linux-kernel - Re: [PATCH RFC v1 3/3] PCI: qcom: ep: Add wake up host op to dw_pcie_ep

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Date:   Tue, 27 Jun 2023 19:23:51 +0530
From:   Manivannan Sadhasivam <mani@...nel.org>
To:     Krishna Chaitanya Chundru <quic_krichai@...cinc.com>
Cc:     manivannan.sadhasivam@...aro.org, quic_vbadigan@...cinc.com,
        quic_ramkri@...cinc.com, linux-arm-msm@...r.kernel.org,
        konrad.dybcio@...aro.org,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "open list:PCIE ENDPOINT DRIVER FOR QUALCOMM" 
        <linux-pci@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC v1 3/3] PCI: qcom: ep: Add wake up host op to
 dw_pcie_ep_ops

On Mon, Jun 26, 2023 at 07:18:49PM +0530, Krishna Chaitanya Chundru wrote:
> 
> On 6/23/2023 11:48 AM, Manivannan Sadhasivam wrote:
> > On Wed, Jun 14, 2023 at 08:30:49PM +0530, Krishna chaitanya chundru wrote:
> > > Add wakeup host op to dw_pcie_ep_ops to wake up host from D3cold
> > > or D3hot.
> > > 
> > Commit message should describe how the wakeup is implemented in the driver.
> I will correct this in next series.
> > 
> > > Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
> > > ---
> > >   drivers/pci/controller/dwc/pcie-qcom-ep.c | 34 +++++++++++++++++++++++++++++++
> > >   1 file changed, 34 insertions(+)
> > > 
> > > diff --git a/drivers/pci/controller/dwc/pcie-qcom-ep.c b/drivers/pci/controller/dwc/pcie-qcom-ep.c
> > > index 5d146ec..916a138 100644
> > > --- a/drivers/pci/controller/dwc/pcie-qcom-ep.c
> > > +++ b/drivers/pci/controller/dwc/pcie-qcom-ep.c
> > > @@ -91,6 +91,7 @@
> > >   /* PARF_PM_CTRL register fields */
> > >   #define PARF_PM_CTRL_REQ_EXIT_L1		BIT(1)
> > >   #define PARF_PM_CTRL_READY_ENTR_L23		BIT(2)
> > > +#define PARF_PM_CTRL_XMT_PME			BIT(4)
> > >   #define PARF_PM_CTRL_REQ_NOT_ENTR_L1		BIT(5)
> > >   /* PARF_MHI_CLOCK_RESET_CTRL fields */
> > > @@ -794,10 +795,43 @@ static void qcom_pcie_ep_init(struct dw_pcie_ep *ep)
> > >   		dw_pcie_ep_reset_bar(pci, bar);
> > >   }
> > > +static int qcom_pcie_ep_wakeup_host(struct dw_pcie_ep *ep, u8 func_no)
> > > +{
> > > +	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> > > +	struct qcom_pcie_ep *pcie_ep = to_pcie_ep(pci);
> > > +	struct device *dev = pci->dev;
> > > +	u32 perst, dstate, val;
> > > +
> > > +	perst = gpiod_get_value(pcie_ep->reset);
> > > +	/* Toggle wake GPIO when device is in D3 cold */
> > > +	if (perst) {
> > > +		dev_info(dev, "Device is in D3 cold toggling wake\n");
> > dev_dbg(). "Waking up the host by toggling WAKE#"
> > 
> > > +		gpiod_set_value_cansleep(pcie_ep->wake, 1);
> > Waking a device from D3cold requires power-on sequence by the host and in the
> > presence of Vaux, the EPF should be prepared for that. In that case, the mode of
> > wakeup should be decided by the EPF driver. So the wakeup API should have an
> > argument to decide whether the wakeup is through PME or sideband WAKE#.
> > 
> > Also note that as per PCIe Spec 3.0, the devices can support PME generation from
> > D3cold provided that the Vaux is supplied to the device. I do not know if that
> > is supported by Qcom devices but API should honor the spec. So the wakeup
> > control should come from EPF driver as I suggested above.
> 
> I aggre with you, but how will EPF know the PCI device state is in D3cold or
> D3hot.
> 

We should add a notifier in the controller driver which signals EPF when it
receives the DState events.. Take a look at pci_epc_linkdown().

> And how the EPF knows whether Vaux is supported or not in D3cold?
> 
> If there is any existing mechanism can you please point me that.
> 
> FYI Qcom does not support vaux power in D3 cold.
> 

If the EPF can trigger wakeup event during D3Cold then it means it is powered
by Vaux, isn't it?

- Mani

> > > +		usleep_range(WAKE_DELAY_US, WAKE_DELAY_US + 500);
> > > +		gpiod_set_value_cansleep(pcie_ep->wake, 0);
> > > +		return 0;
> > > +	}
> > > +
> > > +	dstate = dw_pcie_readl_dbi(pci, DBI_CON_STATUS) &
> > > +				   DBI_CON_STATUS_POWER_STATE_MASK;
> > > +	if (dstate == 3) {
> > > +		dev_info(dev, "Device is in D3 hot sending inband PME\n");
> > dev_dbg(). As I said, the device can sent PME from D3cold also. So the log could
> > be "Waking up the host using PME".
> > 
> > > +		val = readl_relaxed(pcie_ep->parf + PARF_PM_CTRL);
> > > +		val |= PARF_PM_CTRL_XMT_PME;
> > > +		writel_relaxed(val, pcie_ep->parf + PARF_PM_CTRL);
> > > +	} else {
> > > +		dev_err(dev, "Device is not in D3 state wakeup is not supported\n");
> > > +		return -EPERM;
> > -ENOTSUPP
> > 
> > - Mani
> > 
> > > +	}
> > > +
> > > +	return 0;
> > > +}
> > > +
> > >   static const struct dw_pcie_ep_ops pci_ep_ops = {
> > >   	.ep_init = qcom_pcie_ep_init,
> > >   	.raise_irq = qcom_pcie_ep_raise_irq,
> > >   	.get_features = qcom_pcie_epc_get_features,
> > > +	.wakeup_host = qcom_pcie_ep_wakeup_host,
> > >   };
> > >   static int qcom_pcie_ep_probe(struct platform_device *pdev)
> > > -- 
> > > 2.7.4
> > > 

-- 
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