Re: [PATCH 1/3] PCI: endpoint: Add RC-to-EP doorbell support using platform MSI controller

[Manivannan Sadhasivam]

On Sat, Sep 02, 2023 at 10:22:25AM +0530, Manivannan Sadhasivam wrote:
> On Wed, Apr 26, 2023 at 04:34:34PM -0400, Frank Li wrote:
> > This commit introduces a common method for sending messages from the Root Complex
> > (RC) to the Endpoint (EP) by utilizing the platform MSI interrupt controller,
> > such as ARM GIC, as an EP doorbell. Maps the memory assigned for the BAR region
> > by the PCI host to the message address of the platform MSI interrupt controller
> > in the PCI EP. As a result, when the PCI RC writes to the BAR region, it triggers
> > an IRQ at the EP. This implementation serves as a common method for all endpoint
> > function drivers.
> > 
> > However, it currently supports only one EP physical function due to limitations
> > in ARM MSI/IMS readiness.
> > 
> 
> I've provided generic comments below, but I will do one more thorough review
> after seeing epf-test driver patch.
> 
> > Signed-off-by: Frank Li <Frank.Li@xxxxxxx>
> > ---
> >  drivers/pci/endpoint/pci-epf-core.c | 109 ++++++++++++++++++++++++++++
> >  include/linux/pci-epf.h             |  16 ++++
> >  2 files changed, 125 insertions(+)
> > 
> > diff --git a/drivers/pci/endpoint/pci-epf-core.c b/drivers/pci/endpoint/pci-epf-core.c
> > index 355a6f56fcea..94ac82bf84c5 100644
> > --- a/drivers/pci/endpoint/pci-epf-core.c
> > +++ b/drivers/pci/endpoint/pci-epf-core.c
> > @@ -6,10 +6,12 @@
> >   * Author: Kishon Vijay Abraham I <kishon@xxxxxx>
> >   */
> >  
> > +#include <linux/irqreturn.h>
> 
> Why is this needed?
> 
> >  #include <linux/device.h>
> >  #include <linux/dma-mapping.h>
> >  #include <linux/slab.h>
> >  #include <linux/module.h>
> > +#include <linux/msi.h>
> >  
> >  #include <linux/pci-epc.h>
> >  #include <linux/pci-epf.h>
> > @@ -300,6 +302,113 @@ void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar,
> >  }
> >  EXPORT_SYMBOL_GPL(pci_epf_alloc_space);
> >  
> > +static enum irqreturn pci_epf_interrupt_handler(int irq, void *data)
> 
> static irqreturn_t
> 
> s/pci_epf_interrupt_handler/pci_epf_doorbell_handler
> 
> > +{
> > +	struct pci_epf *epf = data;
> > +
> > +	if (epf->event_ops && epf->event_ops->doorbell)
> > +		epf->event_ops->doorbell(epf, irq - epf->virq_base);
> > +
> > +	return IRQ_HANDLED;
> > +}
> > +
> > +static void pci_epf_write_msi_msg(struct msi_desc *desc, struct msi_msg *msg)
> > +{
> > +	struct pci_epc *epc = container_of(desc->dev, struct pci_epc, dev);
> > +	struct pci_epf *epf;
> > +
> > +	/* Todo: Need check correct epf if multi epf supported */
> > +	list_for_each_entry(epf, &epc->pci_epf, list) {
> > +		if (epf->msg && desc->msi_index < epf->num_msgs)
> > +			epf->msg[desc->msi_index] = *msg;
> > +	}
> > +}
> > +
> > +int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 num_msgs)
> > +{
> > +	struct irq_domain *domain;
> > +	struct pci_epc *epc;
> > +	struct device *dev;
> > +	int virq;
> > +	int ret;
> > +	int i;
> > +
> > +	epc = epf->epc;
> > +	dev = &epc->dev;
> 
> "epc_dev" to make it explicit
> 
> > +
> > +	/*
> > +	 * Current only support 1 function.
> 
> What does this mean exactly? Even a single EPC can support multiple EPFs
> 

Please ignore above comment.

- Mani

> > +	 * PCI IMS(interrupt message store) ARM support have not been
> > +	 * ready yet.
> 
> No need to mention platform irq controller name.
> 
> > +	 */
> > +	if (epc->function_num_map != 1)
> 
> Why can't you use, epf->func_no?
> 
> > +		return -EOPNOTSUPP;
> > +
> > +	domain = dev_get_msi_domain(dev->parent);
> > +	if (!domain)
> > +		return -EOPNTSUPP;
> 
> Newline
> 
> > +	dev_set_msi_domain(dev, domain);
> > +
> > +	/* use parent of_node to get device id information */
> > +	dev->of_node = dev->parent->of_node;
> > +
> 
> Why do you need of_node assignment inside EPF core?
> 
> > +	epf->msg = kcalloc(num_msgs, sizeof(struct msi_msg), GFP_KERNEL);
> > +	if (!epf->msg)
> > +		return -ENOMEM;
> > +
> > +	epf->num_msgs = num_msgs;
> > +
> 
> Move this to the start of the function, after checks.
> 
> > +	ret = platform_msi_domain_alloc_irqs(dev, num_msgs, pci_epf_write_msi_msg);
> > +	if (ret) {
> > +		dev_err(dev, "Can't allocate MSI from system MSI controller\n");
> 
> "Failed to allocate MSI"
> 
> > +		goto err_mem;
> 
> err_free_mem
> 
> > +	}
> > +
> > +	for (i = 0; i < num_msgs; i++) {
> > +		virq = msi_get_virq(dev, i);
> > +		if (i == 0)
> > +			epf->virq_base = virq;
> > +
> > +		ret = request_irq(virq, pci_epf_interrupt_handler, 0,
> > +				  "pci-epf-doorbell", epf);
> 
> IRQ name should have an index, otherwise all of them will have the same name.
> 
> > +
> > +		if (ret) {
> > +			dev_err(dev, "Failure request doorbell IRQ\n");
> 
> "Failed to request doorbell"
> 
> > +			goto err_irq;
> 
> err_free_irq
> 
> > +		}
> > +	}
> > +
> > +	epf->num_msgs = num_msgs;
> 
> Newline
> 
> > +	return ret;
> > +
> > +err_irq:
> > +	platform_msi_domain_free_irqs(dev);
> > +err_mem:
> > +	kfree(epf->msg);
> > +	epf->msg = NULL;
> > +	epf->num_msgs = 0;
> > +
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(pci_epf_alloc_doorbell);
> > +
> > +void pci_epf_free_doorbell(struct pci_epf *epf)
> > +{
> > +	struct pci_epc *epc;
> > +	int i;
> > +
> > +	epc = epf->epc;
> > +
> > +	for (i = 0; i < epf->num_msgs; i++)
> > +		free_irq(epf->virq_base + i, epf);
> > +
> > +	platform_msi_domain_free_irqs(&epc->dev);
> > +	kfree(epf->msg);
> > +	epf->msg = NULL;
> > +	epf->num_msgs = 0;
> > +}
> > +EXPORT_SYMBOL_GPL(pci_epf_free_doorbell);
> > +
> >  static void pci_epf_remove_cfs(struct pci_epf_driver *driver)
> >  {
> >  	struct config_group *group, *tmp;
> > diff --git a/include/linux/pci-epf.h b/include/linux/pci-epf.h
> > index b8441db2fa52..e187e3ee48d2 100644
> > --- a/include/linux/pci-epf.h
> > +++ b/include/linux/pci-epf.h
> > @@ -75,6 +75,7 @@ struct pci_epf_ops {
> >  struct pci_epc_event_ops {
> >  	int (*core_init)(struct pci_epf *epf);
> >  	int (*link_up)(struct pci_epf *epf);
> > +	int (*doorbell)(struct pci_epf *epf, int index);
> >  };
> >  
> >  /**
> > @@ -173,6 +174,9 @@ struct pci_epf {
> >  	unsigned long		vfunction_num_map;
> >  	struct list_head	pci_vepf;
> >  	const struct pci_epc_event_ops *event_ops;
> > +	struct msi_msg *msg;
> > +	u16 num_msgs;
> > +	int virq_base;
> >  };
> >  
> >  /**
> > @@ -216,4 +220,16 @@ int pci_epf_bind(struct pci_epf *epf);
> >  void pci_epf_unbind(struct pci_epf *epf);
> >  int pci_epf_add_vepf(struct pci_epf *epf_pf, struct pci_epf *epf_vf);
> >  void pci_epf_remove_vepf(struct pci_epf *epf_pf, struct pci_epf *epf_vf);
> > +int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 nums);
> > +void pci_epf_free_doorbell(struct pci_epf *epf);
> > +
> > +static inline struct msi_msg *epf_get_msg(struct pci_epf *epf)
> > +{
> > +	return epf->msg;
> > +}
> > +
> > +static inline u16 epf_get_msg_num(struct pci_epf *epf)
> > +{
> > +	return epf->num_msgs;
> > +}
> 
> I don't see a need for these two functions as they are doing just dereferences.
> 
> - Mani
> 
> >  #endif /* __LINUX_PCI_EPF_H */
> > -- 
> > 2.34.1
> > 
> 
> -- 
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