drivers/pci/controller/dwc/pcie-designware-host.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
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@google.com>
---
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-googOn Mon, Feb 27, 2023, Sajid Dalvi <sdalvi@google.com> 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@google.com> (CC'ed Krzysztof Kozlowski) Acked-by: Jingoo Han <jingoohan1@gmail.com> 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 >
Thanks for your review Jingoo. Sajid On Tue, Feb 28, 2023 at 4:04 PM Han Jingoo <jingoohan1@gmail.com> wrote: > > On Mon, Feb 27, 2023, Sajid Dalvi <sdalvi@google.com> 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@google.com> > > (CC'ed Krzysztof Kozlowski) > > Acked-by: Jingoo Han <jingoohan1@gmail.com> > > 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 > >
On Tue, Feb 28, 2023 at 10:36 PM Sajid Dalvi <sdalvi@google.com> wrote: > > Thanks for your review Jingoo. > Sajid > > On Tue, Feb 28, 2023 at 4:04 PM Han Jingoo <jingoohan1@gmail.com> wrote: > > > > On Mon, Feb 27, 2023, Sajid Dalvi <sdalvi@google.com> 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@google.com> > > > > (CC'ed Krzysztof Kozlowski) > > > > Acked-by: Jingoo Han <jingoohan1@gmail.com> > > > > 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/ Thanks Sajid
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@google.com> wrote: > > > > Thanks for your review Jingoo. > > Sajid > > > > On Tue, Feb 28, 2023 at 4:04 PM Han Jingoo <jingoohan1@gmail.com> wrote: > > > > > > On Mon, Feb 27, 2023, Sajid Dalvi <sdalvi@google.com> 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@google.com> > > > > > > (CC'ed Krzysztof Kozlowski) > > > > > > Acked-by: Jingoo Han <jingoohan1@gmail.com> > > > > > > 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. I guess the only way to know is merging this path and check the fallout. Lorenzo
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@google.com> wrote:
> > >
> > > Thanks for your review Jingoo.
> > > Sajid
> > >
> > > On Tue, Feb 28, 2023 at 4:04 PM Han Jingoo <jingoohan1@gmail.com> wrote:
> > > >
> > > > On Mon, Feb 27, 2023, Sajid Dalvi <sdalvi@google.com> 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@google.com>
> > > >
> > > > (CC'ed Krzysztof Kozlowski)
> > > >
> > > > Acked-by: Jingoo Han <jingoohan1@gmail.com>
> > > >
> > > > 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
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@google.com> wrote:
> > > >
> > > > Thanks for your review Jingoo.
> > > > Sajid
> > > >
> > > > On Tue, Feb 28, 2023 at 4:04 PM Han Jingoo <jingoohan1@gmail.com> wrote:
> > > > >
> > > > > On Mon, Feb 27, 2023, Sajid Dalvi <sdalvi@google.com> 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@google.com>
> > > > >
> > > > > (CC'ed Krzysztof Kozlowski)
> > > > >
> > > > > Acked-by: Jingoo Han <jingoohan1@gmail.com>
> > > > >
> > > > > 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@android.com.
>
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@baikalelectronics.ru/
Regards,
Will
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@google.com> wrote:
> > > > >
> > > > > Thanks for your review Jingoo.
> > > > > Sajid
> > > > >
> > > > > On Tue, Feb 28, 2023 at 4:04 PM Han Jingoo <jingoohan1@gmail.com> wrote:
> > > > > >
> > > > > > On Mon, Feb 27, 2023, Sajid Dalvi <sdalvi@google.com> 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@google.com>
> > > > > >
> > > > > > (CC'ed Krzysztof Kozlowski)
> > > > > >
> > > > > > Acked-by: Jingoo Han <jingoohan1@gmail.com>
> > > > > >
> > > > > > 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@android.com.
> >
>
> 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@baikalelectronics.ru/
>
> 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;
+ /* 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) {
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@google.com> wrote:
> > > > > >
> > > > > > Thanks for your review Jingoo.
> > > > > > Sajid
> > > > > >
> > > > > > On Tue, Feb 28, 2023 at 4:04 PM Han Jingoo <jingoohan1@gmail.com> wrote:
> > > > > > >
> > > > > > > On Mon, Feb 27, 2023, Sajid Dalvi <sdalvi@google.com> 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@google.com>
> > > > > > >
> > > > > > > (CC'ed Krzysztof Kozlowski)
> > > > > > >
> > > > > > > Acked-by: Jingoo Han <jingoohan1@gmail.com>
> > > > > > >
> > > > > > > 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@android.com.
> > >
> >
> > 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@baikalelectronics.ru/
> >
> > 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.
Here is my attempt at a patch which can satisfy all the requirements
(Ideally, I did not want to use `pci->ops` in the host driver but I
could not figure out any other way):
diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c
b/drivers/pci/controller/dwc/pcie-designware-host.c
index 9952057c8819..39c7219ec7c9 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -485,15 +485,18 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
if (ret)
goto err_remove_edma;
- if (!dw_pcie_link_up(pci)) {
- ret = dw_pcie_start_link(pci);
+ ret = dw_pcie_start_link(pci);
+ if (ret)
+ goto err_remove_edma;
+
+ if (dw_pcie_link_up(pci)) {
+ dw_pcie_print_link_status(pci);
+ } else if (pci->ops && pci->ops->start_link) {
+ ret = dw_pcie_wait_for_link(pci);
if (ret)
- goto err_remove_edma;
+ goto err_stop_link;
}
- /* Ignore errors, the link may come up later */
- dw_pcie_wait_for_link(pci);
-
bridge->sysdata = pp;
ret = pci_host_probe(bridge);
diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index 53a16b8b6ac2..03748a8dffd3 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -644,9 +644,20 @@ 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 */
@@ -662,12 +673,7 @@ 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;
}
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index 79713ce075cc..615660640801 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -429,6 +429,7 @@ 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);
static inline void dw_pcie_writel_dbi(struct dw_pcie *pci, u32 reg, u32 val)
{
On 04/06/2023, 'Ajay Agarwal' via kernel-team wrote:
> Here is my attempt at a patch which can satisfy all the requirements
> (Ideally, I did not want to use `pci->ops` in the host driver but I
> could not figure out any other way):
>
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c
> b/drivers/pci/controller/dwc/pcie-designware-host.c
> index 9952057c8819..39c7219ec7c9 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -485,15 +485,18 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
> if (ret)
> goto err_remove_edma;
>
> - if (!dw_pcie_link_up(pci)) {
> - ret = dw_pcie_start_link(pci);
> + ret = dw_pcie_start_link(pci);
> + if (ret)
> + goto err_remove_edma;
> +
> + if (dw_pcie_link_up(pci)) {
> + dw_pcie_print_link_status(pci);
> + } else if (pci->ops && pci->ops->start_link) {
> + ret = dw_pcie_wait_for_link(pci);
> if (ret)
> - goto err_remove_edma;
> + goto err_stop_link;
> }
>
> - /* Ignore errors, the link may come up later */
> - dw_pcie_wait_for_link(pci);
> -
> bridge->sysdata = pp;
>
> ret = pci_host_probe(bridge);
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index 53a16b8b6ac2..03748a8dffd3 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -644,9 +644,20 @@ 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 */
> @@ -662,12 +673,7 @@ 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;
> }
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 79713ce075cc..615660640801 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -429,6 +429,7 @@ 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);
>
> static inline void dw_pcie_writel_dbi(struct dw_pcie *pci, u32 reg, u32 val)
> {
>
> --
> To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com.
>
Thanks Ajay for the follow-up patch! I've tested it out on a Pixel 6 and
it's working as intended for me. Probing the PCIe RC device now only
take 0.02s vs ~1.02s. If others don't object, please send it as a v3
patch.
Thanks,
Will
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