Re: [PATCH v13 03/15] cxl: Move HDM decoder programming helpers

[Dave Jiang]

On 9/22/26 1:39 AM, Srirangan Madhavan wrote:
> Move the HDM decoder programming helpers and cxl_rwsem from hdm.c to
> resource.c for reuse by reset restoration. Keep their behavior unchanged
> and expose only the cross-object helpers within cxl_core.
> 
> Signed-off-by: Srirangan Madhavan <smadhavan@xxxxxxxxxx>

Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>

> ---
>  drivers/cxl/core/Makefile   |   1 +
>  drivers/cxl/core/core.h     |   4 ++
>  drivers/cxl/core/hdm.c      | 103 +--------------------------------
>  drivers/cxl/core/resource.c | 110 ++++++++++++++++++++++++++++++++++++
>  tools/testing/cxl/Kbuild    |   1 +
>  5 files changed, 117 insertions(+), 102 deletions(-)
>  create mode 100644 drivers/cxl/core/resource.c
> 
> diff --git a/drivers/cxl/core/Makefile b/drivers/cxl/core/Makefile
> index ce7213818d3c..57995777af0d 100644
> --- a/drivers/cxl/core/Makefile
> +++ b/drivers/cxl/core/Makefile
> @@ -6,6 +6,7 @@ ccflags-y += -I$(srctree)/drivers/cxl
>  CFLAGS_trace.o = -DTRACE_INCLUDE_PATH=. -I$(src)
>  
>  cxl_core-y := port.o
> +cxl_core-y += resource.o
>  cxl_core-y += pmem.o
>  cxl_core-y += regs.o
>  cxl_core-y += memdev.o
> diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
> index 983d7690c3a5..9c6d4b99f787 100644
> --- a/drivers/cxl/core/core.h
> +++ b/drivers/cxl/core/core.h
> @@ -139,6 +139,10 @@ struct cxl_rwsem {
>  
>  extern struct cxl_rwsem cxl_rwsem;
>  
> +int cxld_await_commit(void __iomem *hdm, int id);
> +void cxlsd_set_targets(struct cxl_switch_decoder *cxlsd, u64 *tgt);
> +void setup_hw_decoder(struct cxl_decoder *cxld, void __iomem *hdm);
> +
>  int cxl_memdev_init(void);
>  void cxl_memdev_exit(void);
>  void cxl_mbox_init(void);
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index 39fe283cbc74..008f04f0ca25 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;
> @@ -707,36 +702,7 @@ 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 *cxld, 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(cxld->interleave_ways, &eiw),
> -		      "invalid interleave_ways: %d\n", cxld->interleave_ways))
> -		return;
> -	if (WARN_ONCE(granularity_to_eig(cxld->interleave_granularity, &eig),
> -		      "invalid interleave_granularity: %d\n",
> -		      cxld->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 *cxld, u32 *ctrl)
> -{
> -	u32p_replace_bits(ctrl,
> -			  !!(cxld->target_type == CXL_DECODER_HOSTONLYMEM),
> -			  CXL_HDM_DECODER0_CTRL_HOSTONLY);
> -}
> -
> -static void cxlsd_set_targets(struct cxl_switch_decoder *cxlsd, u64 *tgt)
> +void cxlsd_set_targets(struct cxl_switch_decoder *cxlsd, u64 *tgt)
>  {
>  	struct cxl_dport **t = &cxlsd->target[0];
>  	int ways = cxlsd->cxld.interleave_ways;
> @@ -758,73 +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
> -static 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(struct cxl_decoder *cxld, void __iomem *hdm)
> -{
> -	int id = cxld->id;
> -	u64 base, size;
> -	u32 ctrl;
> -
> -	/* common decoder settings */
> -	ctrl = readl(hdm + CXL_HDM_DECODER0_CTRL_OFFSET(cxld->id));
> -	cxld_set_interleave(cxld, &ctrl);
> -	cxld_set_type(cxld, &ctrl);
> -	base = cxld->hpa_range.start;
> -	size = range_len(&cxld->hpa_range);
> -
> -	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));
> -
> -	if (is_switch_decoder(&cxld->dev)) {
> -		struct cxl_switch_decoder *cxlsd =
> -			to_cxl_switch_decoder(&cxld->dev);
> -		void __iomem *tl_hi = hdm + CXL_HDM_DECODER0_TL_HIGH(id);
> -		void __iomem *tl_lo = hdm + CXL_HDM_DECODER0_TL_LOW(id);
> -		u64 targets;
> -
> -		cxlsd_set_targets(cxlsd, &targets);
> -		writel(upper_32_bits(targets), tl_hi);
> -		writel(lower_32_bits(targets), tl_lo);
> -	} else {
> -		struct cxl_endpoint_decoder *cxled =
> -			to_cxl_endpoint_decoder(&cxld->dev);
> -		void __iomem *sk_hi = hdm + CXL_HDM_DECODER0_SKIP_HIGH(id);
> -		void __iomem *sk_lo = hdm + CXL_HDM_DECODER0_SKIP_LOW(id);
> -
> -		writel(upper_32_bits(cxled->skip), sk_hi);
> -		writel(lower_32_bits(cxled->skip), sk_lo);
> -	}
> -
> -	writel(ctrl, hdm + CXL_HDM_DECODER0_CTRL_OFFSET(id));
> -}
> -
>  static int cxl_decoder_commit(struct cxl_decoder *cxld)
>  {
>  	struct cxl_port *port = to_cxl_port(cxld->dev.parent);
> diff --git a/drivers/cxl/core/resource.c b/drivers/cxl/core/resource.c
> new file mode 100644
> index 000000000000..68d40f745acc
> --- /dev/null
> +++ b/drivers/cxl/core/resource.c
> @@ -0,0 +1,110 @@
> +// 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/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),
> +};
> +
> +static void cxld_set_interleave(struct cxl_decoder *cxld, 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(cxld->interleave_ways, &eiw),
> +		      "invalid interleave_ways: %d\n", cxld->interleave_ways))
> +		return;
> +	if (WARN_ONCE(granularity_to_eig(cxld->interleave_granularity, &eig),
> +		      "invalid interleave_granularity: %d\n",
> +		      cxld->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 *cxld, u32 *ctrl)
> +{
> +	u32p_replace_bits(ctrl,
> +			  !!(cxld->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;
> +}
> +
> +void setup_hw_decoder(struct cxl_decoder *cxld, void __iomem *hdm)
> +{
> +	int id = cxld->id;
> +	u64 base, size;
> +	u32 ctrl;
> +
> +	/* common decoder settings */
> +	ctrl = readl(hdm + CXL_HDM_DECODER0_CTRL_OFFSET(cxld->id));
> +	cxld_set_interleave(cxld, &ctrl);
> +	cxld_set_type(cxld, &ctrl);
> +	base = cxld->hpa_range.start;
> +	size = range_len(&cxld->hpa_range);
> +
> +	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));
> +
> +	if (is_switch_decoder(&cxld->dev)) {
> +		struct cxl_switch_decoder *cxlsd =
> +			to_cxl_switch_decoder(&cxld->dev);
> +		void __iomem *tl_hi = hdm + CXL_HDM_DECODER0_TL_HIGH(id);
> +		void __iomem *tl_lo = hdm + CXL_HDM_DECODER0_TL_LOW(id);
> +		u64 targets;
> +
> +		cxlsd_set_targets(cxlsd, &targets);
> +		writel(upper_32_bits(targets), tl_hi);
> +		writel(lower_32_bits(targets), tl_lo);
> +	} else {
> +		struct cxl_endpoint_decoder *cxled =
> +			to_cxl_endpoint_decoder(&cxld->dev);
> +		void __iomem *sk_hi = hdm + CXL_HDM_DECODER0_SKIP_HIGH(id);
> +		void __iomem *sk_lo = hdm + CXL_HDM_DECODER0_SKIP_LOW(id);
> +
> +		writel(upper_32_bits(cxled->skip), sk_hi);
> +		writel(lower_32_bits(cxled->skip), sk_lo);
> +	}
> +
> +	writel(ctrl, hdm + CXL_HDM_DECODER0_CTRL_OFFSET(id));
> +}
> diff --git a/tools/testing/cxl/Kbuild b/tools/testing/cxl/Kbuild
> index 2be1df80fcc9..6c09932587ce 100644
> --- a/tools/testing/cxl/Kbuild
> +++ b/tools/testing/cxl/Kbuild
> @@ -60,6 +60,7 @@ cxl_core-y += $(CXL_CORE_SRC)/memdev.o
>  cxl_core-y += $(CXL_CORE_SRC)/mbox.o
>  cxl_core-y += $(CXL_CORE_SRC)/pci.o
>  cxl_core-y += $(CXL_CORE_SRC)/hdm.o
> +cxl_core-y += $(CXL_CORE_SRC)/resource.o
>  cxl_core-y += $(CXL_CORE_SRC)/pmu.o
>  cxl_core-y += $(CXL_CORE_SRC)/cdat.o
>  cxl_core-$(CONFIG_TRACING) += $(CXL_CORE_SRC)/trace.o