linux-kernel - Re: [PATCH v7 2/4] PCI: qcom-ep: Add support for D-state change notification

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Message-ID: <20240710121118.GA240905@bhelgaas>
Date: Wed, 10 Jul 2024 07:11:18 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Krishna chaitanya chundru <quic_krichai@...cinc.com>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Jonathan Corbet <corbet@....net>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Rob Herring <robh@...nel.org>, linux-pci@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org, mhi@...ts.linux.dev,
	quic_vbadigan@...cinc.com, quic_ramkri@...cinc.com,
	quic_nitegupt@...cinc.com, quic_skananth@...cinc.com,
	quic_parass@...cinc.com, Manivannan Sadhasivam <mani@...nel.org>
Subject: Re: [PATCH v7 2/4] PCI: qcom-ep: Add support for D-state change
 notification

On Wed, Jul 10, 2024 at 04:38:15PM +0530, Krishna chaitanya chundru wrote:
> Add support to pass D-state change notification to Endpoint
> function driver.

Blank line between paragraphs.

> Read perst value to determine if the link is in D3Cold/D3hot.

I assume this reads the state of the PERST# signal driven by the host.
Style it to match the spec usage ("PERST#") to make that connection
clearer.

D3cold/D3hot is a device state and doesn't apply to a link.  Link
states are L0, L1, L2, L3,etc.  Also in cover letter.

I don't understand the connection between PERST# state and the device
D state.  D3cold is defined to mean main power is absent.  Is the
endpoint firmware still running when main power is absent?

> Reviewed-by: Manivannan Sadhasivam <mani@...nel.org>
> Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
> ---
>  drivers/pci/controller/dwc/pcie-qcom-ep.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-qcom-ep.c b/drivers/pci/controller/dwc/pcie-qcom-ep.c
> index 236229f66c80..817fad805c51 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom-ep.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom-ep.c
> @@ -648,6 +648,7 @@ static irqreturn_t qcom_pcie_ep_global_irq_thread(int irq, void *data)
>  	struct device *dev = pci->dev;
>  	u32 status = readl_relaxed(pcie_ep->parf + PARF_INT_ALL_STATUS);
>  	u32 mask = readl_relaxed(pcie_ep->parf + PARF_INT_ALL_MASK);
> +	pci_power_t state;
>  	u32 dstate, val;
>  
>  	writel_relaxed(status, pcie_ep->parf + PARF_INT_ALL_CLEAR);
> @@ -671,11 +672,16 @@ static irqreturn_t qcom_pcie_ep_global_irq_thread(int irq, void *data)
>  		dstate = dw_pcie_readl_dbi(pci, DBI_CON_STATUS) &
>  					   DBI_CON_STATUS_POWER_STATE_MASK;
>  		dev_dbg(dev, "Received D%d state event\n", dstate);
> -		if (dstate == 3) {
> +		state = dstate;
> +		if (dstate == PCI_D3hot) {
>  			val = readl_relaxed(pcie_ep->parf + PARF_PM_CTRL);
>  			val |= PARF_PM_CTRL_REQ_EXIT_L1;
>  			writel_relaxed(val, pcie_ep->parf + PARF_PM_CTRL);
> +
> +			if (gpiod_get_value(pcie_ep->reset))
> +				state = PCI_D3cold;
>  		}
> +		pci_epc_dstate_notify(pci->ep.epc, state);
>  	} else if (FIELD_GET(PARF_INT_ALL_LINK_UP, status)) {
>  		dev_dbg(dev, "Received Linkup event. Enumeration complete!\n");
>  		dw_pcie_ep_linkup(&pci->ep);
> 
> -- 
> 2.42.0
>