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Provide enough functionality to utilize the mailbox of a memory device. The mailbox is used to interact with the firmware running on the memory device. The flow is proven with one implemented command, "identify". Because the class code has already told the driver this is a memory device and the identify command is mandatory. CXL devices contain an array of capabilities that describe the interactions software can have with the device or firmware running on the device. A CXL compliant device must implement the device status and the mailbox capability. Additionally, a CXL compliant memory device must implement the memory device capability. Each of the capabilities can [will] provide an offset within the MMIO region for interacting with the CXL device. The capabilities tell the driver how to find and map the register space for CXL Memory Devices. The registers are required to utilize the CXL spec defined mailbox interface. The spec outlines two mailboxes, primary and secondary. The secondary mailbox is earmarked for system firmware, and not handled in this driver. Primary mailboxes are capable of generating an interrupt when submitting a background command. That implementation is saved for a later time. Reported-by: Colin Ian King <colin.king@canonical.com> (coverity) Reported-by: Dan Carpenter <dan.carpenter@oracle.com> (smatch) Signed-off-by: Ben Widawsky <ben.widawsky@intel.com> Reviewed-by: Dan Williams <dan.j.williams@intel.com> (v2) Link: https://www.computeexpresslink.org/download-the-specification Link: https://lore.kernel.org/r/20210217040958.1354670-3-ben.widawsky@intel.com Signed-off-by: Dan Williams <dan.j.williams@intel.com>
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962 B
ReStructuredText
30 lines
962 B
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.. SPDX-License-Identifier: GPL-2.0
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.. include:: <isonum.txt>
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===================================
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Compute Express Link Memory Devices
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===================================
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A Compute Express Link Memory Device is a CXL component that implements the
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CXL.mem protocol. It contains some amount of volatile memory, persistent memory,
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or both. It is enumerated as a PCI device for configuration and passing
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messages over an MMIO mailbox. Its contribution to the System Physical
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Address space is handled via HDM (Host Managed Device Memory) decoders
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that optionally define a device's contribution to an interleaved address
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range across multiple devices underneath a host-bridge or interleaved
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across host-bridges.
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Driver Infrastructure
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=====================
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This section covers the driver infrastructure for a CXL memory device.
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CXL Memory Device
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-----------------
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.. kernel-doc:: drivers/cxl/mem.c
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:doc: cxl mem
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.. kernel-doc:: drivers/cxl/mem.c
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:internal:
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