Re: [PATCH v7 09/13] PCI: tegra194: Allow system suspend when the Endpoint link is not up

[Manikanta Maddireddy <mmaddireddy@nvidia.com>]

On 05/03/26 3:59 pm, Manivannan Sadhasivam wrote:
> On Tue, Mar 03, 2026 at 12:24:44PM +0530, Manikanta Maddireddy wrote:
>> From: Vidya Sagar <vidyas@nvidia.com>
>>
>> Only a Root Port initiates the L2 sequence. PCIe link is kept in L2 state
> 
> It is not Root Port, it is the host software which initiates the L2 entry
> sequence.
> 
> And L2 is only guaranteed if the Vaux is available.
> 
I will fix the commit message.

>> during suspend. If Endpoint mode is enabled and the link is up, the
>> software cannot proceed with suspend. However, when the PCIe Endpoint
>> driver is probed, but the PCIe link is not up, Tegra can go into suspend
>> state. So, allow system to suspend in this case.
>>
>> Fixes: de2bbf2b71bb ("PCI: tegra194: Don't allow suspend when Tegra PCIe is in EP mode")
>> Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
>> Tested-by: Jon Hunter <jonathanh@nvidia.com>
>> Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
>> Signed-off-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
>> ---
>> Changes V1 -> V7: None
>>
>>   drivers/pci/controller/dwc/pcie-tegra194.c | 31 +++++++++++++++++-----
>>   1 file changed, 25 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
>> index 5b79d3c28ba6..b2794be35cfe 100644
>> --- a/drivers/pci/controller/dwc/pcie-tegra194.c
>> +++ b/drivers/pci/controller/dwc/pcie-tegra194.c
>> @@ -2267,16 +2267,28 @@ static void tegra_pcie_dw_remove(struct platform_device *pdev)
>>   		gpiod_set_value(pcie->pex_refclk_sel_gpiod, 0);
>>   }
>>   
>> -static int tegra_pcie_dw_suspend_late(struct device *dev)
>> +static int tegra_pcie_dw_suspend(struct device *dev)
>>   {
>>   	struct tegra_pcie_dw *pcie = dev_get_drvdata(dev);
>> -	u32 val;
>>   
>>   	if (pcie->of_data->mode == DW_PCIE_EP_TYPE) {
>> -		dev_err(dev, "Failed to Suspend as Tegra PCIe is in EP mode\n");
>> -		return -EPERM;
>> +		if (pcie->ep_state == EP_STATE_ENABLED) {
>> +			dev_err(dev, "Tegra PCIe is in EP mode, suspend not allowed\n");
>> +			return -EPERM;
>> +		}
>> +
>> +		disable_irq(pcie->pex_rst_irq);
> 
> So you just disable PERST# IRQ during suspend? And even if the host deasserts
> PERST#, EP is not going to wakeup?
> 
> Technically it is possible that whenever the EP wakes up, it will see PERST# IRQ
> since PERST# is level triggered, but it just sounds dumb to let the endpoint
> sleep after host deasserting PERST#.
> 
> - Mani
> 
I need to check if PERST# line in Tegra has wake feature and 
corresponding PMC changes are available. Anyway adding wake feature will 
be separate patch. In this current patch, I am trying to reduce the 
impact of Endpoint on suspend. If Endpoint is never initialized I don't 
see a reason to block suspend. Are you OK with this current patch to 
reduce the impact on suspend? Or do you have any suggestions?

- Manikanta

-- 
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