diff mbox series

[v2,14/28] cxl/hdm: Add sysfs attributes for interleave ways + granularity

Message ID 165784332235.1758207.7185062713652694607.stgit@dwillia2-xfh.jf.intel.com
State Accepted
Commit 538831f1beb818c93e5879bf19de37d89ec88ed6
Headers show
Series CXL PMEM Region Provisioning | expand

Commit Message

Dan Williams July 15, 2022, 12:02 a.m. UTC
From: Ben Widawsky <bwidawsk@kernel.org>

The region provisioning flow involves selecting interleave ways +
granularity settings for a region, and then programming the decoder
topology to meet those constraints, if possible. For example, root
decoders set the minimum interleave ways + granularity for any hosted
regions.

Given decoder programming is not atomic and collisions can occur between
multiple requesting regions userspace will be responsible for conflict
resolution and it needs these attributes to make those decisions.

Signed-off-by: Ben Widawsky <bwidawsk@kernel.org>
[djbw: reword changelog, make read-only, add sysfs ABI documentaion]
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 Documentation/ABI/testing/sysfs-bus-cxl |   27 +++++++++++++++++++++++++++
 drivers/cxl/core/port.c                 |   23 +++++++++++++++++++++++
 2 files changed, 50 insertions(+)

Comments

Jonathan Cameron July 20, 2022, 4:58 p.m. UTC | #1
On Thu, 14 Jul 2022 17:02:02 -0700
Dan Williams <dan.j.williams@intel.com> wrote:

> From: Ben Widawsky <bwidawsk@kernel.org>
> 
> The region provisioning flow involves selecting interleave ways +
> granularity settings for a region, and then programming the decoder
> topology to meet those constraints, if possible. For example, root
> decoders set the minimum interleave ways + granularity for any hosted
> regions.
> 
> Given decoder programming is not atomic and collisions can occur between
> multiple requesting regions userspace will be responsible for conflict
> resolution and it needs these attributes to make those decisions.
> 
> Signed-off-by: Ben Widawsky <bwidawsk@kernel.org>
> [djbw: reword changelog, make read-only, add sysfs ABI documentaion]
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
diff mbox series

Patch

diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl
index 9b6cc7cdc73b..0362ae98218e 100644
--- a/Documentation/ABI/testing/sysfs-bus-cxl
+++ b/Documentation/ABI/testing/sysfs-bus-cxl
@@ -230,3 +230,30 @@  Description:
 		allocations are enforced to occur in increasing 'decoderX.Y/id'
 		order and frees are enforced to occur in decreasing
 		'decoderX.Y/id' order.
+
+
+What:		/sys/bus/cxl/devices/decoderX.Y/interleave_ways
+Date:		May, 2022
+KernelVersion:	v5.20
+Contact:	linux-cxl@vger.kernel.org
+Description:
+		(RO) The number of targets across which this decoder's host
+		physical address (HPA) memory range is interleaved. The device
+		maps every Nth block of HPA (of size ==
+		'interleave_granularity') to consecutive DPA addresses. The
+		decoder's position in the interleave is determined by the
+		device's (endpoint or switch) switch ancestry. For root
+		decoders their interleave is specified by platform firmware and
+		they only specify a downstream target order for host bridges.
+
+
+What:		/sys/bus/cxl/devices/decoderX.Y/interleave_granularity
+Date:		May, 2022
+KernelVersion:	v5.20
+Contact:	linux-cxl@vger.kernel.org
+Description:
+		(RO) The number of consecutive bytes of host physical address
+		space this decoder claims at address N before the decode rotates
+		to the next target in the interleave at address N +
+		interleave_granularity (assuming N is aligned to
+		interleave_granularity).
diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index b2c44e7ef6a8..a43735f349d6 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -260,10 +260,33 @@  static ssize_t dpa_size_store(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR_RW(dpa_size);
 
+static ssize_t interleave_granularity_show(struct device *dev,
+					   struct device_attribute *attr,
+					   char *buf)
+{
+	struct cxl_decoder *cxld = to_cxl_decoder(dev);
+
+	return sysfs_emit(buf, "%d\n", cxld->interleave_granularity);
+}
+
+static DEVICE_ATTR_RO(interleave_granularity);
+
+static ssize_t interleave_ways_show(struct device *dev,
+				    struct device_attribute *attr, char *buf)
+{
+	struct cxl_decoder *cxld = to_cxl_decoder(dev);
+
+	return sysfs_emit(buf, "%d\n", cxld->interleave_ways);
+}
+
+static DEVICE_ATTR_RO(interleave_ways);
+
 static struct attribute *cxl_decoder_base_attrs[] = {
 	&dev_attr_start.attr,
 	&dev_attr_size.attr,
 	&dev_attr_locked.attr,
+	&dev_attr_interleave_granularity.attr,
+	&dev_attr_interleave_ways.attr,
 	NULL,
 };