Re: [PATCH v14 06/16] cxl: Move HDM decoder helpers to built-in resource code

[Dave Jiang]

On 10/1/26 2:22 AM, Srirangan Madhavan wrote:
> Move the refactored HDM programming helpers and cxl_rwsem from hdm.c to
> resource.c. Build resource.o under CONFIG_CXL_RESET so the helpers are
> available to built-in PCI code when CXL_BUS is modular. Export only the
> symbols used by cxl_core.
> 
> Signed-off-by: Srirangan Madhavan <smadhavan@xxxxxxxxxx>
> ---
>  drivers/cxl/Kconfig         |   4 ++
>  drivers/cxl/core/Makefile   |   1 +
>  drivers/cxl/core/hdm.c      |  93 -------------------------------
>  drivers/cxl/core/resource.c | 106 ++++++++++++++++++++++++++++++++++++
>  4 files changed, 111 insertions(+), 93 deletions(-)
>  create mode 100644 drivers/cxl/core/resource.c
> 
> diff --git a/drivers/cxl/Kconfig b/drivers/cxl/Kconfig
> index 80aeb0d556bd..0cd704670735 100644
> --- a/drivers/cxl/Kconfig
> +++ b/drivers/cxl/Kconfig
> @@ -6,6 +6,7 @@ menuconfig CXL_BUS
>  	select FW_UPLOAD
>  	select PCI_DOE
>  	select FIRMWARE_TABLE
> +	select CXL_RESET
>  	select NUMA_KEEP_MEMINFO if NUMA_MEMBLKS
>  	select FWCTL if CXL_FEATURES
>  	help
> @@ -244,3 +245,6 @@ config CXL_ATL
>  	depends on ACPI_PRMT && AMD_NB
>  
>  endif
> +
> +config CXL_RESET
> +	bool

Can you add a comment here for this and say something like CXL_RESET can't be 'n' when CXL_BUS is active? There are things that should always build in resource.o and later regs.o that will be under the CXL_RESET symbol with this series.

DJ

> diff --git a/drivers/cxl/core/Makefile b/drivers/cxl/core/Makefile
> index ce7213818d3c..30470799e059 100644
> --- a/drivers/cxl/core/Makefile
> +++ b/drivers/cxl/core/Makefile
> @@ -1,5 +1,6 @@
>  # SPDX-License-Identifier: GPL-2.0
>  obj-$(CONFIG_CXL_BUS) += cxl_core.o
> +obj-$(CONFIG_CXL_RESET) += resource.o
>  obj-$(CONFIG_CXL_SUSPEND) += suspend.o
>  
>  ccflags-y += -I$(srctree)/drivers/cxl
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index d3f21dfda146..629e3420ad0b 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -16,11 +16,6 @@
>   * for enumerating these registers and capabilities.
>   */
>  
> -struct cxl_rwsem cxl_rwsem = {
> -	.region = __RWSEM_INITIALIZER(cxl_rwsem.region),
> -	.dpa = __RWSEM_INITIALIZER(cxl_rwsem.dpa),
> -};
> -
>  static int add_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld)
>  {
>  	int rc;
> @@ -707,35 +702,6 @@ int cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, u64 size)
>  	return devm_add_action_or_reset(&port->dev, cxl_dpa_release, cxled);
>  }
>  
> -static void cxld_set_interleave(struct cxl_decoder_config *config, u32 *ctrl)
> -{
> -	u16 eig;
> -	u8 eiw;
> -
> -	/*
> -	 * Input validation ensures these warns never fire, but otherwise
> -	 * suppress unititalized variable usage warnings.
> -	 */
> -	if (WARN_ONCE(ways_to_eiw(config->interleave_ways, &eiw),
> -		      "invalid interleave_ways: %d\n", config->interleave_ways))
> -		return;
> -	if (WARN_ONCE(granularity_to_eig(config->interleave_granularity, &eig),
> -		      "invalid interleave_granularity: %d\n",
> -		      config->interleave_granularity))
> -		return;
> -
> -	u32p_replace_bits(ctrl, eig, CXL_HDM_DECODER0_CTRL_IG_MASK);
> -	u32p_replace_bits(ctrl, eiw, CXL_HDM_DECODER0_CTRL_IW_MASK);
> -	*ctrl |= CXL_HDM_DECODER0_CTRL_COMMIT;
> -}
> -
> -static void cxld_set_type(struct cxl_decoder_config *config, u32 *ctrl)
> -{
> -	u32p_replace_bits(ctrl,
> -			  !!(config->target_type == CXL_DECODER_HOSTONLYMEM),
> -			  CXL_HDM_DECODER0_CTRL_HOSTONLY);
> -}
> -
>  static void cxlsd_set_targets(struct cxl_switch_decoder *cxlsd, u64 *tgt)
>  {
>  	struct cxl_dport **t = &cxlsd->target[0];
> @@ -758,65 +724,6 @@ static void cxlsd_set_targets(struct cxl_switch_decoder *cxlsd, u64 *tgt)
>  		*tgt |= FIELD_PREP(GENMASK_ULL(63, 56), t[7]->port_id);
>  }
>  
> -/*
> - * Per CXL 2.0 8.2.5.12.20 Committing Decoder Programming, hardware must set
> - * committed or error within 10ms, but just be generous with 20ms to account for
> - * clock skew and other marginal behavior
> - */
> -#define COMMIT_TIMEOUT_MS 20
> -int cxld_await_commit(void __iomem *hdm, int id)
> -{
> -	u32 ctrl;
> -	int i;
> -
> -	for (i = 0; i < COMMIT_TIMEOUT_MS; i++) {
> -		ctrl = readl(hdm + CXL_HDM_DECODER0_CTRL_OFFSET(id));
> -		if (FIELD_GET(CXL_HDM_DECODER0_CTRL_COMMIT_ERROR, ctrl)) {
> -			ctrl &= ~CXL_HDM_DECODER0_CTRL_COMMIT;
> -			writel(ctrl, hdm + CXL_HDM_DECODER0_CTRL_OFFSET(id));
> -			return -EIO;
> -		}
> -		if (FIELD_GET(CXL_HDM_DECODER0_CTRL_COMMITTED, ctrl))
> -			return 0;
> -		fsleep(1000);
> -	}
> -
> -	return -ETIMEDOUT;
> -}
> -
> -static void setup_hw_decoder(void __iomem *hdm,
> -			     struct cxl_decoder_settings *settings)
> -{
> -	struct cxl_decoder_config *config = &settings->config;
> -	int id = config->id;
> -	u64 target_or_skip_reg_val;
> -	u64 base, size;
> -	u32 ctrl;
> -
> -	ctrl = readl(hdm + CXL_HDM_DECODER0_CTRL_OFFSET(id));
> -	cxld_set_interleave(config, &ctrl);
> -	cxld_set_type(config, &ctrl);
> -	base = config->hpa_range.start;
> -	size = range_len(&config->hpa_range);
> -	target_or_skip_reg_val = settings->target_or_skip_reg_val;
> -
> -	writel(upper_32_bits(base), hdm + CXL_HDM_DECODER0_BASE_HIGH_OFFSET(id));
> -	writel(lower_32_bits(base), hdm + CXL_HDM_DECODER0_BASE_LOW_OFFSET(id));
> -	writel(upper_32_bits(size), hdm + CXL_HDM_DECODER0_SIZE_HIGH_OFFSET(id));
> -	writel(lower_32_bits(size), hdm + CXL_HDM_DECODER0_SIZE_LOW_OFFSET(id));
> -	/* Target-list and endpoint-skip registers alias the same slot. */
> -	writel(upper_32_bits(target_or_skip_reg_val), hdm + CXL_HDM_DECODER0_TL_HIGH(id));
> -	writel(lower_32_bits(target_or_skip_reg_val), hdm + CXL_HDM_DECODER0_TL_LOW(id));
> -
> -	writel(ctrl, hdm + CXL_HDM_DECODER0_CTRL_OFFSET(id));
> -}
> -
> -void cxl_commit_start(void __iomem *hdm, struct cxl_decoder_settings *settings)
> -{
> -	lockdep_assert_held(&cxl_rwsem.dpa);
> -	setup_hw_decoder(hdm, settings);
> -}
> -
>  /*
>   * Endpoint skip and switch targets have different owners. Keep that state with
>   * its owning type and flatten it only into a transient register-programming
> diff --git a/drivers/cxl/core/resource.c b/drivers/cxl/core/resource.c
> new file mode 100644
> index 000000000000..ff027cb89e57
> --- /dev/null
> +++ b/drivers/cxl/core/resource.c
> @@ -0,0 +1,106 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/* Copyright (c) 2026 NVIDIA Corporation & Affiliates */
> +#include <linux/delay.h>
> +#include <linux/bug.h>
> +#include <linux/errno.h>
> +#include <linux/export.h>
> +#include <linux/kernel.h>
> +
> +#include "cxl.h"
> +#include "core.h"
> +
> +struct cxl_rwsem cxl_rwsem = {
> +	.region = __RWSEM_INITIALIZER(cxl_rwsem.region),
> +	.dpa = __RWSEM_INITIALIZER(cxl_rwsem.dpa),
> +};
> +EXPORT_SYMBOL_FOR_MODULES(cxl_rwsem, "cxl_core");
> +
> +static void cxld_set_interleave(struct cxl_decoder_config *config, u32 *ctrl)
> +{
> +	u16 eig;
> +	u8 eiw;
> +
> +	/*
> +	 * Input validation ensures these warns never fire, but otherwise
> +	 * suppress unititalized variable usage warnings.
> +	 */
> +	if (WARN_ONCE(ways_to_eiw(config->interleave_ways, &eiw),
> +		      "invalid interleave_ways: %d\n", config->interleave_ways))
> +		return;
> +	if (WARN_ONCE(granularity_to_eig(config->interleave_granularity, &eig),
> +		      "invalid interleave_granularity: %d\n",
> +		      config->interleave_granularity))
> +		return;
> +
> +	u32p_replace_bits(ctrl, eig, CXL_HDM_DECODER0_CTRL_IG_MASK);
> +	u32p_replace_bits(ctrl, eiw, CXL_HDM_DECODER0_CTRL_IW_MASK);
> +	*ctrl |= CXL_HDM_DECODER0_CTRL_COMMIT;
> +}
> +
> +static void cxld_set_type(struct cxl_decoder_config *config, u32 *ctrl)
> +{
> +	u32p_replace_bits(ctrl,
> +			  !!(config->target_type == CXL_DECODER_HOSTONLYMEM),
> +			  CXL_HDM_DECODER0_CTRL_HOSTONLY);
> +}
> +
> +/*
> + * Per CXL 2.0 8.2.5.12.20 Committing Decoder Programming, hardware must set
> + * committed or error within 10ms, but just be generous with 20ms to account for
> + * clock skew and other marginal behavior
> + */
> +#define COMMIT_TIMEOUT_MS 20
> +int cxld_await_commit(void __iomem *hdm, int id)
> +{
> +	u32 ctrl;
> +	int i;
> +
> +	for (i = 0; i < COMMIT_TIMEOUT_MS; i++) {
> +		ctrl = readl(hdm + CXL_HDM_DECODER0_CTRL_OFFSET(id));
> +		if (FIELD_GET(CXL_HDM_DECODER0_CTRL_COMMIT_ERROR, ctrl)) {
> +			ctrl &= ~CXL_HDM_DECODER0_CTRL_COMMIT;
> +			writel(ctrl, hdm + CXL_HDM_DECODER0_CTRL_OFFSET(id));
> +			return -EIO;
> +		}
> +		if (FIELD_GET(CXL_HDM_DECODER0_CTRL_COMMITTED, ctrl))
> +			return 0;
> +		fsleep(1000);
> +	}
> +
> +	return -ETIMEDOUT;
> +}
> +EXPORT_SYMBOL_FOR_MODULES(cxld_await_commit, "cxl_core");
> +
> +static void setup_hw_decoder(void __iomem *hdm,
> +			     struct cxl_decoder_settings *settings)
> +{
> +	struct cxl_decoder_config *config = &settings->config;
> +	int id = config->id;
> +	u64 target_or_skip_reg_val;
> +	u64 base, size;
> +	u32 ctrl;
> +
> +	ctrl = readl(hdm + CXL_HDM_DECODER0_CTRL_OFFSET(id));
> +	cxld_set_interleave(config, &ctrl);
> +	cxld_set_type(config, &ctrl);
> +	base = config->hpa_range.start;
> +	size = range_len(&config->hpa_range);
> +	target_or_skip_reg_val = settings->target_or_skip_reg_val;
> +
> +	writel(upper_32_bits(base), hdm + CXL_HDM_DECODER0_BASE_HIGH_OFFSET(id));
> +	writel(lower_32_bits(base), hdm + CXL_HDM_DECODER0_BASE_LOW_OFFSET(id));
> +	writel(upper_32_bits(size), hdm + CXL_HDM_DECODER0_SIZE_HIGH_OFFSET(id));
> +	writel(lower_32_bits(size), hdm + CXL_HDM_DECODER0_SIZE_LOW_OFFSET(id));
> +	/* Target-list and endpoint-skip registers alias the same slot. */
> +	writel(upper_32_bits(target_or_skip_reg_val), hdm + CXL_HDM_DECODER0_TL_HIGH(id));
> +	writel(lower_32_bits(target_or_skip_reg_val), hdm + CXL_HDM_DECODER0_TL_LOW(id));
> +
> +	writel(ctrl, hdm + CXL_HDM_DECODER0_CTRL_OFFSET(id));
> +}
> +
> +void cxl_commit_start(void __iomem *hdm, struct cxl_decoder_settings *settings)
> +{
> +	lockdep_assert_held(&cxl_rwsem.dpa);
> +	setup_hw_decoder(hdm, settings);
> +}
> +EXPORT_SYMBOL_FOR_MODULES(cxl_commit_start, "cxl_core");