* [PATCH] ARM: imx6: Fix "BUG: scheduling while atomic" if PCIe switch is attached
@ 2015-06-18 7:56 ` David Müller
0 siblings, 0 replies; 14+ messages in thread
From: David Müller @ 2015-06-18 7:56 UTC (permalink / raw)
To: linux-arm-kernel
This problem has already been reported as
https://bugzilla.kernel.org/show_bug.cgi?id=100031
Signed-off-by: David M?ller <dave.mueller@gmx.ch>
---
drivers/pci/host/pci-imx6.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
index fdb9536..c63691c 100644
--- a/drivers/pci/host/pci-imx6.c
+++ b/drivers/pci/host/pci-imx6.c
@@ -489,7 +489,7 @@ static int imx6_pcie_link_up(struct pcie_port *pp)
* Wait a little bit, then re-check if the link finished
* the training.
*/
- usleep_range(1000, 2000);
+ mdelay(20);
}
/*
* From L0, initiate MAC entry to gen2 if EP/RC supports gen2.
--
1.8.4
^ permalink raw reply related [flat|nested] 14+ messages in thread
* Re: [PATCH] ARM: imx6: Fix "BUG: scheduling while atomic" if PCIe switch is attached
2015-06-18 7:56 ` David Müller
@ 2015-06-18 8:27 ` Lucas Stach
-1 siblings, 0 replies; 14+ messages in thread
From: Lucas Stach @ 2015-06-18 8:27 UTC (permalink / raw)
To: David Müller; +Cc: linux-pci, Richard Zhu, Bjorn Helgaas, linux-arm-kernel
Am Donnerstag, den 18.06.2015, 09:56 +0200 schrieb David Müller:
> This problem has already been reported as
> https://bugzilla.kernel.org/show_bug.cgi?id=100031
>
> Signed-off-by: David Müller <dave.mueller@gmx.ch>
> ---
> drivers/pci/host/pci-imx6.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
> index fdb9536..c63691c 100644
> --- a/drivers/pci/host/pci-imx6.c
> +++ b/drivers/pci/host/pci-imx6.c
> @@ -489,7 +489,7 @@ static int imx6_pcie_link_up(struct pcie_port *pp)
> * Wait a little bit, then re-check if the link finished
> * the training.
> */
> - usleep_range(1000, 2000);
> + mdelay(20);
While switching to mdelay might be the right thing to do here, you are
also changing the timeout. This is a change in behavior and so not okay.
Especially as you keep the CPU spinning for the duration of that
timeout.
> }
> /*
> * From L0, initiate MAC entry to gen2 if EP/RC supports gen2.
--
Pengutronix e.K. | Lucas Stach |
Industrial Linux Solutions | http://www.pengutronix.de/ |
^ permalink raw reply [flat|nested] 14+ messages in thread
* [PATCH] ARM: imx6: Fix "BUG: scheduling while atomic" if PCIe switch is attached
@ 2015-06-18 8:27 ` Lucas Stach
0 siblings, 0 replies; 14+ messages in thread
From: Lucas Stach @ 2015-06-18 8:27 UTC (permalink / raw)
To: linux-arm-kernel
Am Donnerstag, den 18.06.2015, 09:56 +0200 schrieb David M?ller:
> This problem has already been reported as
> https://bugzilla.kernel.org/show_bug.cgi?id=100031
>
> Signed-off-by: David M?ller <dave.mueller@gmx.ch>
> ---
> drivers/pci/host/pci-imx6.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
> index fdb9536..c63691c 100644
> --- a/drivers/pci/host/pci-imx6.c
> +++ b/drivers/pci/host/pci-imx6.c
> @@ -489,7 +489,7 @@ static int imx6_pcie_link_up(struct pcie_port *pp)
> * Wait a little bit, then re-check if the link finished
> * the training.
> */
> - usleep_range(1000, 2000);
> + mdelay(20);
While switching to mdelay might be the right thing to do here, you are
also changing the timeout. This is a change in behavior and so not okay.
Especially as you keep the CPU spinning for the duration of that
timeout.
> }
> /*
> * From L0, initiate MAC entry to gen2 if EP/RC supports gen2.
--
Pengutronix e.K. | Lucas Stach |
Industrial Linux Solutions | http://www.pengutronix.de/ |
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH] ARM: imx6: Fix "BUG: scheduling while atomic" if PCIe switch is attached
2015-06-18 8:27 ` Lucas Stach
@ 2015-06-22 13:30 ` Fabio Estevam
-1 siblings, 0 replies; 14+ messages in thread
From: Fabio Estevam @ 2015-06-22 13:30 UTC (permalink / raw)
To: Lucas Stach
Cc: David Müller, linux-pci, Richard Zhu, Bjorn Helgaas,
linux-arm-kernel
On Thu, Jun 18, 2015 at 5:27 AM, Lucas Stach <l.stach@pengutronix.de> wrote:
>> diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
>> index fdb9536..c63691c 100644
>> --- a/drivers/pci/host/pci-imx6.c
>> +++ b/drivers/pci/host/pci-imx6.c
>> @@ -489,7 +489,7 @@ static int imx6_pcie_link_up(struct pcie_port *pp)
>> * Wait a little bit, then re-check if the link finished
>> * the training.
>> */
>> - usleep_range(1000, 2000);
>> + mdelay(20);
>
> While switching to mdelay might be the right thing to do here, you are
> also changing the timeout. This is a change in behavior and so not okay.
msleep(2) is not recommended according to Documentation/timers/timers-howto.txt.
What would be the proper fix then?
Regards,
Fabio Estevam
--
To unsubscribe from this list: send the line "unsubscribe linux-pci" in
^ permalink raw reply [flat|nested] 14+ messages in thread
* [PATCH] ARM: imx6: Fix "BUG: scheduling while atomic" if PCIe switch is attached
@ 2015-06-22 13:30 ` Fabio Estevam
0 siblings, 0 replies; 14+ messages in thread
From: Fabio Estevam @ 2015-06-22 13:30 UTC (permalink / raw)
To: linux-arm-kernel
On Thu, Jun 18, 2015 at 5:27 AM, Lucas Stach <l.stach@pengutronix.de> wrote:
>> diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
>> index fdb9536..c63691c 100644
>> --- a/drivers/pci/host/pci-imx6.c
>> +++ b/drivers/pci/host/pci-imx6.c
>> @@ -489,7 +489,7 @@ static int imx6_pcie_link_up(struct pcie_port *pp)
>> * Wait a little bit, then re-check if the link finished
>> * the training.
>> */
>> - usleep_range(1000, 2000);
>> + mdelay(20);
>
> While switching to mdelay might be the right thing to do here, you are
> also changing the timeout. This is a change in behavior and so not okay.
msleep(2) is not recommended according to Documentation/timers/timers-howto.txt.
What would be the proper fix then?
Regards,
Fabio Estevam
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH] ARM: imx6: Fix "BUG: scheduling while atomic" if PCIe switch is attached
2015-06-22 13:30 ` Fabio Estevam
@ 2015-06-22 13:37 ` Lucas Stach
-1 siblings, 0 replies; 14+ messages in thread
From: Lucas Stach @ 2015-06-22 13:37 UTC (permalink / raw)
To: Fabio Estevam
Cc: David Müller, linux-pci, Richard Zhu, Bjorn Helgaas,
linux-arm-kernel
Am Montag, den 22.06.2015, 10:30 -0300 schrieb Fabio Estevam:
> On Thu, Jun 18, 2015 at 5:27 AM, Lucas Stach <l.stach@pengutronix.de> wrote:
>
> >> diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
> >> index fdb9536..c63691c 100644
> >> --- a/drivers/pci/host/pci-imx6.c
> >> +++ b/drivers/pci/host/pci-imx6.c
> >> @@ -489,7 +489,7 @@ static int imx6_pcie_link_up(struct pcie_port *pp)
> >> * Wait a little bit, then re-check if the link finished
> >> * the training.
> >> */
> >> - usleep_range(1000, 2000);
> >> + mdelay(20);
> >
> > While switching to mdelay might be the right thing to do here, you are
> > also changing the timeout. This is a change in behavior and so not okay.
>
> msleep(2) is not recommended according to Documentation/timers/timers-howto.txt.
>
> What would be the proper fix then?
>
mdelay(2) is completely reasonable. Note the difference between delay
and sleep.
The mid-term correct solution would be to move all the link-up handling
out of the atomic path.
Regards,
Lucas
--
Pengutronix e.K. | Lucas Stach |
Industrial Linux Solutions | http://www.pengutronix.de/ |
--
To unsubscribe from this list: send the line "unsubscribe linux-pci" in
^ permalink raw reply [flat|nested] 14+ messages in thread
* [PATCH] ARM: imx6: Fix "BUG: scheduling while atomic" if PCIe switch is attached
@ 2015-06-22 13:37 ` Lucas Stach
0 siblings, 0 replies; 14+ messages in thread
From: Lucas Stach @ 2015-06-22 13:37 UTC (permalink / raw)
To: linux-arm-kernel
Am Montag, den 22.06.2015, 10:30 -0300 schrieb Fabio Estevam:
> On Thu, Jun 18, 2015 at 5:27 AM, Lucas Stach <l.stach@pengutronix.de> wrote:
>
> >> diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
> >> index fdb9536..c63691c 100644
> >> --- a/drivers/pci/host/pci-imx6.c
> >> +++ b/drivers/pci/host/pci-imx6.c
> >> @@ -489,7 +489,7 @@ static int imx6_pcie_link_up(struct pcie_port *pp)
> >> * Wait a little bit, then re-check if the link finished
> >> * the training.
> >> */
> >> - usleep_range(1000, 2000);
> >> + mdelay(20);
> >
> > While switching to mdelay might be the right thing to do here, you are
> > also changing the timeout. This is a change in behavior and so not okay.
>
> msleep(2) is not recommended according to Documentation/timers/timers-howto.txt.
>
> What would be the proper fix then?
>
mdelay(2) is completely reasonable. Note the difference between delay
and sleep.
The mid-term correct solution would be to move all the link-up handling
out of the atomic path.
Regards,
Lucas
--
Pengutronix e.K. | Lucas Stach |
Industrial Linux Solutions | http://www.pengutronix.de/ |
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH] ARM: imx6: Fix "BUG: scheduling while atomic" if PCIe switch is attached
2015-06-22 13:37 ` Lucas Stach
@ 2015-06-22 13:46 ` Fabio Estevam
-1 siblings, 0 replies; 14+ messages in thread
From: Fabio Estevam @ 2015-06-22 13:46 UTC (permalink / raw)
To: Lucas Stach
Cc: David Müller, linux-pci, Richard Zhu, Bjorn Helgaas,
linux-arm-kernel
On Mon, Jun 22, 2015 at 10:37 AM, Lucas Stach <l.stach@pengutronix.de> wrote:
> mdelay(2) is completely reasonable. Note the difference between delay
> and sleep.
Oh, that's right :-)
Thanks
--
To unsubscribe from this list: send the line "unsubscribe linux-pci" in
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH] ARM: imx6: Fix "BUG: scheduling while atomic" if PCIe switch is attached
2015-06-18 7:56 ` David Müller
@ 2015-06-18 13:21 ` Bjorn Helgaas
-1 siblings, 0 replies; 14+ messages in thread
From: Bjorn Helgaas @ 2015-06-18 13:21 UTC (permalink / raw)
To: David Müller; +Cc: linux-pci, Richard Zhu, Lucas Stach, linux-arm-kernel
On Thu, Jun 18, 2015 at 09:56:54AM +0200, David Müller wrote:
> This problem has already been reported as
> https://bugzilla.kernel.org/show_bug.cgi?id=100031
>
> Signed-off-by: David Müller <dave.mueller@gmx.ch>
> ---
> drivers/pci/host/pci-imx6.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
> index fdb9536..c63691c 100644
> --- a/drivers/pci/host/pci-imx6.c
> +++ b/drivers/pci/host/pci-imx6.c
> @@ -489,7 +489,7 @@ static int imx6_pcie_link_up(struct pcie_port *pp)
> * Wait a little bit, then re-check if the link finished
> * the training.
> */
> - usleep_range(1000, 2000);
> + mdelay(20);
> }
> /*
> * From L0, initiate MAC entry to gen2 if EP/RC supports gen2.
I asked in the bugzilla why imx6_pcie_link_up() looks nothing like the
other pcie_host_ops.link_up() methods.
Lucas responded:
> the i.MX6 link up routine is a bit more complex compared to the other
> designware drivers because of a hardware bug, where some FIFOs could
> get out of sync when changing the link speed. We need to start the
> link at Gen1, wait for it to be stable, then start a directed link
> speed change if the EP is Gen2 and wait for the link to be stable
> again. If the link doesn't come back, we need to start over.
> I don't think any of the other DW PCIe implementations need this
> workaround.
That explanation makes sense, and a comment to that effect should be
in the code. But I also wonder whether this workaround could be moved
to imx6_pcie_start_link() (just renamed to imx6_pcie_establish_link()).
Then imx6_pcie_link_up() could be a simple status check like the
others.
Bjorn
^ permalink raw reply [flat|nested] 14+ messages in thread
* [PATCH] ARM: imx6: Fix "BUG: scheduling while atomic" if PCIe switch is attached
@ 2015-06-18 13:21 ` Bjorn Helgaas
0 siblings, 0 replies; 14+ messages in thread
From: Bjorn Helgaas @ 2015-06-18 13:21 UTC (permalink / raw)
To: linux-arm-kernel
On Thu, Jun 18, 2015 at 09:56:54AM +0200, David M?ller wrote:
> This problem has already been reported as
> https://bugzilla.kernel.org/show_bug.cgi?id=100031
>
> Signed-off-by: David M?ller <dave.mueller@gmx.ch>
> ---
> drivers/pci/host/pci-imx6.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
> index fdb9536..c63691c 100644
> --- a/drivers/pci/host/pci-imx6.c
> +++ b/drivers/pci/host/pci-imx6.c
> @@ -489,7 +489,7 @@ static int imx6_pcie_link_up(struct pcie_port *pp)
> * Wait a little bit, then re-check if the link finished
> * the training.
> */
> - usleep_range(1000, 2000);
> + mdelay(20);
> }
> /*
> * From L0, initiate MAC entry to gen2 if EP/RC supports gen2.
I asked in the bugzilla why imx6_pcie_link_up() looks nothing like the
other pcie_host_ops.link_up() methods.
Lucas responded:
> the i.MX6 link up routine is a bit more complex compared to the other
> designware drivers because of a hardware bug, where some FIFOs could
> get out of sync when changing the link speed. We need to start the
> link at Gen1, wait for it to be stable, then start a directed link
> speed change if the EP is Gen2 and wait for the link to be stable
> again. If the link doesn't come back, we need to start over.
> I don't think any of the other DW PCIe implementations need this
> workaround.
That explanation makes sense, and a comment to that effect should be
in the code. But I also wonder whether this workaround could be moved
to imx6_pcie_start_link() (just renamed to imx6_pcie_establish_link()).
Then imx6_pcie_link_up() could be a simple status check like the
others.
Bjorn
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH] ARM: imx6: Fix "BUG: scheduling while atomic" if PCIe switch is attached
2015-06-18 7:56 ` David Müller
@ 2015-07-14 18:33 ` Bjorn Helgaas
-1 siblings, 0 replies; 14+ messages in thread
From: Bjorn Helgaas @ 2015-07-14 18:33 UTC (permalink / raw)
To: David Müller; +Cc: linux-pci, Richard Zhu, Lucas Stach, linux-arm-kernel
On Thu, Jun 18, 2015 at 09:56:54AM +0200, David Müller wrote:
> This problem has already been reported as
> https://bugzilla.kernel.org/show_bug.cgi?id=100031
>
> Signed-off-by: David Müller <dave.mueller@gmx.ch>
Dropping for now, hoping for an update addressing the review comments.
> ---
> drivers/pci/host/pci-imx6.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
> index fdb9536..c63691c 100644
> --- a/drivers/pci/host/pci-imx6.c
> +++ b/drivers/pci/host/pci-imx6.c
> @@ -489,7 +489,7 @@ static int imx6_pcie_link_up(struct pcie_port *pp)
> * Wait a little bit, then re-check if the link finished
> * the training.
> */
> - usleep_range(1000, 2000);
> + mdelay(20);
> }
> /*
> * From L0, initiate MAC entry to gen2 if EP/RC supports gen2.
> --
> 1.8.4
>
^ permalink raw reply [flat|nested] 14+ messages in thread
* [PATCH] ARM: imx6: Fix "BUG: scheduling while atomic" if PCIe switch is attached
@ 2015-07-14 18:33 ` Bjorn Helgaas
0 siblings, 0 replies; 14+ messages in thread
From: Bjorn Helgaas @ 2015-07-14 18:33 UTC (permalink / raw)
To: linux-arm-kernel
On Thu, Jun 18, 2015 at 09:56:54AM +0200, David M?ller wrote:
> This problem has already been reported as
> https://bugzilla.kernel.org/show_bug.cgi?id=100031
>
> Signed-off-by: David M?ller <dave.mueller@gmx.ch>
Dropping for now, hoping for an update addressing the review comments.
> ---
> drivers/pci/host/pci-imx6.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
> index fdb9536..c63691c 100644
> --- a/drivers/pci/host/pci-imx6.c
> +++ b/drivers/pci/host/pci-imx6.c
> @@ -489,7 +489,7 @@ static int imx6_pcie_link_up(struct pcie_port *pp)
> * Wait a little bit, then re-check if the link finished
> * the training.
> */
> - usleep_range(1000, 2000);
> + mdelay(20);
> }
> /*
> * From L0, initiate MAC entry to gen2 if EP/RC supports gen2.
> --
> 1.8.4
>
^ permalink raw reply [flat|nested] 14+ messages in thread