linux-kernel - Re: [PATCH RFC v1 1/3] PCI: endpoint: Add wakeup host API to EPC core

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Message-ID: <791ced92-6198-3b6b-3cb8-c6f413986f61@amd.com>
Date:   Mon, 19 Jun 2023 14:52:40 +0530
From:   Kishon Vijay Abraham I <kvijayab@....com>
To:     Krishna chaitanya chundru <quic_krichai@...cinc.com>,
        manivannan.sadhasivam@...aro.org
Cc:     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>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "open list:PCI ENDPOINT SUBSYSTEM" <linux-pci@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC v1 1/3] PCI: endpoint: Add wakeup host API to EPC core

Hi Krishna,

On 6/14/2023 8:30 PM, Krishna chaitanya chundru wrote:
> Endpoint cannot send any data/MSI when the device state is in
> D3cold or D3hot. Endpoint needs to bring the device back to D0
> to send any kind of data.
> 
> For this endpoint can send inband PME the device is in D3hot or
> toggle wake when the device is D3 cold.
> 
> To support this adding wake up host to epc core.
> 
> Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
> ---
>   drivers/pci/endpoint/pci-epc-core.c | 29 +++++++++++++++++++++++++++++
>   include/linux/pci-epc.h             |  3 +++
>   2 files changed, 32 insertions(+)
> 
> diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
> index 46c9a5c..d203947 100644
> --- a/drivers/pci/endpoint/pci-epc-core.c
> +++ b/drivers/pci/endpoint/pci-epc-core.c
> @@ -167,6 +167,35 @@ const struct pci_epc_features *pci_epc_get_features(struct pci_epc *epc,
>   EXPORT_SYMBOL_GPL(pci_epc_get_features);
>   
>   /**
> + * pci_epc_wakeup_host() - interrupt the host system
> + * @epc: the EPC device which has to interrupt the host
> + * @func_no: the physical endpoint function number in the EPC device
> + * @vfunc_no: the virtual endpoint function number in the physical function
> + *
> + * Invoke to wakeup host
> + */
> +int pci_epc_wakeup_host(struct pci_epc *epc, u8 func_no, u8 vfunc_no)
> +{
> +	int ret;
> +
> +	if (IS_ERR_OR_NULL(epc) || func_no >= epc->max_functions)
> +		return -EINVAL;
> +
> +	if (vfunc_no > 0 && (!epc->max_vfs || vfunc_no > epc->max_vfs[func_no]))
> +		return -EINVAL;
> +
> +	if (!epc->ops->wakeup_host)
> +		return 0;
> +
> +	mutex_lock(&epc->lock);
> +	ret = epc->ops->wakeup_host(epc, func_no, vfunc_no);
> +	mutex_unlock(&epc->lock);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(pci_epc_wakeup_host);

Which endpoint function driver uses this? And when does it have to be used?

Update Documentation for any new API's here
Documentation/PCI/endpoint/pci-endpoint.rst

Thanks,
Kishon
> +
> +/**
>    * pci_epc_stop() - stop the PCI link
>    * @epc: the link of the EPC device that has to be stopped
>    *
> diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h
> index 301bb0e..a8496be 100644
> --- a/include/linux/pci-epc.h
> +++ b/include/linux/pci-epc.h
> @@ -59,6 +59,7 @@ pci_epc_interface_string(enum pci_epc_interface_type type)
>    * @start: ops to start the PCI link
>    * @stop: ops to stop the PCI link
>    * @get_features: ops to get the features supported by the EPC
> + * @wakeup_host: ops to wakeup the host
>    * @owner: the module owner containing the ops
>    */
>   struct pci_epc_ops {
> @@ -88,6 +89,7 @@ struct pci_epc_ops {
>   	void	(*stop)(struct pci_epc *epc);
>   	const struct pci_epc_features* (*get_features)(struct pci_epc *epc,
>   						       u8 func_no, u8 vfunc_no);
> +	int	(*wakeup_host)(struct pci_epc *epc, u8 func_no, u8 vfunc_no);
>   	struct module *owner;
>   };
>   
> @@ -232,6 +234,7 @@ int pci_epc_start(struct pci_epc *epc);
>   void pci_epc_stop(struct pci_epc *epc);
>   const struct pci_epc_features *pci_epc_get_features(struct pci_epc *epc,
>   						    u8 func_no, u8 vfunc_no);
> +int pci_epc_wakeup_host(struct pci_epc *epc, u8 func_no, u8 vfunc_no);
>   enum pci_barno
>   pci_epc_get_first_free_bar(const struct pci_epc_features *epc_features);
>   enum pci_barno pci_epc_get_next_free_bar(const struct pci_epc_features