Re: [PATCH 13/13] cxl: Program decoders for regions

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

On 22-01-07 16:18:12, Jonathan Cameron wrote:
> On Thu,  6 Jan 2022 16:37:56 -0800
> Ben Widawsky <ben.widawsky@intel.com> wrote:
> 
> > Do the HDM decoder programming for all endpoints and host bridges in a
> > region. Switches are currently unimplemented.
> > 
> > Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
> > ---
> >  drivers/cxl/core/hdm.c | 198 +++++++++++++++++++++++++++++++++++++++++
> >  drivers/cxl/cxl.h      |   3 +
> >  drivers/cxl/region.c   |  39 +++++++-
> >  3 files changed, 237 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> > index 44e48cea8cd4..c7293cbd8547 100644
> > --- a/drivers/cxl/core/hdm.c
> > +++ b/drivers/cxl/core/hdm.c
> > @@ -242,3 +242,201 @@ int devm_cxl_enumerate_switch_decoders(struct cxl_port *port)
> >  	return 0;
> >  }
> >  EXPORT_SYMBOL_NS_GPL(devm_cxl_enumerate_switch_decoders, CXL);
> > +
> > +#define COMMIT_TIMEOUT_MS 10
> > +static int wait_for_commit(struct cxl_decoder *cxld)
> > +{
> > +	struct cxl_port *port = to_cxl_port(cxld->dev.parent);
> > +	const unsigned long start = jiffies;
> > +	struct cxl_port_state *cxlps;
> > +	void __iomem *hdm_decoder;
> > +	unsigned long end = start;
> > +	u32 ctrl;
> > +
> > +	cxlps = dev_get_drvdata(&port->dev);
> > +	hdm_decoder = cxlps->regs.hdm_decoder;
> > +
> > +	do {
> > +		end = jiffies;
> > +		ctrl = readl(hdm_decoder +
> > +			     CXL_HDM_DECODER0_CTRL_OFFSET(cxld->id));
> > +		if (FIELD_GET(CXL_HDM_DECODER0_CTRL_COMMITTED, ctrl))
> > +			break;
> > +
> > +		if (time_after(end, start + COMMIT_TIMEOUT_MS)) {
> > +			dev_err(&cxld->dev, "HDM decoder commit timeout %x\n", ctrl);
> > +			return -ETIMEDOUT;
> > +		}
> > +		if ((ctrl & CXL_HDM_DECODER0_CTRL_COMMIT_ERROR) != 0) {
> > +			dev_err(&cxld->dev, "HDM decoder commit error %x\n", ctrl);
> > +			return -ENXIO;
> > +		}
> > +	} while (FIELD_GET(CXL_HDM_DECODER0_CTRL_COMMITTED, ctrl));
> 
> Hi Ben,
> 
> Thanks for posting this btw - it's very helpful indeed for hammering out bugs
> in the qemu code and to identify what isn't there yet.
> 
> Took me a while to work out how this seemed to succeed on QEMU with no
> implementation of the commit for the host bridges (just adding that now ;)
> Reason is this condition is inverse of what I think you intend.
> 
> Given you have an exit condition above this could probably just be a while (1)
> loop.
> 
> Jonathan

Quick response without looking at code. I thought I did implement this in QEMU,
but you're correct that the logic is inverted. If you have a QEMU branch for me
to use when I fix this, please let me know.

> 
> > +
> > +	return 0;
> > +}
> > +
> > +/**
> > + * cxl_commit_decoder() - Program a configured cxl_decoder
> > + * @cxld: The preconfigured cxl decoder.
> > + *
> > + * A cxl decoder that is to be committed should have been earmarked as enabled.
> > + * This mechanism acts as a soft reservation on the decoder.
> > + *
> > + * Returns 0 if commit was successful, negative error code otherwise.
> > + */
> > +int cxl_commit_decoder(struct cxl_decoder *cxld)
> > +{
> > +	u32 ctrl, tl_lo, tl_hi, base_lo, base_hi, size_lo, size_hi;
> > +	struct cxl_port *port = to_cxl_port(cxld->dev.parent);
> > +	struct cxl_port_state *cxlps;
> > +	void __iomem *hdm_decoder;
> > +	int rc;
> > +
> > +	/*
> > +	 * Decoder flags are entirely software controlled and therefore this
> > +	 * case is purely a driver bug.
> > +	 */
> > +	if (dev_WARN_ONCE(&port->dev, (cxld->flags & CXL_DECODER_F_ENABLE) != 0,
> > +			  "Invalid %s enable state\n", dev_name(&cxld->dev)))
> > +		return -ENXIO;
> > +
> > +	cxlps = dev_get_drvdata(&port->dev);
> > +	hdm_decoder = cxlps->regs.hdm_decoder;
> > +	ctrl = readl(hdm_decoder + CXL_HDM_DECODER0_CTRL_OFFSET(cxld->id));
> > +
> > +	/*
> > +	 * A decoder that's currently active cannot be changed without the
> > +	 * system being quiesced. While the driver should prevent against this,
> > +	 * for a variety of reasons the hardware might not be in sync with the
> > +	 * hardware and so, do not splat on error.
> > +	 */
> > +	size_hi = readl(hdm_decoder +
> > +			CXL_HDM_DECODER0_SIZE_HIGH_OFFSET(cxld->id));
> > +	size_lo =
> > +		readl(hdm_decoder + CXL_HDM_DECODER0_SIZE_LOW_OFFSET(cxld->id));
> > +	if (FIELD_GET(CXL_HDM_DECODER0_CTRL_COMMITTED, ctrl) &&
> > +	    (size_lo + size_hi)) {
> > +		dev_err(&port->dev, "Tried to change an active decoder (%s)\n",
> > +			dev_name(&cxld->dev));
> > +		return -EBUSY;
> > +	}
> > +
> > +	u32p_replace_bits(&ctrl, 8 - ilog2(cxld->interleave_granularity),
> > +			  CXL_HDM_DECODER0_CTRL_IG_MASK);
> > +	u32p_replace_bits(&ctrl, ilog2(cxld->interleave_ways),
> > +			  CXL_HDM_DECODER0_CTRL_IW_MASK);
> > +	u32p_replace_bits(&ctrl, 1, CXL_HDM_DECODER0_CTRL_COMMIT);
> > +
> > +	/* TODO: set based on type */
> > +	u32p_replace_bits(&ctrl, 1, CXL_HDM_DECODER0_CTRL_TYPE);
> > +
> > +	base_lo = FIELD_PREP(GENMASK(31, 28),
> > +			     (u32)(cxld->decoder_range.start & 0xffffffff));
> > +	base_hi = FIELD_PREP(~0, (u32)(cxld->decoder_range.start >> 32));
> > +
> > +	size_lo = (u32)(range_len(&cxld->decoder_range)) & GENMASK(31, 28);
> > +	size_hi = (u32)((range_len(&cxld->decoder_range) >> 32));
> > +
> > +	if (cxld->nr_targets > 0) {
> > +		tl_lo |= FIELD_PREP(GENMASK(7, 0), cxld->target[0]->port_id);
> > +		if (cxld->interleave_ways > 1)
> > +			tl_lo |= FIELD_PREP(GENMASK(15, 8),
> > +					    cxld->target[1]->port_id);
> > +		if (cxld->interleave_ways > 2)
> > +			tl_lo |= FIELD_PREP(GENMASK(23, 16),
> > +					    cxld->target[2]->port_id);
> > +		if (cxld->interleave_ways > 3)
> > +			tl_lo |= FIELD_PREP(GENMASK(31, 24),
> > +					    cxld->target[3]->port_id);
> > +		if (cxld->interleave_ways > 4)
> > +			tl_hi |= FIELD_PREP(GENMASK(7, 0),
> > +					    cxld->target[4]->port_id);
> > +		if (cxld->interleave_ways > 5)
> > +			tl_hi |= FIELD_PREP(GENMASK(15, 8),
> > +					    cxld->target[5]->port_id);
> > +		if (cxld->interleave_ways > 6)
> > +			tl_hi |= FIELD_PREP(GENMASK(23, 16),
> > +					    cxld->target[6]->port_id);
> > +		if (cxld->interleave_ways > 7)
> > +			tl_hi |= FIELD_PREP(GENMASK(31, 24),
> > +					    cxld->target[7]->port_id);
> > +
> > +		writel(tl_hi, hdm_decoder + CXL_HDM_DECODER0_TL_HIGH(cxld->id));
> > +		writel(tl_lo, hdm_decoder + CXL_HDM_DECODER0_TL_LOW(cxld->id));
> > +	}
> > +
> > +	writel(size_hi,
> > +	       hdm_decoder + CXL_HDM_DECODER0_SIZE_HIGH_OFFSET(cxld->id));
> > +	writel(size_lo,
> > +	       hdm_decoder + CXL_HDM_DECODER0_SIZE_LOW_OFFSET(cxld->id));
> > +	writel(base_hi,
> > +	       hdm_decoder + CXL_HDM_DECODER0_BASE_HIGH_OFFSET(cxld->id));
> > +	writel(base_lo,
> > +	       hdm_decoder + CXL_HDM_DECODER0_BASE_LOW_OFFSET(cxld->id));
> > +	writel(ctrl, hdm_decoder + CXL_HDM_DECODER0_CTRL_OFFSET(cxld->id));
> > +
> > +	rc = wait_for_commit(cxld);
> > +	if (rc)
> > +		return rc;
> > +
> > +	cxld->flags |= CXL_DECODER_F_ENABLE;
> > +
> > +#define DPORT_TL_STR "%d %d %d %d %d %d %d %d"
> > +#define DPORT(i)                                                               \
> > +	(cxld->nr_targets && cxld->interleave_ways > (i)) ?                    \
> > +		      cxld->target[(i)]->port_id :                                   \
> > +		      -1
> > +#define DPORT_TL                                                               \
> > +	DPORT(0), DPORT(1), DPORT(2), DPORT(3), DPORT(4), DPORT(5), DPORT(6),  \
> > +		DPORT(7)
> > +
> > +	dev_dbg(&port->dev,
> > +		"%s\n\tBase %pa\n\tSize %llu\n\tIG %u\n\tIW %u\n\tTargetList: " DPORT_TL_STR,
> > +		dev_name(&cxld->dev), &cxld->decoder_range.start,
> > +		range_len(&cxld->decoder_range), cxld->interleave_granularity,
> > +		cxld->interleave_ways, DPORT_TL);
> > +#undef DPORT_TL
> > +#undef DPORT
> > +#undef DPORT_TL_STR
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(cxl_commit_decoder);
> > +
> > +/**
> > + * cxl_disable_decoder() - Disables a decoder
> > + * @cxld: The active cxl decoder.
> > + *
> > + * CXL decoders (as of 2.0 spec) have no way to deactivate them other than to
> > + * set the size of the HDM to 0. This function will clear all registers, and if
> > + * the decoder is active, commit the 0'd out registers.
> > + */
> > +void cxl_disable_decoder(struct cxl_decoder *cxld)
> > +{
> > +	struct cxl_port *port = to_cxl_port(cxld->dev.parent);
> > +	struct cxl_port_state *cxlps;
> > +	void __iomem *hdm_decoder;
> > +	u32 ctrl;
> > +
> > +	cxlps = dev_get_drvdata(&port->dev);
> > +	hdm_decoder = cxlps->regs.hdm_decoder;
> > +	ctrl = readl(hdm_decoder + CXL_HDM_DECODER0_CTRL_OFFSET(cxld->id));
> > +
> > +	if (dev_WARN_ONCE(&port->dev, (cxld->flags & CXL_DECODER_F_ENABLE) == 0,
> > +			  "Invalid decoder enable state\n"))
> > +		return;
> > +
> > +	/* There's no way to "uncommit" a committed decoder, only 0 size it */
> > +	writel(0, hdm_decoder + CXL_HDM_DECODER0_TL_HIGH(cxld->id));
> > +	writel(0, hdm_decoder + CXL_HDM_DECODER0_TL_LOW(cxld->id));
> > +	writel(0, hdm_decoder + CXL_HDM_DECODER0_SIZE_HIGH_OFFSET(cxld->id));
> > +	writel(0, hdm_decoder + CXL_HDM_DECODER0_SIZE_LOW_OFFSET(cxld->id));
> > +	writel(0, hdm_decoder + CXL_HDM_DECODER0_BASE_HIGH_OFFSET(cxld->id));
> > +	writel(0, hdm_decoder + CXL_HDM_DECODER0_BASE_LOW_OFFSET(cxld->id));
> > +
> > +	/* If the device isn't actually active, just zero out all the fields */
> > +	if (FIELD_GET(CXL_HDM_DECODER0_CTRL_COMMITTED, ctrl))
> > +		writel(CXL_HDM_DECODER0_CTRL_COMMIT,
> > +		       hdm_decoder + CXL_HDM_DECODER0_CTRL_OFFSET(cxld->id));
> > +}
> > +EXPORT_SYMBOL_GPL(cxl_disable_decoder);
> > diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> > index 79bca9a8246c..587b75f7fa53 100644
> > --- a/drivers/cxl/cxl.h
> > +++ b/drivers/cxl/cxl.h
> > @@ -54,6 +54,7 @@
> >  #define   CXL_HDM_DECODER0_CTRL_IW_MASK GENMASK(7, 4)
> >  #define   CXL_HDM_DECODER0_CTRL_COMMIT BIT(9)
> >  #define   CXL_HDM_DECODER0_CTRL_COMMITTED BIT(10)
> > +#define   CXL_HDM_DECODER0_CTRL_COMMIT_ERROR BIT(11)
> >  #define   CXL_HDM_DECODER0_CTRL_TYPE BIT(12)
> >  #define CXL_HDM_DECODER0_TL_LOW(i) (0x20 * (i) + 0x24)
> >  #define CXL_HDM_DECODER0_TL_HIGH(i) (0x20 * (i) + 0x28)
> > @@ -364,6 +365,8 @@ int devm_cxl_add_dport(struct cxl_port *port, struct device *dport, int port_id,
> >  struct cxl_dport *cxl_find_dport_by_dev(struct cxl_port *port,
> >  					const struct device *dev);
> >  struct cxl_port *ep_find_cxl_port(struct cxl_memdev *cxlmd, unsigned int depth);
> > +int cxl_commit_decoder(struct cxl_decoder *cxld);
> > +void cxl_disable_decoder(struct cxl_decoder *cxld);
> >  
> >  struct cxl_decoder *to_cxl_decoder(struct device *dev);
> >  bool is_cxl_decoder(struct device *dev);
> > diff --git a/drivers/cxl/region.c b/drivers/cxl/region.c
> > index 3120b65b0bc5..fd82d37ba573 100644
> > --- a/drivers/cxl/region.c
> > +++ b/drivers/cxl/region.c
> > @@ -580,10 +580,30 @@ static void cleanup_staged_decoders(struct cxl_region *region)
> >  	}
> >  }
> >  
> > -static int bind_region(const struct cxl_region *region)
> > +static int bind_region(struct cxl_region *region)
> >  {
> > -	/* TODO: */
> > -	return 0;
> > +	struct cxl_decoder *cxld, *d;
> > +	int rc;
> > +
> > +	list_for_each_entry_safe(cxld, d, &region->staged_list, region_link) {
> > +		rc = cxl_commit_decoder(cxld);
> > +		if (!rc)
> > +			list_move_tail(&cxld->region_link, &region->commit_list);
> > +		else
> > +			break;
> > +	}
> > +
> > +	list_for_each_entry_safe(cxld, d, &region->commit_list, region_link) {
> > +		if (rc)
> > +			cxl_disable_decoder(cxld);
> > +		list_del(&cxld->region_link);
> > +	}
> > +
> > +	if (rc)
> > +		cleanup_staged_decoders((struct cxl_region *)region);
> > +
> > +	BUG_ON(!list_empty(&region->staged_list));
> > +	return rc;
> >  }
> >  
> >  static int cxl_region_probe(struct device *dev)
> > @@ -650,9 +670,22 @@ static int cxl_region_probe(struct device *dev)
> >  	return ret;
> >  }
> >  
> > +static void cxl_region_remove(struct device *dev)
> > +{
> > +	struct cxl_region *region = to_cxl_region(dev);
> > +	struct cxl_decoder *cxld, *d;
> > +
> > +	list_for_each_entry_safe(cxld, d, &region->commit_list, region_link) {
> > +		cxl_disable_decoder(cxld);
> > +		list_del(&cxld->region_link);
> > +		cxl_put_decoder(cxld);
> > +	}
> > +}
> > +
> >  static struct cxl_driver cxl_region_driver = {
> >  	.name = "cxl_region",
> >  	.probe = cxl_region_probe,
> > +	.remove = cxl_region_remove,
> >  	.id = CXL_DEVICE_REGION,
> >  };
> >  module_cxl_driver(cxl_region_driver);
>