PCI: qcom: Ignore -ENODEV after Root Port reset

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

Posted by Konrad Dybcio 1 week, 1 day ago

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

Posted by Niklas Cassel 1 week, 1 day ago

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

Posted by Konrad Dybcio 1 week, 1 day ago

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

Posted by Niklas Cassel 1 week, 1 day ago

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

Posted by Krishna Chaitanya Chundru 1 week, 1 day ago


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,