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Date: Thu, 22 Jun 2023 16:58:08 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: Terry Bowman <terry.bowman@....com>, <alison.schofield@...el.com>,
<vishal.l.verma@...el.com>, <ira.weiny@...el.com>,
<bwidawsk@...nel.org>, <dan.j.williams@...el.com>,
<Jonathan.Cameron@...wei.com>, <linux-cxl@...r.kernel.org>
CC: <rrichter@....com>, <linux-kernel@...r.kernel.org>,
<bhelgaas@...gle.com>
Subject: Re: [PATCH v6 14/27] cxl/pci: Early setup RCH dport component
registers from RCRB
On 6/21/23 20:51, Terry Bowman wrote:
> From: Robert Richter <rrichter@....com>
>
> CXL RAS capabilities must be enabled and accessible as soon as the CXL
> endpoint is detected in the PCI hierarchy and bound to the cxl_pci
> driver. This needs to be independent of other modules such as cxl_port
> or cxl_mem.
>
> CXL RAS capabilities reside in the Component Registers. For an RCH
> this is determined by probing RCRB which is implemented very late once
> the CXL Memory Device is created.
>
> Change this by moving the RCRB probe to the cxl_pci driver. Do this by
> using a new introduced function cxl_pci_find_port() similar to
> cxl_mem_find_port() to determine the involved dport by the endpoint's
> PCI handle. Plug this into the existing cxl_pci_setup_regs() function
> to setup Component Registers. Probe the RCRB in case the Component
> Registers cannot be located through the CXL Register Locator
> capability.
>
> This unifies code and early sets up the Component Registers at the
> same time for both, VH and RCH mode. Only the cxl_pci driver is
> involved for this. This allows an early mapping of the CXL RAS
> capability registers.
>
> Signed-off-by: Robert Richter <rrichter@....com>
> Signed-off-by: Terry Bowman <terry.bowman@....com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Reviewed-by: Dave Jiang <dave.jiang@...el.com>
> ---
> drivers/cxl/core/port.c | 7 +++++
> drivers/cxl/cxl.h | 2 ++
> drivers/cxl/mem.c | 9 -------
> drivers/cxl/pci.c | 57 ++++++++++++++++++++++++++++++++++-------
> 4 files changed, 57 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index e0d2e7596440..679226023f0c 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -1480,6 +1480,13 @@ int devm_cxl_enumerate_ports(struct cxl_memdev *cxlmd)
> }
> EXPORT_SYMBOL_NS_GPL(devm_cxl_enumerate_ports, CXL);
>
> +struct cxl_port *cxl_pci_find_port(struct pci_dev *pdev,
> + struct cxl_dport **dport)
> +{
> + return find_cxl_port(pdev->dev.parent, dport);
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_pci_find_port, CXL);
> +
> struct cxl_port *cxl_mem_find_port(struct cxl_memdev *cxlmd,
> struct cxl_dport **dport)
> {
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 7fbc52b81554..fe95f08acb69 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -664,6 +664,8 @@ struct cxl_port *find_cxl_root(struct cxl_port *port);
> int devm_cxl_enumerate_ports(struct cxl_memdev *cxlmd);
> void cxl_bus_rescan(void);
> void cxl_bus_drain(void);
> +struct cxl_port *cxl_pci_find_port(struct pci_dev *pdev,
> + struct cxl_dport **dport);
> struct cxl_port *cxl_mem_find_port(struct cxl_memdev *cxlmd,
> struct cxl_dport **dport);
> bool schedule_cxl_memdev_detach(struct cxl_memdev *cxlmd);
> diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
> index 7638a7f8f333..205e2e280aed 100644
> --- a/drivers/cxl/mem.c
> +++ b/drivers/cxl/mem.c
> @@ -65,15 +65,6 @@ static int devm_cxl_add_endpoint(struct device *host, struct cxl_memdev *cxlmd,
> ep->next = down;
> }
>
> - /*
> - * The component registers for an RCD might come from the
> - * host-bridge RCRB if they are not already mapped via the
> - * typical register locator mechanism.
> - */
> - if (parent_dport->rch && cxlds->component_reg_phys == CXL_RESOURCE_NONE)
> - cxlds->component_reg_phys =
> - cxl_rcd_component_reg_phys(&cxlmd->dev, parent_dport);
> -
> endpoint = devm_cxl_add_port(host, &cxlmd->dev,
> cxlds->component_reg_phys,
> parent_dport);
> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> index 945ca0304d68..99a75c54ee39 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/pci.c
> @@ -274,27 +274,66 @@ static int cxl_pci_setup_mailbox(struct cxl_dev_state *cxlds)
> return 0;
> }
>
> +/*
> + * Assume that any RCIEP that emits the CXL memory expander class code
> + * is an RCD
> + */
> +static bool is_cxl_restricted(struct pci_dev *pdev)
> +{
> + return pci_pcie_type(pdev) == PCI_EXP_TYPE_RC_END;
> +}
> +
> +static int cxl_rcrb_get_comp_regs(struct pci_dev *pdev,
> + struct cxl_register_map *map)
> +{
> + struct cxl_port *port;
> + struct cxl_dport *dport;
> + resource_size_t component_reg_phys;
> +
> + *map = (struct cxl_register_map) {
> + .dev = &pdev->dev,
> + .resource = CXL_RESOURCE_NONE,
> + };
> +
> + port = cxl_pci_find_port(pdev, &dport);
> + if (!port)
> + return -EPROBE_DEFER;
> +
> + component_reg_phys = cxl_rcd_component_reg_phys(&pdev->dev, dport);
> +
> + put_device(&port->dev);
> +
> + if (component_reg_phys == CXL_RESOURCE_NONE)
> + return -ENXIO;
> +
> + map->resource = component_reg_phys;
> + map->reg_type = CXL_REGLOC_RBI_COMPONENT;
> + map->max_size = CXL_COMPONENT_REG_BLOCK_SIZE;
> +
> + return 0;
> +}
> +
> static int cxl_pci_setup_regs(struct pci_dev *pdev, enum cxl_regloc_type type,
> struct cxl_register_map *map)
> {
> int rc;
>
> rc = cxl_find_regblock(pdev, type, map);
> +
> + /*
> + * If the Register Locator DVSEC does not exist, check if it
> + * is an RCH and try to extract the Component Registers from
> + * an RCRB.
> + */
> + if (rc && type == CXL_REGLOC_RBI_COMPONENT && is_cxl_restricted(pdev))
> + rc = cxl_rcrb_get_comp_regs(pdev, map);
> +
> if (rc)
> return rc;
>
> return cxl_setup_regs(map);
> }
>
> -/*
> - * Assume that any RCIEP that emits the CXL memory expander class code
> - * is an RCD
> - */
> -static bool is_cxl_restricted(struct pci_dev *pdev)
> -{
> - return pci_pcie_type(pdev) == PCI_EXP_TYPE_RC_END;
> -}
> -
> /*
> * CXL v3.0 6.2.3 Table 6-4
> * The table indicates that if PCIe Flit Mode is set, then CXL is in 256B flits
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