On 29.03.2023 14:52, Manivannan Sadhasivam wrote:
> On Wed, Mar 29, 2023 at 11:56:43AM +0200, Johan Hovold wrote:
>> On Mon, Mar 27, 2023 at 07:08:24PM +0530, Manivannan Sadhasivam wrote:
>>> During the system suspend, vote for minimal interconnect bandwidth and
>>> also turn OFF the resources like clock and PHY if there are no active
>>> devices connected to the controller. For the controllers with active
>>> devices, the resources are kept ON as removing the resources will
>>> trigger access violation during the late end of suspend cycle as kernel
>>> tries to access the config space of PCIe devices to mask the MSIs.
>>>
>>> Also, it is not desirable to put the link into L2/L3 state as that
>>> implies VDD supply will be removed and the devices may go into powerdown
>>> state. This will affect the lifetime of storage devices like NVMe.
>>>
>>> And finally, during resume, turn ON the resources if the controller was
>>> truly suspended (resources OFF) and update the interconnect bandwidth
>>> based on PCIe Gen speed.
>>>
>>> Suggested-by: Krishna chaitanya chundru <quic_krichai@xxxxxxxxxxx>
>>> Acked-by: Dhruva Gole <d-gole@xxxxxx>
>>> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
>>> ---
>>> drivers/pci/controller/dwc/pcie-qcom.c | 62 ++++++++++++++++++++++++++
>>> 1 file changed, 62 insertions(+)
>>>
>>> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
>>> index a232b04af048..f33df536d9be 100644
>>> --- a/drivers/pci/controller/dwc/pcie-qcom.c
>>> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
>>> @@ -227,6 +227,7 @@ struct qcom_pcie {
>>> struct gpio_desc *reset;
>>> struct icc_path *icc_mem;
>>> const struct qcom_pcie_cfg *cfg;
>>> + bool suspended;
>>> };
>>>
>>> #define to_qcom_pcie(x) dev_get_drvdata((x)->dev)
>>> @@ -1820,6 +1821,62 @@ static int qcom_pcie_probe(struct platform_device *pdev)
>>> return ret;
>>> }
>>>
>>> +static int qcom_pcie_suspend_noirq(struct device *dev)
>>> +{
>>> + struct qcom_pcie *pcie = dev_get_drvdata(dev);
>>> + int ret;
>>> +
>>> + /*
>>> + * Set minimum bandwidth required to keep data path functional during
>>> + * suspend.
>>> + */
>>> + ret = icc_set_bw(pcie->icc_mem, 0, MBps_to_icc(250));
>>
>> This isn't really the minimum bandwidth you're setting here.
>>
>> I think you said off list that you didn't see real impact reducing the
>> bandwidth, but have you tried requesting the real minimum which would be
>> kBps_to_icc(1)?
>>
>> Doing so works fine here with both the CRD and X13s and may result in
>> some further power savings.
>>
>
> No, we shouldn't be setting random value as the bandwidth. Reason is, these
> values are computed by the bus team based on the requirement of the interconnect
> paths (clock, voltage etc...) with actual PCIe Gen speeds.
Should it then be variable, based on the current link gen?
Konrad
I don't know about
> the potential implication even if it happens to work.
>
> - Mani
>
>>> + if (ret) {
>>> + dev_err(dev, "Failed to set interconnect bandwidth: %d\n", ret);
>>> + return ret;
>>> + }
>>
>> Johan
>
