On Wed, 10 Feb 2021 08:55:57 -0800
Ben Widawsky <ben.widaw...@intel.com> wrote:

> On 21-02-10 15:07:59, Jonathan Cameron wrote:
> > On Wed, 10 Feb 2021 13:32:52 +0000
> > Jonathan Cameron <jonathan.came...@huawei.com> wrote:
> >   
> > > On Tue, 9 Feb 2021 16:02:53 -0800
> > > Ben Widawsky <ben.widaw...@intel.com> 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.widaw...@intel.com>
> > > > Reviewed-by: Dan Williams <dan.j.willi...@intel.com>    
> > > 
> > > 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 meant to fix that.
> 
> > > 
> > > 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.  
> 
> Demonstrably, you're correct. I think it would be good to have a kernel only
> mbox command that does the error checking though. Let me type something up and
> see how it looks.
> 
> > > 
> > > Now all I have to do is figure out why I'm getting an error in the first 
> > > place!  
> > 
> > For reference this seems to be our old issue of arm64 memcpy_fromio() only 
> > doing 8 byte
> > or 1 byte copies.  The hack in QEMU to allow that to work, doesn't work.
> > Result is that 1 byte reads replicate across the register
> > (in this case instead of 0000001c I get 1c1c1c1c)
> > 
> > For these particular registers, we are covered by the rules in 8.2 which 
> > says that
> > a 1, 2, 4, 8 aligned reads of 64 bit registers etc are fine.
> > 
> > So we should not have to care.  This isn't true for the component registers 
> > where
> > we need to guarantee 4 or 8 byte reads only.
> > 
> > For this particular issue the mailbox_read_reg() function in the QEMU code
> > needs to handle the size 1 case and set min_access_size = 1 for
> > mailbox_ops.  Logically it should also handle the 2 byte case I think,
> > but I'm not hitting that.
> > 
> > Jonathan  
> 
> I think the latest QEMU patches should do the right thing (I have a v4 branch 
> if
> you want to try it). If it doesn't, it'd be worth debugging. The memory
> accessors should split up or combine the reads/writes to whatever the 
> emulation
> supports (4 or 8 only in this case).
> 
> We can move this discussion to the QEMU list if it's not just a simple bug on 
> my
> part.

I'm on your v4 QEMU branch.

I can follow up in the QEMU thread, but needs to do 1 byte reads as well.
(but as I'm here and someone might find this thread)

The arm64 implementation is 'interesting'.  Maybe we want to fix it but I
suspect we'll have a non trivial issue arguing it is broken.

CXL spec allows (I think) both 1 and 2 byte reads to this particular register.

/*
 * Copy data from IO memory space to "real" memory space.
 */
void __memcpy_fromio(void *to, const volatile void __iomem *from, size_t count)
{
        while (count && !IS_ALIGNED((unsigned long)from, 8)) {
                *(u8 *)to = __raw_readb(from);
                from++;
                to++;
                count--;
        }

        while (count >= 8) {
                *(u64 *)to = __raw_readq(from);
                from += 8;
                to += 8;
                count -= 8;
        }

        while (count) {
                *(u8 *)to = __raw_readb(from);
                from++;
                to++;
                count--;
        }
}
EXPORT_SYMBOL(__memcpy_fromio);

> 
> >   
> > > 
> > > 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, 
> > > > &regloc_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, &reg_lo);
> > > > +               pci_read_config_dword(pdev, i + 4, &reg_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 */    
> > >   
> >   

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