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SubjectRe: [PATCH 02/14] cxl/mem: Map memory device registers
On Fri, 29 Jan 2021, Ben Widawsky wrote:

> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> new file mode 100644
> index 000000000000..d81d0ba4617c
> --- /dev/null
> +++ b/drivers/cxl/cxl.h
> @@ -0,0 +1,17 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/* Copyright(c) 2020 Intel Corporation. */
> +
> +#ifndef __CXL_H__
> +#define __CXL_H__
> +
> +/**
> + * struct cxl_mem - A CXL memory device
> + * @pdev: The PCI device associated with this CXL device.
> + * @regs: IO mappings to the device's MMIO
> + */
> +struct cxl_mem {
> + struct pci_dev *pdev;
> + void __iomem *regs;
> +};
> +
> +#endif

Stupid question: can there be more than one CXL.mem capable logical
device? I only ask to determine if an ordinal is needed to enumerate
multiple LDs.

> diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
> index f4ee9a507ac9..a869c8dc24cc 100644
> --- a/drivers/cxl/mem.c
> +++ b/drivers/cxl/mem.c
> @@ -4,6 +4,58 @@
> #include <linux/pci.h>
> #include <linux/io.h>
> #include "pci.h"
> +#include "cxl.h"
> +
> +/**
> + * cxl_mem_create() - Create a new &struct cxl_mem.
> + * @pdev: The pci device associated with the new &struct cxl_mem.
> + * @reg_lo: Lower 32b of the register locator
> + * @reg_hi: Upper 32b of the register locator.
> + *
> + * Return: The new &struct cxl_mem on success, NULL on failure.
> + *
> + * Map the BAR for a CXL memory device. This BAR has the memory device's
> + * registers for the device as specified in CXL specification.
> + */
> +static struct cxl_mem *cxl_mem_create(struct pci_dev *pdev, u32 reg_lo,
> + u32 reg_hi)
> +{
> + struct device *dev = &pdev->dev;
> + struct cxl_mem *cxlm;
> + void __iomem *regs;
> + u64 offset;
> + u8 bar;
> + int rc;
> +
> + offset = ((u64)reg_hi << 32) | (reg_lo & CXL_REGLOC_ADDR_MASK);
> + bar = (reg_lo >> CXL_REGLOC_BIR_SHIFT) & CXL_REGLOC_BIR_MASK;
> +
> + /* Basic sanity check that BAR is big enough */
> + if (pci_resource_len(pdev, bar) < offset) {
> + dev_err(dev, "BAR%d: %pr: too small (offset: %#llx)\n", bar,
> + &pdev->resource[bar], (unsigned long long)offset);
> + return NULL;
> + }
> +
> + rc = pcim_iomap_regions(pdev, BIT(bar), pci_name(pdev));
> + if (rc != 0) {
> + dev_err(dev, "failed to map registers\n");
> + return NULL;
> + }
> +
> + cxlm = devm_kzalloc(&pdev->dev, sizeof(*cxlm), GFP_KERNEL);
> + if (!cxlm) {
> + dev_err(dev, "No memory available\n");
> + return NULL;
> + }
> +
> + regs = pcim_iomap_table(pdev)[bar];
> + cxlm->pdev = pdev;
> + cxlm->regs = regs + offset;
> +
> + dev_dbg(dev, "Mapped CXL Memory Device resource\n");
> + return cxlm;
> +}
>
> static int cxl_mem_dvsec(struct pci_dev *pdev, int dvsec)
> {
> @@ -32,15 +84,42 @@ static int cxl_mem_dvsec(struct pci_dev *pdev, int dvsec)
> static int cxl_mem_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> {
> struct device *dev = &pdev->dev;
> - int regloc;
> + struct cxl_mem *cxlm;
> + int rc, regloc, i;
> +
> + rc = pcim_enable_device(pdev);
> + if (rc)
> + return rc;
>
> regloc = cxl_mem_dvsec(pdev, PCI_DVSEC_ID_CXL_REGLOC);
> if (!regloc) {
> dev_err(dev, "register location dvsec not found\n");
> return -ENXIO;
> }
> + regloc += 0xc; /* Skip DVSEC + reserved fields */

Assuming the DVSEC revision number is always 0x0 or there's no value in
storing this in struct cxl_mem for the future.

Acked-by: David Rientjes <rientjes@google.com>

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