linux-kernel - Re: [PATCH 11/15] cxl/acpi: Extract the host's component register base address from RCRB

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Message-ID: <9E6742FC-BC9F-40E4-8812-7E34BC5C08CC@fb.com>
Date:   Thu, 8 Sep 2022 20:59:36 +0000
From:   "Jonathan Zhang (Infra)" <jonzhang@...com>
To:     Robert Richter <rrichter@....com>
CC:     Alison Schofield <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Ben Widawsky <bwidawsk@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        "linux-cxl@...r.kernel.org" <linux-cxl@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Terry Bowman <terry.bowman@....com>,
        Prakash Chauhan <hpc@...com>, Chris Petersen <cpetersen@...com>
Subject: Re: [PATCH 11/15] cxl/acpi: Extract the host's component register
 base address from RCRB



> On Aug 31, 2022, at 1:15 AM, Robert Richter <rrichter@....com> wrote:
> 
> A downstream port must be connected to a component register block.
> Determine its base address from the RCRB.
> 
> The implementation is analog to how cxl_setup_regs() is implemented
> for CXL VH mode. A struct cxl_component_reg_map is filled in, mapped
> and probed.
> 
> Signed-off-by: Terry Bowman <terry.bowman@....com>
> Signed-off-by: Robert Richter <rrichter@....com>
> ---
> drivers/cxl/acpi.c | 80 ++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 80 insertions(+)
> 
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> index 439df9df2741..88bbd2bb61fc 100644
> --- a/drivers/cxl/acpi.c
> +++ b/drivers/cxl/acpi.c
> @@ -401,12 +401,84 @@ static resource_size_t cxl_get_rcrb(u32 uid)
> 	return ctx.chbcr;
> }
> 
> +static resource_size_t cxl_get_component_reg_phys(resource_size_t rcrb)
> +{
> +	resource_size_t component_reg_phys;
> +	u32 bar0, bar1;
> +	void *addr;
> +
> +	/*
> +	 * RCRB's BAR[0..1] point to component block containing CXL subsystem
> +	 * component registers.
> +	 * CXL 8.2.4 - Component Register Layout Definition.
> +	 *
> +	 * Also, RCRB accesses must use MMIO readl()/readq() to guarantee
> +	 * 32/64-bit access.
> +	 * CXL 8.2.2 - CXL 1.1 Upstream and Downstream Port Subsystem Component
> +	 * Registers
> +	 */
> +	addr = ioremap(rcrb, PCI_BASE_ADDRESS_0 + SZ_8);
> +	bar0 = readl(addr + PCI_BASE_ADDRESS_0);
> +	bar1 = readl(addr + PCI_BASE_ADDRESS_1);
> +	iounmap(addr);
> +
> +	/* sanity check */
> +	if (bar0 & (PCI_BASE_ADDRESS_MEM_TYPE_1M | PCI_BASE_ADDRESS_SPACE_IO))
> +		return CXL_RESOURCE_NONE;
> +
> +	component_reg_phys = bar0 & PCI_BASE_ADDRESS_MEM_MASK;
> +	if (bar0 & PCI_BASE_ADDRESS_MEM_TYPE_64)
> +		component_reg_phys |= ((u64)bar1) << 32;
> +
> +	if (!component_reg_phys)
> +		return CXL_RESOURCE_NONE;
> +
> +	/*
> +	 * Must be 8k aligned (size of combined CXL 1.1 Downstream and
> +	 * Upstream Port RCRBs).
> +	 */
> +	if (component_reg_phys & (SZ_8K - 1))
> +		return CXL_RESOURCE_NONE;
> +
> +	return component_reg_phys;
> +}
> +
> +static int cxl_setup_component_reg(struct device *parent,
> +				   resource_size_t component_reg_phys)
> +{
> +	struct cxl_component_reg_map comp_map;
> +	void __iomem *base;
> +
> +	if (component_reg_phys == CXL_RESOURCE_NONE)
> +		return -EINVAL;
> +
> +	base = ioremap(component_reg_phys, SZ_64K);
> +	if (!base) {
> +		dev_err(parent, "failed to map registers\n");
> +		return -ENOMEM;
> +	}
> +
> +	cxl_probe_component_regs(parent, base, &comp_map);
> +	iounmap(base);
> +
> +	if (!comp_map.hdm_decoder.valid) {
> +		dev_err(parent, "HDM decoder registers not found\n");
> +		return -ENXIO;
> +	}
> +
> +	dev_dbg(parent, "Set up component registers\n");
> +
> +	return 0;
> +}
> +
> static int __init cxl_restricted_host_probe(struct platform_device *pdev)
> {
> 	struct pci_host_bridge *host = NULL;
> 	struct acpi_device *adev;
> 	unsigned long long uid = ~0;
> 	resource_size_t rcrb;
> +	resource_size_t component_reg_phys;
> +	int rc;
> 
> 	while ((host = cxl_find_next_rch(host)) != NULL) {
> 		adev = ACPI_COMPANION(&host->dev);
> @@ -425,10 +497,18 @@ static int __init cxl_restricted_host_probe(struct platform_device *pdev)
> 
> 		dev_dbg(&host->dev, "RCRB found: 0x%08llx\n", (u64)rcrb);
> 
> +		component_reg_phys = cxl_get_component_reg_phys(rcrb);
> +		rc = cxl_setup_component_reg(&host->dev, component_reg_phys);

cxl_setup_component_reg() calls cxl_probe_component_regs() which depends on the existence
of HDM decoder capability register. Such register does not exist when the device is in RCRB
mode, attached to a RCH.

> +		if (rc)
> +			goto fail;
> +
> 		dev_info(&host->dev, "host supports CXL\n");
> 	}
> 
> 	return 0;
> +fail:
> +	dev_err(&host->dev, "failed to initialize CXL host: %d\n", rc);
> +	return rc;
> }
> 
> static struct lock_class_key cxl_root_key;
> -- 
> 2.30.2
> 
>