Date:   Fri, 17 Jun 2022 16:44:27 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     <ira.weiny@...el.com>, Dan Williams <dan.j.williams@...el.com>,
        "Bjorn Helgaas" <bhelgaas@...gle.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>
CC:     Ira Weiny <ira.weiny@...el.com>,
        Ben Widawsky <bwidawsk@...nel.org>,
        Alison Schofield <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        <linux-kernel@...r.kernel.org>, <linux-cxl@...r.kernel.org>,
        <linux-pci@...r.kernel.org>
Subject: RE: [PATCH V11 4/8] cxl/pci: Create PCI DOE mailbox's for memory
 devices

ira.weiny@ wrote:
> From: Ira Weiny <ira.weiny@...el.com>
> 
> DOE mailbox objects will be needed for various mailbox communications
> with each memory device.
> 
> Iterate each DOE mailbox capability and create PCI DOE mailbox objects
> as found.
> 
> It is not anticipated that this is the final resting place for the
> iteration of the DOE devices.  The support of ports may drive this code
> into the pcie side.  In this imagined architecture the CXL port driver
> would then query into the PCI device for the DOE mailbox array.
> 
> For now this is good enough for the endpoints and the split is similar
> to the envisioned architecture where getting the mailbox array is
> separated from the various protocol needs.  For example, it is not
> anticipated that the CDAT code will need to move because it is only
> needed by the cxl_ports.
> 
> Likewise irq's are separated out in a similar design pattern to the
> PCIe port driver.  But a much simpler irq enabling flag is used and only
> DOE interrupts are supported.
> 
> Reviewed-by: Ben Widawsky <bwidawsk@...nel.org>
> Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> 
> ---
> Changes from V9:
> 	Bug fix: ensure DOE mailboxes are iterated before memdev add
> 	Ben Widawsky
> 		Set use_irq to false and just return on error.
> 		Don't return a value from devm_cxl_pci_create_doe()
> 		Skip allocating doe_mb array if there are no mailboxes
> 		Skip requesting irqs if none found.
> 	Ben/Jonathan Cameron
> 		s/num_irqs/max_irqs
> 
> Changes from V8:
> 	Move PCI_DOE selection to CXL_BUS to support future patches
> 	which move queries into the port code.
> 	Remove Auxiliary device arch
> 	Squash the functionality of the auxiliary driver into this
> 	patch.
> 	Split out the irq handling a bit.
> 
> Changes from V7:
> 	Minor code clean ups
> 	Rebased on cxl-pending
> 
> Changes from V6:
> 	Move all the auxiliary device stuff to the CXL layer
> 
> Changes from V5:
> 	Split the CXL specific stuff off from the PCI DOE create
> 	auxiliary device code.
> ---
>  drivers/cxl/Kconfig  |   1 +
>  drivers/cxl/cxlmem.h |   6 +++
>  drivers/cxl/pci.c    | 114 +++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 121 insertions(+)
> 
> diff --git a/drivers/cxl/Kconfig b/drivers/cxl/Kconfig
> index f64e3984689f..7adaaf80b302 100644
> --- a/drivers/cxl/Kconfig
> +++ b/drivers/cxl/Kconfig
> @@ -2,6 +2,7 @@
>  menuconfig CXL_BUS
>  	tristate "CXL (Compute Express Link) Devices Support"
>  	depends on PCI
> +	select PCI_DOE
>  	help
>  	  CXL is a bus that is electrically compatible with PCI Express, but
>  	  layers three protocols on that signalling (CXL.io, CXL.cache, and
> diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
> index 60d10ee1e7fc..4d2764b865ab 100644
> --- a/drivers/cxl/cxlmem.h
> +++ b/drivers/cxl/cxlmem.h
> @@ -191,6 +191,8 @@ struct cxl_endpoint_dvsec_info {
>   * @component_reg_phys: register base of component registers
>   * @info: Cached DVSEC information about the device.
>   * @serial: PCIe Device Serial Number
> + * @doe_mbs: PCI DOE mailbox array
> + * @num_mbs: Number of DOE mailboxes
>   * @mbox_send: @dev specific transport for transmitting mailbox commands
>   *
>   * See section 8.2.9.5.2 Capacity Configuration and Label Storage for
> @@ -224,6 +226,10 @@ struct cxl_dev_state {
>  	resource_size_t component_reg_phys;
>  	u64 serial;
>  
> +	bool doe_use_irq;

Don't pass temporary state through a long lived data structure. Just
pass flag by reference between the functions that want to coordinate
this.


> +	struct pci_doe_mb **doe_mbs;
> +	int num_mbs;
> +
>  	int (*mbox_send)(struct cxl_dev_state *cxlds, struct cxl_mbox_cmd *cmd);
>  };
>  
> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> index 5a0ae46d4989..72c7b535f5df 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/pci.c
> @@ -8,6 +8,7 @@
>  #include <linux/mutex.h>
>  #include <linux/list.h>
>  #include <linux/pci.h>
> +#include <linux/pci-doe.h>
>  #include <linux/io.h>
>  #include "cxlmem.h"
>  #include "cxlpci.h"
> @@ -386,6 +387,116 @@ static int cxl_setup_regs(struct pci_dev *pdev, enum cxl_regloc_type type,
>  	return rc;
>  }
>  
> +static void cxl_pci_free_irq_vectors(void *data)
> +{
> +	pci_free_irq_vectors(data);
> +}
> +
> +static void cxl_doe_destroy_mb(void *ds)
> +{
> +	struct cxl_dev_state *cxlds = ds;
> +	int i;
> +
> +	for (i = 0; i < cxlds->num_mbs; i++) {
> +		if (cxlds->doe_mbs[i])
> +			pci_doe_destroy_mb(cxlds->doe_mbs[i]);
> +	}
> +}
> +
> +static void cxl_alloc_irq_vectors(struct cxl_dev_state *cxlds)
> +{
> +	struct device *dev = cxlds->dev;
> +	struct pci_dev *pdev = to_pci_dev(dev);
> +	int max_irqs = 0;
> +	int off = 0;
> +	int rc;
> +
> +	/* Account for all the DOE vectors needed */
> +	pci_doe_for_each_off(pdev, off) {
> +		int irq = pci_doe_get_irq_num(pdev, off);
> +
> +		if (irq < 0)
> +			continue;
> +		max_irqs = max(max_irqs, irq + 1);

This seems to assume that different DOEs will get independent vectors.
The driver needs to be prepared for DOE instances, Event notifications,
and mailbox commands to share a single MSI vector in the worst case.
Lets focus on polled mode DOE, or explicitly only support interrupt
based operation when no vector sharing is detected.

> +	}
> +
> +	if (!max_irqs)
> +		return;
> +
> +	cxlds->doe_use_irq = false;
> +
> +	/*
> +	 * Allocate enough vectors for the DOE's
> +	 */
> +	rc = pci_alloc_irq_vectors(pdev, max_irqs, max_irqs, PCI_IRQ_MSI |
> +							     PCI_IRQ_MSIX);
> +	if (rc != max_irqs) {
> +		pci_err(pdev, "Not enough interrupts; use polling\n");
> +		/* Some got allocated; clean them up */
> +		if (rc > 0)
> +			cxl_pci_free_irq_vectors(pdev);
> +		return;
> +	}
> +
> +	rc = devm_add_action_or_reset(dev, cxl_pci_free_irq_vectors, pdev);
> +	if (rc)
> +		return;
> +
> +	cxlds->doe_use_irq = true;
> +}
> +
> +/**
> + * devm_cxl_pci_create_doe - Scan and set up DOE mailboxes
> + *
> + * @cxlds: The CXL device state
> + */
> +static void devm_cxl_pci_create_doe(struct cxl_dev_state *cxlds)
> +{
> +	struct device *dev = cxlds->dev;
> +	struct pci_dev *pdev = to_pci_dev(dev);
> +	u16 off = 0;
> +	int num_mbs = 0;
> +	int rc;
> +
> +	pci_doe_for_each_off(pdev, off)
> +		num_mbs++;
> +
> +	if (!num_mbs) {
> +		pci_dbg(pdev, "0 DOE mailbox's found\n");
> +		return;
> +	}
> +
> +	cxlds->doe_mbs = devm_kcalloc(dev, num_mbs, sizeof(*cxlds->doe_mbs),
> +				      GFP_KERNEL);
> +	if (!cxlds->doe_mbs)
> +		return;
> +
> +	pci_doe_for_each_off(pdev, off) {
> +		struct pci_doe_mb *doe_mb;
> +		int irq = -1;
> +
> +		if (cxlds->doe_use_irq)
> +			irq = pci_doe_get_irq_num(pdev, off);
> +
> +		doe_mb = pci_doe_create_mb(pdev, off, irq);
> +		if (IS_ERR(doe_mb)) {
> +			pci_err(pdev,
> +				"Failed to create MB object for MB @ %x\n",
> +				off);
> +			doe_mb = NULL;
> +		}
> +
> +		cxlds->doe_mbs[cxlds->num_mbs] = doe_mb;
> +		cxlds->num_mbs++;
> +	}
> +
> +	rc = devm_add_action_or_reset(dev, cxl_doe_destroy_mb, cxlds);
> +	if (rc)
> +		return;
> +
> +	pci_info(pdev, "Configured %d DOE mailbox's\n", cxlds->num_mbs);
> +}
> +
>  static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  {
>  	struct cxl_register_map map;
> @@ -434,6 +545,9 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  
>  	cxlds->component_reg_phys = cxl_regmap_to_base(pdev, &map);
>  
> +	cxl_alloc_irq_vectors(cxlds);
> +	devm_cxl_pci_create_doe(cxlds);
> +
>  	rc = cxl_pci_setup_mailbox(cxlds);
>  	if (rc)
>  		return rc;
> -- 
> 2.35.1
> 

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