > > > > > bridge->sysdata = pp; > > > > > > > > > > > > > > > > -- > > > > > > > > 2.39.2.722.g9855ee24e9-goog > > > > > > > > > > > > > > > > > > @bhelgaas Can this be picked up in your tree: > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/ > > > > > > > > This patch seems fine to me. The question I have though is why the > > > > *current* code is written the way it is. Perhaps it is just the way > > > > it is, I wonder whether this change can trigger a regression though. > > > > > > The new code will look basically like this: > > > > > > if (!dw_pcie_link_up(pci)) { > > > dw_pcie_start_link(pci); > > > dw_pcie_wait_for_link(pci); > > > } > > > > > > If the link is already up by the time we get here, this change means > > > we won't get this message emitted by dw_pcie_wait_for_link(): > > > > > > dev_info(pci->dev, "PCIe Gen.%u x%u link up\n", ...) > > > > > > I don't know how important that is, but I bet somebody cares about it. > > > > > > From the commit log, I expected the patch to do something based on > > > whether ->start_link() was defined, but there really isn't a direct > > > connection, so maybe the log could be refined. > > > > > > Bjorn > > > > > > -- > > > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@xxxxxxxxxxx. > > > > > > > After taking a deeper dive into this patch, I found that [1] changes the > > original intent which was to skip the call to dw_pcie_wait_for_link() > > when pci->ops->start_link is NULL. I talked to Sajid offline and he > > agreed we should put back the start_link NULL check. The updated patch > > should look like this: > > > > if (!dw_pcie_link_up(pci) && pci->ops && pci->ops->start_link) { > > ret = dw_pcie_start_link(pci); > > if (ret) > > goto err_free_msi; > > dw_pcie_wait_for_link(pci); > > } > > > > > > ...which will ensure that we don't call dw_pcie_wait_for_link() when > > pci->ops->start_link is NULL. > > > > With regards to the log, I think there are 2 ways to solve this: > > > > 1) We could also call dw_pcie_wait_for_link() in a new else if > > dw_pcie_link_up() returns 1. > > 2) We could add this to the top of dw_pcie_wait_for_link() and leave the > > code as is: > > > > if (!pci->ops || !pci->ops->start_link) > > return 0; > > > > I kind of like (2) since that solves both Sajid's original issue and > > will keep the original log. > > > > [1] https://lore.kernel.org/all/20220624143428.8334-14-Sergey.Semin@xxxxxxxxxxxxxxxxxxxx/ > > > > Regards, > > Will > > Below is what I'm thinking will do the job. I verified on a Pixel 6 > (which doesn't have start_link() defined) that we don't have the 1 > second wait from dw_pcie_wait_for_link() during probe. > > diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c > index 8e33e6e59e68..1bf04324ad2d 100644 > --- a/drivers/pci/controller/dwc/pcie-designware.c > +++ b/drivers/pci/controller/dwc/pcie-designware.c > @@ -648,13 +648,16 @@ int dw_pcie_wait_for_link(struct dw_pcie *pci) > { > u32 offset, val; > int retries; > + int link_up = dw_pcie_link_up(pci); > > - /* Check if the link is up or not */ > - for (retries = 0; retries < LINK_WAIT_MAX_RETRIES; retries++) { > - if (dw_pcie_link_up(pci)) > - break; > + if (!link_up && !(pci->ops && pci->ops->start_link)) > + return 0; There is a problem with this approach. A platform driver could enable link training internally, i.e., it does not have the start_link() pointer defined. Then it could call `dw_pcie_wait_for_link` to wait for the link to come up. (See pcie-intel-gw.c for an example of such a platform). Your logic will end up regressing this driver by exiting early. > > + /* Check if the link is up or not */ > + for (retries = 0; !link_up && retries < LINK_WAIT_MAX_RETRIES; retries++) { > usleep_range(LINK_WAIT_USLEEP_MIN, LINK_WAIT_USLEEP_MAX); > + > + link_up = dw_pcie_link_up(pci); > } > > if (retries >= LINK_WAIT_MAX_RETRIES) { > The problem of the log is still not solved for a platform which could have the link up by default, i.e., it does not need to explicitly enable link training.
