[PATCH] PCI: qcom: Ignore -ENODEV after Root Port reset

[PATCH] PCI: qcom: Ignore -ENODEV after Root Port reset

[Konrad Dybcio]

Root Port recovery may race with a device hot-unplug. In that case,
dw_pcie_wait_for_link() returns -ENODEV because no device is detected
after the controller has been successfully reset.

This is a valid outcome and should not cause Root Port recovery to
fail. Ignore -ENODEV while continuing to propagate other link-training
errors.

Assisted-by: LLM
Fixes: 4d88cb82a6d9 ("PCI: qcom: Implement .reset_root_port() and use for link down")
Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
---
 drivers/pci/controller/dwc/pcie-qcom.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index ee63a6ec99de4d07c16b8d6cb68df0d92f822cd8..3d3be9bf798b7c247d69969d6570385b8648123f 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -1880,6 +1880,9 @@ static int qcom_pcie_reset_root_port(struct pci_host_bridge *bridge,
 	qcom_pcie_start_link(pci);
 
 	ret = dw_pcie_wait_for_link(pci);
+	/* This linkdown might have been a hot-unplug */
+	if (ret == -ENODEV)
+		ret = 0;
 	if (ret)
 		return ret;
 

---
base-commit: e6e35979777d646fe3c7c94dca7dd32fb25d45f4
change-id: 20260916-topic-pcie_portrec_enodev-cc576ea927f9

Best regards,
-- 
Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>

Re: [PATCH] PCI: qcom: Ignore -ENODEV after Root Port reset

[sashiko-bot]

> Root Port recovery may race with a device hot-unplug. In that case,
> dw_pcie_wait_for_link() returns -ENODEV because no device is detected
> after the controller has been successfully reset.
> 
> This is a valid outcome and should not cause Root Port recovery to
> fail. Ignore -ENODEV while continuing to propagate other link-training
> errors.
> 
> Assisted-by: LLM
> Fixes: 4d88cb82a6d9 ("PCI: qcom: Implement .reset_root_port() and use for link down")
> Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260916-topic-pcie_portrec_enodev-v1-1-5dc7bde39552@oss.qualcomm.com?part=1

Re: [PATCH] PCI: qcom: Ignore -ENODEV after Root Port reset

[Krishna Chaitanya Chundru]

On 9/16/2026 6:07 PM, Konrad Dybcio wrote:
> Root Port recovery may race with a device hot-unplug. In that case,
> dw_pcie_wait_for_link() returns -ENODEV because no device is detected
> after the controller has been successfully reset.
>
> This is a valid outcome and should not cause Root Port recovery to
> fail. Ignore -ENODEV while continuing to propagate other link-training
> errors.
>
> Assisted-by: LLM
> Fixes: 4d88cb82a6d9 ("PCI: qcom: Implement .reset_root_port() and use for link down")
> Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>

Reviewed-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>

- Krishna Chaitanya.

> ---
>  drivers/pci/controller/dwc/pcie-qcom.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index ee63a6ec99de4d07c16b8d6cb68df0d92f822cd8..3d3be9bf798b7c247d69969d6570385b8648123f 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -1880,6 +1880,9 @@ static int qcom_pcie_reset_root_port(struct pci_host_bridge *bridge,
>  	qcom_pcie_start_link(pci);
>  
>  	ret = dw_pcie_wait_for_link(pci);
> +	/* This linkdown might have been a hot-unplug */
> +	if (ret == -ENODEV)
> +		ret = 0;
>  	if (ret)
>  		return ret;
>  
>
> ---
> base-commit: e6e35979777d646fe3c7c94dca7dd32fb25d45f4
> change-id: 20260916-topic-pcie_portrec_enodev-cc576ea927f9
>
> Best regards,

Re: [PATCH] PCI: qcom: Ignore -ENODEV after Root Port reset

[Niklas Cassel]

Hello Konrad,

On Wed, Sep 16, 2026 at 02:37:49PM +0200, Konrad Dybcio wrote:
> Root Port recovery may race with a device hot-unplug. In that case,
> dw_pcie_wait_for_link() returns -ENODEV because no device is detected
> after the controller has been successfully reset.
> 
> This is a valid outcome and should not cause Root Port recovery to
> fail. Ignore -ENODEV while continuing to propagate other link-training
> errors.
> 
> Assisted-by: LLM
> Fixes: 4d88cb82a6d9 ("PCI: qcom: Implement .reset_root_port() and use for link down")
> Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
> ---
>  drivers/pci/controller/dwc/pcie-qcom.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index ee63a6ec99de4d07c16b8d6cb68df0d92f822cd8..3d3be9bf798b7c247d69969d6570385b8648123f 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -1880,6 +1880,9 @@ static int qcom_pcie_reset_root_port(struct pci_host_bridge *bridge,
>  	qcom_pcie_start_link(pci);
>  
>  	ret = dw_pcie_wait_for_link(pci);
> +	/* This linkdown might have been a hot-unplug */
> +	if (ret == -ENODEV)
> +		ret = 0;
>  	if (ret)
>  		return ret;


I did not know that pcie-qcom supported hotplug.

Last when I was discussing this with Mani, I'm quite sure that he said that
it doesn't, see:
https://lore.kernel.org/all/20251222064207.3246632-8-cassel@kernel.org/

If that is the case, perhaps the commit message and code comment should be
clarified, so it is more clear what it actually means.


Kind regards,
Niklas

Re: [PATCH] PCI: qcom: Ignore -ENODEV after Root Port reset

[Konrad Dybcio]

On 9/16/26 5:53 PM, Niklas Cassel wrote:
> Hello Konrad,
> 
> On Wed, Sep 16, 2026 at 02:37:49PM +0200, Konrad Dybcio wrote:
>> Root Port recovery may race with a device hot-unplug. In that case,
>> dw_pcie_wait_for_link() returns -ENODEV because no device is detected
>> after the controller has been successfully reset.
>>
>> This is a valid outcome and should not cause Root Port recovery to
>> fail. Ignore -ENODEV while continuing to propagate other link-training
>> errors.
>>
>> Assisted-by: LLM
>> Fixes: 4d88cb82a6d9 ("PCI: qcom: Implement .reset_root_port() and use for link down")
>> Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
>> ---
>>  drivers/pci/controller/dwc/pcie-qcom.c | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
>> index ee63a6ec99de4d07c16b8d6cb68df0d92f822cd8..3d3be9bf798b7c247d69969d6570385b8648123f 100644
>> --- a/drivers/pci/controller/dwc/pcie-qcom.c
>> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
>> @@ -1880,6 +1880,9 @@ static int qcom_pcie_reset_root_port(struct pci_host_bridge *bridge,
>>  	qcom_pcie_start_link(pci);
>>  
>>  	ret = dw_pcie_wait_for_link(pci);
>> +	/* This linkdown might have been a hot-unplug */
>> +	if (ret == -ENODEV)
>> +		ret = 0;
>>  	if (ret)
>>  		return ret;
> 
> 
> I did not know that pcie-qcom supported hotplug.
> 
> Last when I was discussing this with Mani, I'm quite sure that he said that
> it doesn't, see:
> https://lore.kernel.org/all/20251222064207.3246632-8-cassel@kernel.org/

I don't know if native ports still don't, but the ones used for USB4
tunneling certainly do

see e.g.:
65ccb2203ef8 ("PCI: qcom: Clear Attention Button Present in Slot Capabilities")

Konrad

Re: [PATCH] PCI: qcom: Ignore -ENODEV after Root Port reset

[Niklas Cassel]

On Wed, Sep 16, 2026 at 06:13:29PM +0200, Konrad Dybcio wrote:
> On 9/16/26 5:53 PM, Niklas Cassel wrote:
> > Hello Konrad,
> > 
> > On Wed, Sep 16, 2026 at 02:37:49PM +0200, Konrad Dybcio wrote:
> >> Root Port recovery may race with a device hot-unplug. In that case,
> >> dw_pcie_wait_for_link() returns -ENODEV because no device is detected
> >> after the controller has been successfully reset.
> >>
> >> This is a valid outcome and should not cause Root Port recovery to
> >> fail. Ignore -ENODEV while continuing to propagate other link-training
> >> errors.
> >>
> >> Assisted-by: LLM
> >> Fixes: 4d88cb82a6d9 ("PCI: qcom: Implement .reset_root_port() and use for link down")
> >> Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
> >> ---
> >>  drivers/pci/controller/dwc/pcie-qcom.c | 3 +++
> >>  1 file changed, 3 insertions(+)
> >>
> >> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> >> index ee63a6ec99de4d07c16b8d6cb68df0d92f822cd8..3d3be9bf798b7c247d69969d6570385b8648123f 100644
> >> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> >> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> >> @@ -1880,6 +1880,9 @@ static int qcom_pcie_reset_root_port(struct pci_host_bridge *bridge,
> >>  	qcom_pcie_start_link(pci);
> >>  
> >>  	ret = dw_pcie_wait_for_link(pci);
> >> +	/* This linkdown might have been a hot-unplug */
> >> +	if (ret == -ENODEV)
> >> +		ret = 0;
> >>  	if (ret)
> >>  		return ret;
> > 
> > 
> > I did not know that pcie-qcom supported hotplug.
> > 
> > Last when I was discussing this with Mani, I'm quite sure that he said that
> > it doesn't, see:
> > https://lore.kernel.org/all/20251222064207.3246632-8-cassel@kernel.org/
> 
> I don't know if native ports still don't, but the ones used for USB4
> tunneling certainly do
> 
> see e.g.:
> 65ccb2203ef8 ("PCI: qcom: Clear Attention Button Present in Slot Capabilities")

Ok, nice to see :)


Kind regards,
Niklas

Re: [PATCH] PCI: qcom: Ignore -ENODEV after Root Port reset

[Manivannan Sadhasivam]

On 2026-09-16 17:53 +0200, Niklas Cassel wrote:
> Hello Konrad,
> 
> On Wed, Sep 16, 2026 at 02:37:49PM +0200, Konrad Dybcio wrote:
> > Root Port recovery may race with a device hot-unplug. In that case,
> > dw_pcie_wait_for_link() returns -ENODEV because no device is detected
> > after the controller has been successfully reset.
> > 
> > This is a valid outcome and should not cause Root Port recovery to
> > fail. Ignore -ENODEV while continuing to propagate other link-training
> > errors.
> > 
> > Assisted-by: LLM
> > Fixes: 4d88cb82a6d9 ("PCI: qcom: Implement .reset_root_port() and use for link down")
> > Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
> > ---
> >  drivers/pci/controller/dwc/pcie-qcom.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> > index ee63a6ec99de4d07c16b8d6cb68df0d92f822cd8..3d3be9bf798b7c247d69969d6570385b8648123f 100644
> > --- a/drivers/pci/controller/dwc/pcie-qcom.c
> > +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> > @@ -1880,6 +1880,9 @@ static int qcom_pcie_reset_root_port(struct pci_host_bridge *bridge,
> >  	qcom_pcie_start_link(pci);
> >  
> >  	ret = dw_pcie_wait_for_link(pci);
> > +	/* This linkdown might have been a hot-unplug */
> > +	if (ret == -ENODEV)
> > +		ret = 0;
> >  	if (ret)
> >  		return ret;
> 
> 
> I did not know that pcie-qcom supported hotplug.
> 
> Last when I was discussing this with Mani, I'm quite sure that he said that
> it doesn't, see:
> https://lore.kernel.org/all/20251222064207.3246632-8-cassel@kernel.org/
> 

That was my understanding at that time as the hotplug command completions were
getting timedout even though the RP claimed that it supported hotplug:

pcieport 0001:00:00.0: pciehp: Timeout on hotplug command 0x03c0 (issued 2020 msec ago)

Then I asked around internally within Qcom and they claimed that nobody tested
hotplug on Qcom SoCs as the usecases were mostly mobile at that time (soldered
EPs), so hotplug may not work and we should not claim it to be supported.

So I went ahead and disabled hotplug capability of the RPs with:
a54db86ddc153 ("PCI: qcom: Do not advertise hotplug capability for IPs v2.7.0
and v1.9.0")

Then after some time, we started getting form factors with hotpluggable slots
and when we tested hotplug with the above commit reverted, it actually worked,
despite the command completion timeouts. So we finally added hotplug capability
back with:

33a76fc3c3e6 ("PCI: qcom: Advertise Hotplug Slot Capability with no Command
Completion support")

- Mani

Re: [PATCH] PCI: qcom: Ignore -ENODEV after Root Port reset

[Manivannan Sadhasivam]

On Wed, 16 Sep 2026 14:37:49 +0200, Konrad Dybcio wrote:
> PCI: qcom: Ignore -ENODEV after Root Port reset

Applied, thanks!

[1/1] PCI: qcom: Ignore -ENODEV after Root Port reset
      commit: 78f27ea27d9870806f51b6f44db7ef6df62f7891

Best regards,
-- 
மணிவண்ணன் சதாசிவம்