On Tue, 9 Feb 2021 16:02:53 -0800 Ben Widawsky <ben.widawsky@xxxxxxxxx> wrote: > 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. > > Link: https://www.computeexpresslink.org/download-the-specification > Signed-off-by: Ben Widawsky <ben.widawsky@xxxxxxxxx> > Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx> Hi Ben, > +/** > + * cxl_mem_mbox_send_cmd() - Send a mailbox command to a memory device. > + * @cxlm: The CXL memory device to communicate with. > + * @mbox_cmd: Command to send to the memory device. > + * > + * Context: Any context. Expects mbox_lock to be held. > + * Return: -ETIMEDOUT if timeout occurred waiting for completion. 0 on success. > + * Caller should check the return code in @mbox_cmd to make sure it > + * succeeded. cxl_xfer_log() doesn't check mbox_cmd->return_code and for my test it currently enters an infinite loop as a result. I haven't checked other paths, but to my mind it is not a good idea to require two levels of error checking - the example here proves how easy it is to forget one. Now all I have to do is figure out why I'm getting an error in the first place! Jonathan > + * > + * This is a generic form of the CXL mailbox send command, thus the only I/O > + * operations used are cxl_read_mbox_reg(). Memory devices, and perhaps other > + * types of CXL devices may have further information available upon error > + * conditions. > + * > + * The CXL spec allows for up to two mailboxes. The intention is for the primary > + * mailbox to be OS controlled and the secondary mailbox to be used by system > + * firmware. This allows the OS and firmware to communicate with the device and > + * not need to coordinate with each other. The driver only uses the primary > + * mailbox. > + */ > +static int cxl_mem_mbox_send_cmd(struct cxl_mem *cxlm, > + struct mbox_cmd *mbox_cmd) > +{ > + void __iomem *payload = cxlm->mbox_regs + CXLDEV_MBOX_PAYLOAD_OFFSET; > + u64 cmd_reg, status_reg; > + size_t out_len; > + int rc; > + > + lockdep_assert_held(&cxlm->mbox_mutex); > + > + /* > + * Here are the steps from 8.2.8.4 of the CXL 2.0 spec. > + * 1. Caller reads MB Control Register to verify doorbell is clear > + * 2. Caller writes Command Register > + * 3. Caller writes Command Payload Registers if input payload is non-empty > + * 4. Caller writes MB Control Register to set doorbell > + * 5. Caller either polls for doorbell to be clear or waits for interrupt if configured > + * 6. Caller reads MB Status Register to fetch Return code > + * 7. If command successful, Caller reads Command Register to get Payload Length > + * 8. If output payload is non-empty, host reads Command Payload Registers > + * > + * Hardware is free to do whatever it wants before the doorbell is rung, > + * and isn't allowed to change anything after it clears the doorbell. As > + * such, steps 2 and 3 can happen in any order, and steps 6, 7, 8 can > + * also happen in any order (though some orders might not make sense). > + */ > + > + /* #1 */ > + if (cxl_doorbell_busy(cxlm)) { > + dev_err_ratelimited(&cxlm->pdev->dev, > + "Mailbox re-busy after acquiring\n"); > + return -EBUSY; > + } > + > + cmd_reg = FIELD_PREP(CXLDEV_MBOX_CMD_COMMAND_OPCODE_MASK, > + mbox_cmd->opcode); > + if (mbox_cmd->size_in) { > + if (WARN_ON(!mbox_cmd->payload_in)) > + return -EINVAL; > + > + cmd_reg |= FIELD_PREP(CXLDEV_MBOX_CMD_PAYLOAD_LENGTH_MASK, > + mbox_cmd->size_in); > + memcpy_toio(payload, mbox_cmd->payload_in, mbox_cmd->size_in); > + } > + > + /* #2, #3 */ > + writeq(cmd_reg, cxlm->mbox_regs + CXLDEV_MBOX_CMD_OFFSET); > + > + /* #4 */ > + dev_dbg(&cxlm->pdev->dev, "Sending command\n"); > + writel(CXLDEV_MBOX_CTRL_DOORBELL, > + cxlm->mbox_regs + CXLDEV_MBOX_CTRL_OFFSET); > + > + /* #5 */ > + rc = cxl_mem_wait_for_doorbell(cxlm); > + if (rc == -ETIMEDOUT) { > + cxl_mem_mbox_timeout(cxlm, mbox_cmd); > + return rc; > + } > + > + /* #6 */ > + status_reg = readq(cxlm->mbox_regs + CXLDEV_MBOX_STATUS_OFFSET); > + mbox_cmd->return_code = > + FIELD_GET(CXLDEV_MBOX_STATUS_RET_CODE_MASK, status_reg); > + > + if (mbox_cmd->return_code != 0) { > + dev_dbg(&cxlm->pdev->dev, "Mailbox operation had an error\n"); > + return 0; I'd return some sort of error in this path. Otherwise the sort of missing handling I mention above is too easy to hit. > + } > + > + /* #7 */ > + cmd_reg = readq(cxlm->mbox_regs + CXLDEV_MBOX_CMD_OFFSET); > + out_len = FIELD_GET(CXLDEV_MBOX_CMD_PAYLOAD_LENGTH_MASK, cmd_reg); > + > + /* #8 */ > + if (out_len && mbox_cmd->payload_out) > + memcpy_fromio(mbox_cmd->payload_out, payload, out_len); > + > + mbox_cmd->size_out = out_len; > + > + return 0; > +} > + > +/** > + * cxl_mem_mbox_get() - Acquire exclusive access to the mailbox. > + * @cxlm: The memory device to gain access to. > + * > + * Context: Any context. Takes the mbox_lock. > + * Return: 0 if exclusive access was acquired. > + */ > +static int cxl_mem_mbox_get(struct cxl_mem *cxlm) > +{ > + struct device *dev = &cxlm->pdev->dev; > + int rc = -EBUSY; > + u64 md_status; > + > + mutex_lock_io(&cxlm->mbox_mutex); > + > + /* > + * XXX: There is some amount of ambiguity in the 2.0 version of the spec > + * around the mailbox interface ready (8.2.8.5.1.1). The purpose of the > + * bit is to allow firmware running on the device to notify the driver > + * that it's ready to receive commands. It is unclear if the bit needs > + * to be read for each transaction mailbox, ie. the firmware can switch > + * it on and off as needed. Second, there is no defined timeout for > + * mailbox ready, like there is for the doorbell interface. > + * > + * Assumptions: > + * 1. The firmware might toggle the Mailbox Interface Ready bit, check > + * it for every command. > + * > + * 2. If the doorbell is clear, the firmware should have first set the > + * Mailbox Interface Ready bit. Therefore, waiting for the doorbell > + * to be ready is sufficient. > + */ > + rc = cxl_mem_wait_for_doorbell(cxlm); > + if (rc) { > + dev_warn(dev, "Mailbox interface not ready\n"); > + goto out; > + } > + > + md_status = readq(cxlm->memdev_regs + CXLMDEV_STATUS_OFFSET); > + if (!(md_status & CXLMDEV_MBOX_IF_READY && CXLMDEV_READY(md_status))) { > + dev_err(dev, > + "mbox: reported doorbell ready, but not mbox ready\n"); > + goto out; > + } > + > + /* > + * Hardware shouldn't allow a ready status but also have failure bits > + * set. Spit out an error, this should be a bug report > + */ > + rc = -EFAULT; > + if (md_status & CXLMDEV_DEV_FATAL) { > + dev_err(dev, "mbox: reported ready, but fatal\n"); > + goto out; > + } > + if (md_status & CXLMDEV_FW_HALT) { > + dev_err(dev, "mbox: reported ready, but halted\n"); > + goto out; > + } > + if (CXLMDEV_RESET_NEEDED(md_status)) { > + dev_err(dev, "mbox: reported ready, but reset needed\n"); > + goto out; > + } > + > + /* with lock held */ > + return 0; > + > +out: > + mutex_unlock(&cxlm->mbox_mutex); > + return rc; > +} > + > +/** > + * cxl_mem_mbox_put() - Release exclusive access to the mailbox. > + * @cxlm: The CXL memory device to communicate with. > + * > + * Context: Any context. Expects mbox_lock to be held. > + */ > +static void cxl_mem_mbox_put(struct cxl_mem *cxlm) > +{ > + mutex_unlock(&cxlm->mbox_mutex); > +} > + > +/** > + * cxl_mem_setup_regs() - Setup necessary MMIO. > + * @cxlm: The CXL memory device to communicate with. > + * > + * Return: 0 if all necessary registers mapped. > + * > + * A memory device is required by spec to implement a certain set of MMIO > + * regions. The purpose of this function is to enumerate and map those > + * registers. > + */ > +static int cxl_mem_setup_regs(struct cxl_mem *cxlm) > +{ > + struct device *dev = &cxlm->pdev->dev; > + int cap, cap_count; > + u64 cap_array; > + > + cap_array = readq(cxlm->regs + CXLDEV_CAP_ARRAY_OFFSET); > + if (FIELD_GET(CXLDEV_CAP_ARRAY_ID_MASK, cap_array) != > + CXLDEV_CAP_ARRAY_CAP_ID) > + return -ENODEV; > + > + cap_count = FIELD_GET(CXLDEV_CAP_ARRAY_COUNT_MASK, cap_array); > + > + for (cap = 1; cap <= cap_count; cap++) { > + void __iomem *register_block; > + u32 offset; > + u16 cap_id; > + > + cap_id = readl(cxlm->regs + cap * 0x10) & 0xffff; > + offset = readl(cxlm->regs + cap * 0x10 + 0x4); > + register_block = cxlm->regs + offset; > + > + switch (cap_id) { > + case CXLDEV_CAP_CAP_ID_DEVICE_STATUS: > + dev_dbg(dev, "found Status capability (0x%x)\n", offset); > + cxlm->status_regs = register_block; > + break; > + case CXLDEV_CAP_CAP_ID_PRIMARY_MAILBOX: > + dev_dbg(dev, "found Mailbox capability (0x%x)\n", offset); > + cxlm->mbox_regs = register_block; > + break; > + case CXLDEV_CAP_CAP_ID_SECONDARY_MAILBOX: > + dev_dbg(dev, "found Secondary Mailbox capability (0x%x)\n", offset); > + break; > + case CXLDEV_CAP_CAP_ID_MEMDEV: > + dev_dbg(dev, "found Memory Device capability (0x%x)\n", offset); > + cxlm->memdev_regs = register_block; > + break; > + default: > + dev_dbg(dev, "Unknown cap ID: %d (0x%x)\n", cap_id, offset); > + break; > + } > + } > + > + if (!cxlm->status_regs || !cxlm->mbox_regs || !cxlm->memdev_regs) { > + dev_err(dev, "registers not found: %s%s%s\n", > + !cxlm->status_regs ? "status " : "", > + !cxlm->mbox_regs ? "mbox " : "", > + !cxlm->memdev_regs ? "memdev" : ""); > + return -ENXIO; > + } > + > + return 0; > +} > + > +static int cxl_mem_setup_mailbox(struct cxl_mem *cxlm) > +{ > + const int cap = readl(cxlm->mbox_regs + CXLDEV_MBOX_CAPS_OFFSET); > + > + cxlm->payload_size = > + 1 << FIELD_GET(CXLDEV_MBOX_CAP_PAYLOAD_SIZE_MASK, cap); > + > + /* > + * CXL 2.0 8.2.8.4.3 Mailbox Capabilities Register > + * > + * If the size is too small, mandatory commands will not work and so > + * there's no point in going forward. If the size is too large, there's > + * no harm is soft limiting it. > + */ > + cxlm->payload_size = min_t(size_t, cxlm->payload_size, SZ_1M); > + if (cxlm->payload_size < 256) { > + dev_err(&cxlm->pdev->dev, "Mailbox is too small (%zub)", > + cxlm->payload_size); > + return -ENXIO; > + } > + > + dev_dbg(&cxlm->pdev->dev, "Mailbox payload sized %zu", > + cxlm->payload_size); > + > + return 0; > +} > + > +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; > + > + cxlm = devm_kzalloc(&pdev->dev, sizeof(*cxlm), GFP_KERNEL); > + if (!cxlm) { > + dev_err(dev, "No memory available\n"); > + return NULL; > + } > + > + offset = ((u64)reg_hi << 32) | FIELD_GET(CXL_REGLOC_ADDR_MASK, reg_lo); > + bar = FIELD_GET(CXL_REGLOC_BIR_MASK, reg_lo); > + > + /* 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; > + } > + regs = pcim_iomap_table(pdev)[bar]; > + > + mutex_init(&cxlm->mbox_mutex); > + 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) > { > @@ -28,10 +423,85 @@ static int cxl_mem_dvsec(struct pci_dev *pdev, int dvsec) > return 0; > } > > +/** > + * cxl_mem_identify() - Send the IDENTIFY command to the device. > + * @cxlm: The device to identify. > + * > + * Return: 0 if identify was executed successfully. > + * > + * This will dispatch the identify command to the device and on success populate > + * structures to be exported to sysfs. > + */ > +static int cxl_mem_identify(struct cxl_mem *cxlm) > +{ > + struct cxl_mbox_identify { > + char fw_revision[0x10]; > + __le64 total_capacity; > + __le64 volatile_capacity; > + __le64 persistent_capacity; > + __le64 partition_align; > + __le16 info_event_log_size; > + __le16 warning_event_log_size; > + __le16 failure_event_log_size; > + __le16 fatal_event_log_size; > + __le32 lsa_size; > + u8 poison_list_max_mer[3]; > + __le16 inject_poison_limit; > + u8 poison_caps; > + u8 qos_telemetry_caps; > + } __packed id; > + struct mbox_cmd mbox_cmd = { > + .opcode = CXL_MBOX_OP_IDENTIFY, > + .payload_out = &id, > + .size_in = 0, > + }; > + int rc; > + > + /* Retrieve initial device memory map */ > + rc = cxl_mem_mbox_get(cxlm); > + if (rc) > + return rc; > + > + rc = cxl_mem_mbox_send_cmd(cxlm, &mbox_cmd); > + cxl_mem_mbox_put(cxlm); > + if (rc) > + return rc; > + > + /* TODO: Handle retry or reset responses from firmware. */ > + if (mbox_cmd.return_code != CXL_MBOX_SUCCESS) { > + dev_err(&cxlm->pdev->dev, "Mailbox command failed (%d)\n", > + mbox_cmd.return_code); > + return -ENXIO; > + } > + > + if (mbox_cmd.size_out != sizeof(id)) > + return -ENXIO; > + > + /* > + * TODO: enumerate DPA map, as 'ram' and 'pmem' do not alias. > + * For now, only the capacity is exported in sysfs > + */ > + cxlm->ram.range.start = 0; > + cxlm->ram.range.end = le64_to_cpu(id.volatile_capacity) - 1; > + > + cxlm->pmem.range.start = 0; > + cxlm->pmem.range.end = le64_to_cpu(id.persistent_capacity) - 1; > + > + memcpy(cxlm->firmware_version, id.fw_revision, sizeof(id.fw_revision)); > + > + return rc; > +} > + > 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; > + u32 regloc_size; > + > + rc = pcim_enable_device(pdev); > + if (rc) > + return rc; > > regloc = cxl_mem_dvsec(pdev, PCI_DVSEC_ID_CXL_REGLOC_OFFSET); > if (!regloc) { > @@ -39,7 +509,44 @@ static int cxl_mem_probe(struct pci_dev *pdev, const struct pci_device_id *id) > return -ENXIO; > } > > - return 0; > + /* Get the size of the Register Locator DVSEC */ > + pci_read_config_dword(pdev, regloc + PCI_DVSEC_HEADER1, ®loc_size); > + regloc_size = FIELD_GET(PCI_DVSEC_HEADER1_LENGTH_MASK, regloc_size); > + > + regloc += PCI_DVSEC_ID_CXL_REGLOC_BLOCK1_OFFSET; > + > + rc = -ENXIO; > + for (i = regloc; i < regloc + regloc_size; i += 8) { > + u32 reg_lo, reg_hi; > + u8 reg_type; > + > + /* "register low and high" contain other bits */ > + pci_read_config_dword(pdev, i, ®_lo); > + pci_read_config_dword(pdev, i + 4, ®_hi); > + > + reg_type = FIELD_GET(CXL_REGLOC_RBI_MASK, reg_lo); > + > + if (reg_type == CXL_REGLOC_RBI_MEMDEV) { > + rc = 0; > + cxlm = cxl_mem_create(pdev, reg_lo, reg_hi); > + if (!cxlm) > + rc = -ENODEV; > + break; > + } > + } > + > + if (rc) > + return rc; > + > + rc = cxl_mem_setup_regs(cxlm); > + if (rc) > + return rc; > + > + rc = cxl_mem_setup_mailbox(cxlm); > + if (rc) > + return rc; > + > + return cxl_mem_identify(cxlm); > } > > static const struct pci_device_id cxl_mem_pci_tbl[] = { > diff --git a/drivers/cxl/pci.h b/drivers/cxl/pci.h > index f135b9f7bb21..ffcbc13d7b5b 100644 > --- a/drivers/cxl/pci.h > +++ b/drivers/cxl/pci.h > @@ -14,5 +14,18 @@ > #define PCI_DVSEC_ID_CXL 0x0 > > #define PCI_DVSEC_ID_CXL_REGLOC_OFFSET 0x8 > +#define PCI_DVSEC_ID_CXL_REGLOC_BLOCK1_OFFSET 0xC > + > +/* BAR Indicator Register (BIR) */ > +#define CXL_REGLOC_BIR_MASK GENMASK(2, 0) > + > +/* Register Block Identifier (RBI) */ > +#define CXL_REGLOC_RBI_MASK GENMASK(15, 8) > +#define CXL_REGLOC_RBI_EMPTY 0 > +#define CXL_REGLOC_RBI_COMPONENT 1 > +#define CXL_REGLOC_RBI_VIRT 2 > +#define CXL_REGLOC_RBI_MEMDEV 3 > + > +#define CXL_REGLOC_ADDR_MASK GENMASK(31, 16) > > #endif /* __CXL_PCI_H__ */ > diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h > index e709ae8235e7..6267ca9ae683 100644 > --- a/include/uapi/linux/pci_regs.h > +++ b/include/uapi/linux/pci_regs.h > @@ -1080,6 +1080,7 @@ > > /* Designated Vendor-Specific (DVSEC, PCI_EXT_CAP_ID_DVSEC) */ > #define PCI_DVSEC_HEADER1 0x4 /* Designated Vendor-Specific Header1 */ > +#define PCI_DVSEC_HEADER1_LENGTH_MASK 0xFFF00000 > #define PCI_DVSEC_HEADER2 0x8 /* Designated Vendor-Specific Header2 */ > > /* Data Link Feature */
