Re: [PATCH 18/23] cxl/pci: Implement wait for media active

[Ben Widawsky <ben.widawsky@intel.com>]

On 21-11-23 11:09:34, Jonathan Cameron wrote:
> On Mon, 22 Nov 2021 14:57:51 -0800
> Ben Widawsky <ben.widawsky@intel.com> wrote:
> 
> > On 21-11-22 17:03:35, Jonathan Cameron wrote:
> > > On Fri, 19 Nov 2021 16:02:45 -0800
> > > Ben Widawsky <ben.widawsky@intel.com> wrote:
> > >   
> > > > CXL 2.0 8.1.3.8.2 defines "Memory_Active: When set, indicates that the
> > > > CXL Range 1 memory is fully initialized and available for software use.
> > > > Must be set within Range 1. Memory_Active_Timeout of deassertion of  
> > > 
> > > Range 1?
> > >   
> > 
> > Not my numbering... It's the first DVSEC range.
> 
> Ah, got it. Maybe Range 1: Memory Active timeout ?

I can, but this is just quoted from the spec. Would this be better:

The CXL Type 3 Memory Device Software Guide (Revision 1.0) describes the
need to check media active before using HDM. CXL 2.0 8.1.3.8.2 states:

  Memory_Active: When set, indicates that the CXL Range 1 memory is
  fully initialized and available for software use. Must be set within
  Range 1. Memory_Active_Timeout of deassertion of reset to CXL device
  if CXL.mem HwInit Mode=1

Unfortunately, Memory_Active can take quite a long time depending on
media size (up to 256s per 2.0 spec). Since the cxl_pci driver doesn't
care about this, a callback is exported as part of driver state for use
by drivers that do care.

> 
> > 
> > > > reset to CXL device if CXL.mem HwInit Mode=1" The CXL* Type 3 Memory
> > > > Device Software Guide (Revision 1.0) further describes the need to check
> > > > this bit before using HDM.
> > > > 
> > > > Unfortunately, Memory_Active can take quite a long time depending on
> > > > media size (up to 256s per 2.0 spec). Since the cxl_pci driver doesn't
> > > > care about this, a callback is exported as part of driver state for use
> > > > by drivers that do care.
> > > > 
> > > > Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>  
> > > 
> > > Same thing about size not being used...
> > >   
> > 
> > Yep, got it.
> > 
> > > > ---
> > > > This patch did not exist in RFCv2
> > > > ---
> > > >  drivers/cxl/cxlmem.h |  1 +
> > > >  drivers/cxl/pci.c    | 56 ++++++++++++++++++++++++++++++++++++++++++++
> > > >  2 files changed, 57 insertions(+)
> > > > 
> > > > diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
> > > > index eac5528ccaae..a9424dd4e5c3 100644
> > > > --- a/drivers/cxl/cxlmem.h
> > > > +++ b/drivers/cxl/cxlmem.h
> > > > @@ -167,6 +167,7 @@ struct cxl_dev_state {
> > > >  	struct cxl_endpoint_dvsec_info *info;
> > > >  
> > > >  	int (*mbox_send)(struct cxl_dev_state *cxlds, struct cxl_mbox_cmd *cmd);
> > > > +	int (*wait_media_ready)(struct cxl_dev_state *cxlds);
> > > >  };
> > > >  
> > > >  enum cxl_opcode {
> > > > diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> > > > index b3f46045bf3e..f1a68bfe5f77 100644
> > > > --- a/drivers/cxl/pci.c
> > > > +++ b/drivers/cxl/pci.c
> > > > @@ -496,6 +496,60 @@ static int wait_for_valid(struct cxl_dev_state *cxlds)
> > > >  	return valid ? 0 : -ETIMEDOUT;
> > > >  }
> > > >  
> > > > +/*
> > > > + * Implements Figure 43 of the CXL Type 3 Memory Device Software Guide. Waits a
> > > > + * full 256s no matter what the device reports.
> > > > + */
> > > > +static int wait_for_media_ready(struct cxl_dev_state *cxlds)
> > > > +{
> > > > +	const unsigned long timeout = jiffies + (256 * HZ);
> > > > +	struct pci_dev *pdev = to_pci_dev(cxlds->dev);
> > > > +	u64 md_status;
> > > > +	bool active;
> > > > +	int rc;
> > > > +
> > > > +	rc = wait_for_valid(cxlds);
> > > > +	if (rc)
> > > > +		return rc;
> > > > +
> > > > +	do {
> > > > +		u64 size;
> > > > +		u32 temp;
> > > > +		int rc;
> > > > +
> > > > +		rc = pci_read_config_dword(pdev, CDPDR(cxlds, 0, SIZE, HIGH),
> > > > +					   &temp);
> > > > +		if (rc)
> > > > +			return -ENXIO;
> > > > +		size = (u64)temp << 32;
> > > > +
> > > > +		rc = pci_read_config_dword(pdev, CDPDR(cxlds, 0, SIZE, LOW),
> > > > +					   &temp);
> > > > +		if (rc)
> > > > +			return -ENXIO;
> > > > +		size |= temp & CXL_DVSEC_PCIE_DEVICE_MEM_SIZE_LOW_MASK;
> > > > +
> > > > +		active = FIELD_GET(CXL_DVSEC_PCIE_DEVICE_MEM_ACTIVE, temp);  
> > > 
> > > Only need to read the register to get active for this particular functionality.
> > >   
> > > > +		if (active)
> > > > +			break;
> > > > +		cpu_relax();
> > > > +		mdelay(100);
> > > > +	} while (!time_after(jiffies, timeout));
> > > > +
> > > > +	if (!active)
> > > > +		return -ETIMEDOUT;
> > > > +
> > > > +	rc = check_device_status(cxlds);
> > > > +	if (rc)
> > > > +		return rc;
> > > > +
> > > > +	md_status = readq(cxlds->regs.memdev + CXLMDEV_STATUS_OFFSET);
> > > > +	if (!CXLMDEV_READY(md_status))
> > > > +		return -EIO;
> > > > +
> > > > +	return 0;
> > > > +}
> > > > +
> > > >  static struct cxl_endpoint_dvsec_info *dvsec_ranges(struct cxl_dev_state *cxlds)
> > > >  {
> > > >  	struct pci_dev *pdev = to_pci_dev(cxlds->dev);
> > > > @@ -598,6 +652,8 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> > > >  	if (!cxlds->device_dvsec)
> > > >  		dev_warn(&pdev->dev,
> > > >  			 "Device DVSEC not present. Expect limited functionality.\n");
> > > > +	else
> > > > +		cxlds->wait_media_ready = wait_for_media_ready;
> > > >  
> > > >  	rc = cxl_setup_regs(pdev, CXL_REGLOC_RBI_MEMDEV, &map);
> > > >  	if (rc)  
> > >   
>