Re: [RFC PATCH 1/4] cxl: Register devices for CXL Hotness Monitoring Units (CHMU)

From: Jonathan Cameron
Date: Thu Jun 19 2025 - 06:11:36 EST

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In reply to: Yuquan Wang: "Re: [RFC PATCH 1/4] cxl: Register devices for CXL Hotness Monitoring Units (CHMU)"
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On Thu, 19 Jun 2025 09:47:00 +0800
Yuquan Wang <wangyuquan1236@xxxxxxxxxxxxxx> wrote:

> On Thu, Nov 21, 2024 at 10:18:42AM +0000, Jonathan Cameron wrote:
> > Basic registration using similar approach to how the CPMUs
> > are registered.
> >
> > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
> > ---
> > drivers/cxl/core/Makefile | 1 +
> > drivers/cxl/core/hmu.c | 64 +++++++++++++++++++++++++++++++++++++++
> > drivers/cxl/core/regs.c | 14 +++++++++
> > drivers/cxl/cxl.h | 4 +++
> > drivers/cxl/cxlpci.h | 1 +
> > drivers/cxl/hmu.h | 23 ++++++++++++++
> > drivers/cxl/pci.c | 26 +++++++++++++++-
> > 7 files changed, 132 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/cxl/core/Makefile b/drivers/cxl/core/Makefile
> > index 9259bcc6773c..d060abb773ae 100644
> > --- a/drivers/cxl/core/Makefile
> > +++ b/drivers/cxl/core/Makefile
> > @@ -12,6 +12,7 @@ cxl_core-y += memdev.o
> > cxl_core-y += mbox.o
> > cxl_core-y += pci.o
> > cxl_core-y += hdm.o
> > +cxl_core-y += hmu.o
> > cxl_core-y += pmu.o
> > cxl_core-y += cdat.o
> > cxl_core-$(CONFIG_TRACING) += trace.o
> > diff --git a/drivers/cxl/core/hmu.c b/drivers/cxl/core/hmu.c
> > new file mode 100644
> > index 000000000000..3ee938bb6c05
> > --- /dev/null
> > +++ b/drivers/cxl/core/hmu.c
> > @@ -0,0 +1,64 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/* Copyright(c) 2024 Huawei. All rights reserved. */
> > +
> > +#include <linux/device.h>
> > +#include <linux/slab.h>
> > +#include <linux/idr.h>
> > +#include <cxlmem.h>
> > +#include <hmu.h>
> > +#include <cxl.h>
> > +#include "core.h"
> > +
> > +static void cxl_hmu_release(struct device *dev)
> > +{
> > + struct cxl_hmu *hmu = to_cxl_hmu(dev);
> > +
> > + kfree(hmu);
> > +}
> > +
> > +const struct device_type cxl_hmu_type = {
> > + .name = "cxl_hmu",
> > + .release = cxl_hmu_release,
> > +};
> > +
> > +static void remove_dev(void *dev)
> > +{
> > + device_unregister(dev);
> > +}
> > +
> > +int devm_cxl_hmu_add(struct device *parent, struct cxl_hmu_regs *regs,
> > + int assoc_id, int index)
> > +{
> > + struct cxl_hmu *hmu;
> > + struct device *dev;
> > + int rc;
> > +
> > + hmu = kzalloc(sizeof(*hmu), GFP_KERNEL);
> > + if (!hmu)
> > + return -ENOMEM;
> > +
> > + hmu->assoc_id = assoc_id;
> > + hmu->index = index;
> > + hmu->base = regs->hmu;
> > + dev = &hmu->dev;
> > + device_initialize(dev);
> > + device_set_pm_not_required(dev);
> > + dev->parent = parent;
> > + dev->bus = &cxl_bus_type;
> > + dev->type = &cxl_hmu_type;
> > + rc = dev_set_name(dev, "hmu_mem%d.%d", assoc_id, index);
> > + if (rc)
> > + goto err;
> > +
> > + rc = device_add(dev);
> > + if (rc)
> > + goto err;
> > +
> > + return devm_add_action_or_reset(parent, remove_dev, dev);
> > +
> > +err:
> > + put_device(&hmu->dev);
> > + return rc;
> > +}
> > +EXPORT_SYMBOL_NS_GPL(devm_cxl_hmu_add, CXL);
> > +
> > diff --git a/drivers/cxl/core/regs.c b/drivers/cxl/core/regs.c
> > index e1082e749c69..c12afaa6ef98 100644
> > --- a/drivers/cxl/core/regs.c
> > +++ b/drivers/cxl/core/regs.c
> > @@ -401,6 +401,20 @@ int cxl_map_pmu_regs(struct cxl_register_map *map, struct cxl_pmu_regs *regs)
> > }
> > EXPORT_SYMBOL_NS_GPL(cxl_map_pmu_regs, CXL);
> >
> > +int cxl_map_hmu_regs(struct cxl_register_map *map, struct cxl_hmu_regs *regs)
> > +{
> > + struct device *dev = map->host;
> > + resource_size_t phys_addr;
> > +
> > + phys_addr = map->resource;
> > + regs->hmu = devm_cxl_iomap_block(dev, phys_addr, map->max_size);
> I applied CHMU patch on 6.15.0 kernel and I tried to boot the virt with
> one cxl root port and one device (jic23/cxl-2025-06-10), then the dmesg shows
> "Failed to request region 0x10210000-0x1023ffff". I guess it is caused by the
> 'map->max_size'(0x30000) is large and the resource has been allocated by CPMU regs.
> I tried to change it to 0x10000, the hmu_mem0.0 could be created as normal.

Ah. I was meaning to post an updated version of this series just to fix the
bug you've hit here but forgot to do so! Sorry about that.

I need to figure out if there is a more elegant way to do this but in meantime
here is what I'm carrying on top of these posted series. It's a fairly horrible
bit of layering as we need the generic code to know to poke around inside a temporary
mapping just to get the size that it should iomap.

From fadffb32ed302dfb6dec4497214e1d3b39450f8b Mon Sep 17 00:00:00 2001
From: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
Date: Thu, 17 Apr 2025 11:02:07 +0100
Subject: [PATCH] Fix up sizing of CHMU issue

---
drivers/cxl/core/regs.c | 16 ++++++++++++++--
drivers/cxl/cxlpci.h | 7 +++++++
drivers/cxl/hmu.c | 6 ------
3 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/drivers/cxl/core/regs.c b/drivers/cxl/core/regs.c
index 925870c4e494..5ae31696bf8b 100644
--- a/drivers/cxl/core/regs.c
+++ b/drivers/cxl/core/regs.c
@@ -416,10 +416,22 @@ EXPORT_SYMBOL_NS_GPL(cxl_map_pmu_regs, "CXL");
int cxl_map_hmu_regs(struct cxl_register_map *map, struct cxl_hmu_regs *regs)
{
struct device *dev = map->host;
- resource_size_t phys_addr;
+ u64 __iomem *poke;
+ u64 common_cap[2];
+ resource_size_t phys_addr, phys_size;

phys_addr = map->resource;
- regs->hmu = devm_cxl_iomap_block(dev, phys_addr, map->max_size);
+ /* Finding out the size of a CHMU means poking around inside */
+ poke = ioremap(phys_addr, sizeof(common_cap));
+ if (!poke) {
+ return -ENOMEM;
+ }
+ common_cap[0] = le64_to_cpu(readq(poke));
+ common_cap[1] = le64_to_cpu(readq(poke + 1));
+ iounmap(poke);
+ phys_size = FIELD_GET(CHMU_COMMON_CAP0_NUMINST_MSK, common_cap[0]) *
+ FIELD_GET(CHMU_COMMON_CAP1_INSTLEN_MSK, common_cap[1]) + 0x10;
+ regs->hmu = devm_cxl_iomap_block(dev, phys_addr, phys_size);
if (!regs->hmu)
return -ENOMEM;

diff --git a/drivers/cxl/cxlpci.h b/drivers/cxl/cxlpci.h
index f7b902eab288..a91407292aea 100644
--- a/drivers/cxl/cxlpci.h
+++ b/drivers/cxl/cxlpci.h
@@ -77,6 +77,13 @@ enum cxl_regloc_type {
CXL_REGLOC_RBI_TYPES
};

+/* A few CHMU registers are needed to establish size */
+#define CHMU_COMMON_CAP0_REG 0x00
+#define CHMU_COMMON_CAP0_VER_MSK GENMASK(3, 0)
+#define CHMU_COMMON_CAP0_NUMINST_MSK GENMASK(15, 8)
+#define CHMU_COMMON_CAP1_REG 0x08
+#define CHMU_COMMON_CAP1_INSTLEN_MSK GENMASK(15, 0)
+
/*
* Table Access DOE, CDAT Read Entry Response
*
diff --git a/drivers/cxl/hmu.c b/drivers/cxl/hmu.c
index 1a7a0f60a6ad..a1953e8750c8 100644
--- a/drivers/cxl/hmu.c
+++ b/drivers/cxl/hmu.c
@@ -27,12 +27,6 @@
#include "cxl.h"
#include "hmu.h"

-#define CHMU_COMMON_CAP0_REG 0x00
-#define CHMU_COMMON_CAP0_VER_MSK GENMASK(3, 0)
-#define CHMU_COMMON_CAP0_NUMINST_MSK GENMASK(15, 8)
-#define CHMU_COMMON_CAP1_REG 0x08
-#define CHMU_COMMON_CAP1_INSTLEN_MSK GENMASK(15, 0)
-
/* Register offsets within instance */
#define CHMU_INST0_CAP0_REG 0x00
#define CHMU_INST0_CAP0_MSI_N_MSK GENMASK(3, 0)
--
2.48.1

> > + if (!regs->hmu)
> > + return -ENOMEM;
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL_NS_GPL(cxl_map_hmu_regs, CXL);
> > +
> > static int cxl_map_regblock(struct cxl_register_map *map)
> > {
> > struct device *host = map->host;
> > diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> > index 5406e3ab3d4a..8172bc1f7a8d 100644
> > --- a/drivers/cxl/cxl.h
> > +++ b/drivers/cxl/cxl.h
> > @@ -227,6 +227,9 @@ struct cxl_regs {
> > struct_group_tagged(cxl_pmu_regs, pmu_regs,
> > void __iomem *pmu;
> > );
> > + struct_group_tagged(cxl_hmu_regs, hmu_regs,
> > + void __iomem *hmu;
> > + );
> >
> > /*
> > * RCH downstream port specific RAS register
> > @@ -292,6 +295,7 @@ int cxl_map_component_regs(const struct cxl_register_map *map,
> > unsigned long map_mask);
> > int cxl_map_device_regs(const struct cxl_register_map *map,
> > struct cxl_device_regs *regs);
> > +int cxl_map_hmu_regs(struct cxl_register_map *map, struct cxl_hmu_regs *regs);
> > int cxl_map_pmu_regs(struct cxl_register_map *map, struct cxl_pmu_regs *regs);
> >
> > enum cxl_regloc_type;
> > diff --git a/drivers/cxl/cxlpci.h b/drivers/cxl/cxlpci.h
> > index 4da07727ab9c..71f5e9620137 100644
> > --- a/drivers/cxl/cxlpci.h
> > +++ b/drivers/cxl/cxlpci.h
> > @@ -67,6 +67,7 @@ enum cxl_regloc_type {
> > CXL_REGLOC_RBI_VIRT,
> > CXL_REGLOC_RBI_MEMDEV,
> > CXL_REGLOC_RBI_PMU,
> > + CXL_REGLOC_RBI_HMU,
> > CXL_REGLOC_RBI_TYPES
> > };
> >
> > diff --git a/drivers/cxl/hmu.h b/drivers/cxl/hmu.h
> > new file mode 100644
> > index 000000000000..c4798ed9764b
> > --- /dev/null
> > +++ b/drivers/cxl/hmu.h
> > @@ -0,0 +1,23 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +/*
> > + * Copyright(c) 2024 Huawei
> > + * CXL Specification rev 3.2 Setion 8.2.8 (CHMU Register Interface)
> > + */
> > +#ifndef CXL_HMU_H
> > +#define CXL_HMU_H
> > +#include <linux/device.h>
> > +
> > +#define CXL_HMU_REGMAP_SIZE 0xe00 /* Table 8-32 CXL 3.0 specification */
> > +struct cxl_hmu {
> > + struct device dev;
> > + void __iomem *base;
> > + int assoc_id;
> > + int index;
> > +};
> > +
> > +#define to_cxl_hmu(dev) container_of(dev, struct cxl_hmu, dev)
> > +struct cxl_hmu_regs;
> > +int devm_cxl_hmu_add(struct device *parent, struct cxl_hmu_regs *regs,
> > + int assoc_id, int idx);
> > +
> > +#endif
> > diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> > index 188412d45e0d..e89ea9d3f007 100644
> > --- a/drivers/cxl/pci.c
> > +++ b/drivers/cxl/pci.c
> > @@ -15,6 +15,7 @@
> > #include "cxlmem.h"
> > #include "cxlpci.h"
> > #include "cxl.h"
> > +#include "hmu.h"
> > #include "pmu.h"
> >
> > /**
> > @@ -814,7 +815,7 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> > struct cxl_dev_state *cxlds;
> > struct cxl_register_map map;
> > struct cxl_memdev *cxlmd;
> > - int i, rc, pmu_count;
> > + int i, rc, hmu_count, pmu_count;
> > bool irq_avail;
> >
> > /*
> > @@ -938,6 +939,29 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> > }
> > }
> >
> > + hmu_count = cxl_count_regblock(pdev, CXL_REGLOC_RBI_HMU);
> > + for (i = 0; i < hmu_count; i++) {
> > + struct cxl_hmu_regs hmu_regs;
> > +
> > + rc = cxl_find_regblock_instance(pdev, CXL_REGLOC_RBI_HMU, &map, i);
> > + if (rc) {
> > + dev_dbg(&pdev->dev, "Could not find HMU regblock\n");
> > + break;
> > + }
> > +
> > + rc = cxl_map_hmu_regs(&map, &hmu_regs);
> > + if (rc) {
> > + dev_dbg(&pdev->dev, "Could not map HMU regs\n");
> > + break;
> > + }
> > +
> > + rc = devm_cxl_hmu_add(cxlds->dev, &hmu_regs, cxlmd->id, i);
> > + if (rc) {
> > + dev_dbg(&pdev->dev, "Could not add HMU instance\n");
> > + break;
> > + }
> > + }
> > +
> > rc = cxl_event_config(host_bridge, mds, irq_avail);
> > if (rc)
> > return rc;
> > --
> > 2.43.0
> >
>
>

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