Re: [PATCH v16 10/18] cxl: Build register block helpers into the kernel

[Richard Cheng]

On Thu, Oct 29, 2026 at 02:56:55PM +0800, Srirangan Madhavan wrote:
> Build register discovery with the built-in HDM helpers so PCI enumeration
> can use it even when cxl_core is modular. Export the interfaces used by
> cxl_core and preserve the BAR and offset in the register map.
> 
> Signed-off-by: Srirangan Madhavan <smadhavan@xxxxxxxxxx>

Reviewed-by: Richard Cheng <icheng@xxxxxxxxxx>

> ---
>  drivers/cxl/core/Makefile |  3 +--
>  drivers/cxl/core/regs.c   |  9 +++++++++
>  drivers/cxl/cxl.h         |  3 ---
>  include/cxl/cxl.h         |  6 ++++++
>  include/cxl/pci.h         | 13 +++++++++++++
>  tools/testing/cxl/Kbuild  |  1 -
>  6 files changed, 29 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/cxl/core/Makefile b/drivers/cxl/core/Makefile
> index 9971efb237fb..9a77e68d44ce 100644
> --- a/drivers/cxl/core/Makefile
> +++ b/drivers/cxl/core/Makefile
> @@ -1,6 +1,6 @@
>  # SPDX-License-Identifier: GPL-2.0
>  obj-$(CONFIG_CXL_BUS) += cxl_core.o
> -obj-$(subst m,y,$(CONFIG_CXL_BUS)) += hdm_regs.o hdm_state.o
> +obj-$(subst m,y,$(CONFIG_CXL_BUS)) += hdm_regs.o hdm_state.o regs.o
>  obj-$(CONFIG_CXL_SUSPEND) += suspend.o
>  
>  ccflags-y += -I$(srctree)/drivers/cxl
> @@ -8,7 +8,6 @@ CFLAGS_trace.o = -DTRACE_INCLUDE_PATH=. -I$(src)
>  
>  cxl_core-y := port.o
>  cxl_core-y += pmem.o
> -cxl_core-y += regs.o
>  cxl_core-y += memdev.o
>  cxl_core-y += mbox.o
>  cxl_core-y += pci.o
> diff --git a/drivers/cxl/core/regs.c b/drivers/cxl/core/regs.c
> index 20c2d9fbcfe7..def3c20d1a7a 100644
> --- a/drivers/cxl/core/regs.c
> +++ b/drivers/cxl/core/regs.c
> @@ -200,6 +200,7 @@ void __iomem *devm_cxl_iomap_block(struct device *dev, resource_size_t addr,
>  
>  	return ret_val;
>  }
> +EXPORT_SYMBOL_FOR_MODULES(devm_cxl_iomap_block, "cxl_core");
>  
>  int cxl_map_component_regs(const struct cxl_register_map *map,
>  			   struct cxl_component_regs *regs,
> @@ -285,6 +286,8 @@ static bool cxl_decode_regblock(struct pci_dev *pdev, u32 reg_lo, u32 reg_hi,
>  	}
>  
>  	map->reg_type = reg_type;
> +	map->bar = bar;
> +	map->bar_offset = offset;
>  	map->resource = pci_resource_start(pdev, bar) + offset;
>  	map->max_size = pci_resource_len(pdev, bar) - offset;
>  	return true;
> @@ -309,6 +312,7 @@ static int __cxl_find_regblock_instance(struct pci_dev *pdev, enum cxl_regloc_ty
>  	*map = (struct cxl_register_map) {
>  		.host = &pdev->dev,
>  		.resource = CXL_RESOURCE_NONE,
> +		.bar = -1,
>  	};
>  
>  	regloc = pci_find_dvsec_capability(pdev, PCI_VENDOR_ID_CXL,
> @@ -339,6 +343,8 @@ static int __cxl_find_regblock_instance(struct pci_dev *pdev, enum cxl_regloc_ty
>  	}
>  
>  	map->resource = CXL_RESOURCE_NONE;
> +	map->bar = -1;
> +	map->bar_offset = 0;
>  	if (index == CXL_INSTANCES_COUNT)
>  		return instance;
>  
> @@ -518,6 +524,7 @@ u16 cxl_rcrb_to_aer(struct device *dev, resource_size_t rcrb)
>  
>  	return offset;
>  }
> +EXPORT_SYMBOL_NS_GPL(cxl_rcrb_to_aer, "CXL");
>  
>  static resource_size_t cxl_rcrb_to_linkcap(struct device *dev, struct cxl_dport *dport)
>  {
> @@ -634,6 +641,7 @@ resource_size_t __rcrb_to_component(struct device *dev, struct cxl_rcrb_info *ri
>  
>  	return component_reg_phys;
>  }
> +EXPORT_SYMBOL_NS_GPL(__rcrb_to_component, "CXL");
>  
>  resource_size_t cxl_rcd_component_reg_phys(struct device *dev,
>  					   struct cxl_dport *dport)
> @@ -642,3 +650,4 @@ resource_size_t cxl_rcd_component_reg_phys(struct device *dev,
>  		return CXL_RESOURCE_NONE;
>  	return __rcrb_to_component(dev, &dport->rcrb, CXL_RCRB_UPSTREAM);
>  }
> +EXPORT_SYMBOL_NS_GPL(cxl_rcd_component_reg_phys, "CXL");
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 688350c7c5fb..ad4e80be2bd7 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -239,9 +239,6 @@ enum cxl_regloc_type;
>  int cxl_count_regblock(struct pci_dev *pdev, enum cxl_regloc_type type);
>  int cxl_find_regblock_instance(struct pci_dev *pdev, enum cxl_regloc_type type,
>  			       struct cxl_register_map *map, unsigned int index);
> -int cxl_find_regblock(struct pci_dev *pdev, enum cxl_regloc_type type,
> -		      struct cxl_register_map *map);
> -int cxl_setup_regs(struct cxl_register_map *map);
>  struct cxl_dport;
>  int cxl_dport_map_rcd_linkcap(struct pci_dev *pdev, struct cxl_dport *dport);
>  
> diff --git a/include/cxl/cxl.h b/include/cxl/cxl.h
> index 341a7c52894a..206acf5845e1 100644
> --- a/include/cxl/cxl.h
> +++ b/include/cxl/cxl.h
> @@ -27,6 +27,7 @@ enum cxl_devtype {
>  
>  struct cxl_region;
>  struct cxl_hdm_info;
> +struct pci_dev;
>  
>  enum cxl_decoder_type {
>  	CXL_DECODER_DEVMEM = 2,
> @@ -150,6 +151,8 @@ struct cxl_pmu_reg_map {
>   * @base: virtual base of the register-block-BAR + @block_offset
>   * @resource: physical resource base of the register block
>   * @max_size: maximum mapping size to perform register search
> + * @bar: PCI BAR containing the register block
> + * @bar_offset: register block offset relative to @bar
>   * @reg_type: see enum cxl_regloc_type
>   * @component_map: cxl_reg_map for component registers
>   * @device_map: cxl_reg_maps for device registers
> @@ -160,6 +163,8 @@ struct cxl_register_map {
>  	void __iomem *base;
>  	resource_size_t resource;
>  	resource_size_t max_size;
> +	int bar;
> +	resource_size_t bar_offset;
>  	u8 reg_type;
>  	union {
>  		struct cxl_component_reg_map component_map;
> @@ -168,6 +173,7 @@ struct cxl_register_map {
>  	};
>  };
>  
> +
>  /**
>   * struct cxl_dpa_perf - DPA performance property entry
>   * @dpa_range: range for DPA address
> diff --git a/include/cxl/pci.h b/include/cxl/pci.h
> index 3e0000015871..b15d7e415e27 100644
> --- a/include/cxl/pci.h
> +++ b/include/cxl/pci.h
> @@ -4,6 +4,8 @@
>  #ifndef __CXL_CXL_PCI_H__
>  #define __CXL_CXL_PCI_H__
>  
> +#include <linux/types.h>
> +
>  /* Register Block Identifier (RBI) */
>  enum cxl_regloc_type {
>  	CXL_REGLOC_RBI_EMPTY = 0,
> @@ -19,4 +21,15 @@ struct pci_dev;
>  
>  int cxl_pci_setup_regs(struct pci_dev *pdev, enum cxl_regloc_type type,
>  		       struct cxl_register_map *map);
> +int cxl_find_regblock(struct pci_dev *pdev, enum cxl_regloc_type type,
> +		      struct cxl_register_map *map);
> +int cxl_setup_regs(struct cxl_register_map *map);
> +/*
> + * CXL r4.0 sec 8.1.3.1: a CXL.mem capable device reports one or two HDM
> + * ranges. 00b is illegal when Mem_Capable is set and 11b is reserved.
> + */
> +static inline bool cxl_dvsec_hdm_count_valid(unsigned int hdm_count)
> +{
> +	return hdm_count == 1 || hdm_count == 2;
> +}
>  #endif
> diff --git a/tools/testing/cxl/Kbuild b/tools/testing/cxl/Kbuild
> index 2be1df80fcc9..e80500f457a9 100644
> --- a/tools/testing/cxl/Kbuild
> +++ b/tools/testing/cxl/Kbuild
> @@ -55,7 +55,6 @@ obj-m += cxl_core.o
>  
>  cxl_core-y := $(CXL_CORE_SRC)/port.o
>  cxl_core-y += $(CXL_CORE_SRC)/pmem.o
> -cxl_core-y += $(CXL_CORE_SRC)/regs.o
>  cxl_core-y += $(CXL_CORE_SRC)/memdev.o
>  cxl_core-y += $(CXL_CORE_SRC)/mbox.o
>  cxl_core-y += $(CXL_CORE_SRC)/pci.o
> -- 
> 2.43.0
>