[PATCH v10 0/6] Refactor capability search into common macros

[PATCH v10 0/6] Refactor capability search into common macros

[Hans Zhang]

Changes since v9:
- Resolved [v9 4/6] compilation error.
  The latest 6.15 rc1 merge __dw_pcie_find_vsec_capability, which uses 
  dw_pcie_find_next_ext_capability.
- The other patches have not been modified.

Changes since v8:
- Split patch.
- The patch commit message were modified.
- Other patches(4/6, 5/6, 6/6) are unchanged.

Changes since v7:
- Patch 2/5 and 3/5 compilation error resolved.
- Other patches are unchanged.

Changes since v6:
- Refactor capability search into common macros.
- Delete pci-host-helpers.c and MAINTAINERS.

Changes since v5:
- If you put the helpers in drivers/pci/pci.c, they unnecessarily enlarge
  the kernel's .text section even if it's known already at compile time
  that they're never going to be used (e.g. on x86).
- Move the API for find capabilitys to a new file called
  pci-host-helpers.c.
- Add new patch for MAINTAINERS.

Changes since v4:
- Resolved [v4 1/4] compilation warning.
- The patch subject and commit message were modified.

Changes since v3:
- Resolved [v3 1/4] compilation error.
- Other patches are not modified.

Changes since v2:
- Add and split into a series of patches.

Hans Zhang (6):
  PCI: Introduce generic bus config read helper function
  PCI: Clean up __pci_find_next_cap_ttl() readability
  PCI: Refactor capability search into common macros
  PCI: dwc: Use common PCI host bridge APIs for finding the capabilities
  PCI: cadence: Use common PCI host bridge APIs for finding the
    capabilities
  PCI: cadence: Use cdns_pcie_find_*capability to avoid hardcode.

 drivers/pci/access.c                          | 17 ++++
 .../pci/controller/cadence/pcie-cadence-ep.c  | 40 +++++----
 drivers/pci/controller/cadence/pcie-cadence.c | 28 ++++++
 drivers/pci/controller/cadence/pcie-cadence.h | 18 ++--
 drivers/pci/controller/dwc/pcie-designware.c  | 76 ++--------------
 drivers/pci/pci.c                             | 68 ++------------
 drivers/pci/pci.h                             | 88 +++++++++++++++++++
 include/uapi/linux/pci_regs.h                 |  2 +
 8 files changed, 189 insertions(+), 148 deletions(-)


base-commit: a24588245776dafc227243a01bfbeb8a59bafba9
-- 
2.25.1

[PATCH v10 1/6] PCI: Introduce generic bus config read helper function

[Hans Zhang]

The primary PCI config space accessors are tied to the size of the read
(byte/word/dword). Upcoming refactoring of PCI capability discovery logic
requires passing a config accessor function that must be able to perform
read with different sizes.

Add any size config space read accessor pci_bus_read_config() to allow
giving it as the config space accessor to the upcoming PCI capability
discovery macro.

Reconstructs the PCI function discovery logic to prepare for unified
configuration of access modes. No function changes are intended.

Signed-off-by: Hans Zhang <18255117159@163.com>
---
Changes since v9:
- None

Changes since v8:
- The new split is patch 1/6.
- The patch commit message were modified.
---
 drivers/pci/access.c | 17 +++++++++++++++++
 drivers/pci/pci.h    |  2 ++
 2 files changed, 19 insertions(+)

diff --git a/drivers/pci/access.c b/drivers/pci/access.c
index b123da16b63b..603332658ab3 100644
--- a/drivers/pci/access.c
+++ b/drivers/pci/access.c
@@ -85,6 +85,23 @@ EXPORT_SYMBOL(pci_bus_write_config_byte);
 EXPORT_SYMBOL(pci_bus_write_config_word);
 EXPORT_SYMBOL(pci_bus_write_config_dword);
 
+int pci_bus_read_config(void *priv, unsigned int devfn, int where, u32 size,
+			u32 *val)
+{
+	struct pci_bus *bus = priv;
+	int ret;
+
+	if (size == 1)
+		ret = pci_bus_read_config_byte(bus, devfn, where, (u8 *)val);
+	else if (size == 2)
+		ret = pci_bus_read_config_word(bus, devfn, where, (u16 *)val);
+	else
+		ret = pci_bus_read_config_dword(bus, devfn, where, val);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pci_bus_read_config);
+
 int pci_generic_config_read(struct pci_bus *bus, unsigned int devfn,
 			    int where, int size, u32 *val)
 {
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index b81e99cd4b62..5e1477d6e254 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -88,6 +88,8 @@ extern bool pci_early_dump;
 bool pcie_cap_has_lnkctl(const struct pci_dev *dev);
 bool pcie_cap_has_lnkctl2(const struct pci_dev *dev);
 bool pcie_cap_has_rtctl(const struct pci_dev *dev);
+int pci_bus_read_config(void *priv, unsigned int devfn, int where, u32 size,
+			u32 *val);
 
 /* Functions internal to the PCI core code */
 
-- 
2.25.1

[PATCH v10 2/6] PCI: Clean up __pci_find_next_cap_ttl() readability

[Hans Zhang]

Refactor the __pci_find_next_cap_ttl() to improve code clarity:
- Replace magic number 0x40 with PCI_STD_HEADER_SIZEOF.
- Use ALIGN_DOWN() for position alignment instead of manual bitmask.
- Extract PCI capability fields via FIELD_GET() with standardized masks.
- Add necessary headers (linux/align.h, uapi/linux/pci_regs.h).

The changes are purely non-functional cleanups, ensuring behavior remains
identical to the original implementation.

Signed-off-by: Hans Zhang <18255117159@163.com>
---
Changes since v9:
- None

Changes since v8:
- Split into patch 1/6, patch 2/6.
- The
 drivers/pci/pci.c             | 10 ++++++----
 include/uapi/linux/pci_regs.h |  2 ++
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 4d7c9f64ea24..1c29e8f20cb5 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -9,6 +9,7 @@
  */
 
 #include <linux/acpi.h>
+#include <linux/align.h>
 #include <linux/kernel.h>
 #include <linux/delay.h>
 #include <linux/dmi.h>
@@ -30,6 +31,7 @@
 #include <asm/dma.h>
 #include <linux/aer.h>
 #include <linux/bitfield.h>
+#include <uapi/linux/pci_regs.h>
 #include "pci.h"
 
 DEFINE_MUTEX(pci_slot_mutex);
@@ -432,17 +434,17 @@ static u8 __pci_find_next_cap_ttl(struct pci_bus *bus, unsigned int devfn,
 	pci_bus_read_config_byte(bus, devfn, pos, &pos);
 
 	while ((*ttl)--) {
-		if (pos < 0x40)
+		if (pos < PCI_STD_HEADER_SIZEOF)
 			break;
-		pos &= ~3;
+		pos = ALIGN_DOWN(pos, 4);
 		pci_bus_read_config_word(bus, devfn, pos, &ent);
 
-		id = ent & 0xff;
+		id = FIELD_GET(PCI_CAP_ID_MASK, ent);
 		if (id == 0xff)
 			break;
 		if (id == cap)
 			return pos;
-		pos = (ent >> 8);
+		pos = FIELD_GET(PCI_CAP_LIST_NEXT_MASK, ent);
 	}
 	return 0;
 }
diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
index ba326710f9c8..b59179e1210a 100644
--- a/include/uapi/linux/pci_regs.h
+++ b/include/uapi/linux/pci_regs.h
@@ -206,6 +206,8 @@
 /* 0x48-0x7f reserved */
 
 /* Capability lists */
+#define PCI_CAP_ID_MASK		0x00ff
+#define PCI_CAP_LIST_NEXT_MASK	0xff00
 
 #define PCI_CAP_LIST_ID		0	/* Capability ID */
 #define  PCI_CAP_ID_PM		0x01	/* Power Management */
-- 
2.25.1

Re: [PATCH v10 2/6] PCI: Clean up __pci_find_next_cap_ttl() readability

[Ilpo Järvinen]

On Tue, 29 Apr 2025, Hans Zhang wrote:

> Refactor the __pci_find_next_cap_ttl() to improve code clarity:
> - Replace magic number 0x40 with PCI_STD_HEADER_SIZEOF.
> - Use ALIGN_DOWN() for position alignment instead of manual bitmask.
> - Extract PCI capability fields via FIELD_GET() with standardized masks.
> - Add necessary headers (linux/align.h, uapi/linux/pci_regs.h).
> 
> The changes are purely non-functional cleanups, ensuring behavior remains
> identical to the original implementation.
> 
> Signed-off-by: Hans Zhang <18255117159@163.com>
> ---
> Changes since v9:
> - None
> 
> Changes since v8:
> - Split into patch 1/6, patch 2/6.
> - The
>  drivers/pci/pci.c             | 10 ++++++----
>  include/uapi/linux/pci_regs.h |  2 ++
>  2 files changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 4d7c9f64ea24..1c29e8f20cb5 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -9,6 +9,7 @@
>   */
>  
>  #include <linux/acpi.h>
> +#include <linux/align.h>
>  #include <linux/kernel.h>
>  #include <linux/delay.h>
>  #include <linux/dmi.h>
> @@ -30,6 +31,7 @@
>  #include <asm/dma.h>
>  #include <linux/aer.h>
>  #include <linux/bitfield.h>
> +#include <uapi/linux/pci_regs.h>

linux/pci.h will pull this in through <uapi/linux/pci.h> so you don't need 
to add it (basically anywhere).

>  #include "pci.h"
>  
>  DEFINE_MUTEX(pci_slot_mutex);
> @@ -432,17 +434,17 @@ static u8 __pci_find_next_cap_ttl(struct pci_bus *bus, unsigned int devfn,
>  	pci_bus_read_config_byte(bus, devfn, pos, &pos);
>  
>  	while ((*ttl)--) {
> -		if (pos < 0x40)
> +		if (pos < PCI_STD_HEADER_SIZEOF)
>  			break;
> -		pos &= ~3;
> +		pos = ALIGN_DOWN(pos, 4);
>  		pci_bus_read_config_word(bus, devfn, pos, &ent);
>  
> -		id = ent & 0xff;
> +		id = FIELD_GET(PCI_CAP_ID_MASK, ent);
>  		if (id == 0xff)
>  			break;
>  		if (id == cap)
>  			return pos;
> -		pos = (ent >> 8);
> +		pos = FIELD_GET(PCI_CAP_LIST_NEXT_MASK, ent);
>  	}
>  	return 0;
>  }
> diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
> index ba326710f9c8..b59179e1210a 100644
> --- a/include/uapi/linux/pci_regs.h
> +++ b/include/uapi/linux/pci_regs.h
> @@ -206,6 +206,8 @@
>  /* 0x48-0x7f reserved */
>  
>  /* Capability lists */
> +#define PCI_CAP_ID_MASK		0x00ff
> +#define PCI_CAP_LIST_NEXT_MASK	0xff00

Consider adding a comment after the value as is done for most  defines in 
this file.

>  
>  #define PCI_CAP_LIST_ID		0	/* Capability ID */
>  #define  PCI_CAP_ID_PM		0x01	/* Power Management */
> 

-- 
 i.

Re: [PATCH v10 2/6] PCI: Clean up __pci_find_next_cap_ttl() readability

[Hans Zhang]

On 2025/4/29 23:17, Ilpo Järvinen wrote:
> On Tue, 29 Apr 2025, Hans Zhang wrote:
> 
>> Refactor the __pci_find_next_cap_ttl() to improve code clarity:
>> - Replace magic number 0x40 with PCI_STD_HEADER_SIZEOF.
>> - Use ALIGN_DOWN() for position alignment instead of manual bitmask.
>> - Extract PCI capability fields via FIELD_GET() with standardized masks.
>> - Add necessary headers (linux/align.h, uapi/linux/pci_regs.h).
>>
>> The changes are purely non-functional cleanups, ensuring behavior remains
>> identical to the original implementation.
>>
>> Signed-off-by: Hans Zhang <18255117159@163.com>
>> ---
>> Changes since v9:
>> - None
>>
>> Changes since v8:
>> - Split into patch 1/6, patch 2/6.
>> - The
>>   drivers/pci/pci.c             | 10 ++++++----
>>   include/uapi/linux/pci_regs.h |  2 ++
>>   2 files changed, 8 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
>> index 4d7c9f64ea24..1c29e8f20cb5 100644
>> --- a/drivers/pci/pci.c
>> +++ b/drivers/pci/pci.c
>> @@ -9,6 +9,7 @@
>>    */
>>   
>>   #include <linux/acpi.h>
>> +#include <linux/align.h>
>>   #include <linux/kernel.h>
>>   #include <linux/delay.h>
>>   #include <linux/dmi.h>
>> @@ -30,6 +31,7 @@
>>   #include <asm/dma.h>
>>   #include <linux/aer.h>
>>   #include <linux/bitfield.h>
>> +#include <uapi/linux/pci_regs.h>
> 
> linux/pci.h will pull this in through <uapi/linux/pci.h> so you don't need
> to add it (basically anywhere).
> 
>>   #include "pci.h"
>>   
>>   DEFINE_MUTEX(pci_slot_mutex);
>> @@ -432,17 +434,17 @@ static u8 __pci_find_next_cap_ttl(struct pci_bus *bus, unsigned int devfn,
>>   	pci_bus_read_config_byte(bus, devfn, pos, &pos);
>>   
>>   	while ((*ttl)--) {
>> -		if (pos < 0x40)
>> +		if (pos < PCI_STD_HEADER_SIZEOF)
>>   			break;
>> -		pos &= ~3;
>> +		pos = ALIGN_DOWN(pos, 4);
>>   		pci_bus_read_config_word(bus, devfn, pos, &ent);
>>   
>> -		id = ent & 0xff;
>> +		id = FIELD_GET(PCI_CAP_ID_MASK, ent);
>>   		if (id == 0xff)
>>   			break;
>>   		if (id == cap)
>>   			return pos;
>> -		pos = (ent >> 8);
>> +		pos = FIELD_GET(PCI_CAP_LIST_NEXT_MASK, ent);
>>   	}
>>   	return 0;
>>   }
>> diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
>> index ba326710f9c8..b59179e1210a 100644
>> --- a/include/uapi/linux/pci_regs.h
>> +++ b/include/uapi/linux/pci_regs.h
>> @@ -206,6 +206,8 @@
>>   /* 0x48-0x7f reserved */
>>   
>>   /* Capability lists */
>> +#define PCI_CAP_ID_MASK		0x00ff
>> +#define PCI_CAP_LIST_NEXT_MASK	0xff00
> 
> Consider adding a comment after the value as is done for most  defines in
> this file.

Dear Ilpo,

Thank you very much for your reply. Will add.

Best regards,
Hans

> 
>>   
>>   #define PCI_CAP_LIST_ID		0	/* Capability ID */
>>   #define  PCI_CAP_ID_PM		0x01	/* Power Management */
>>
> 

Re: [PATCH v10 2/6] PCI: Clean up __pci_find_next_cap_ttl() readability

[Hans Zhang]

On 2025/4/29 23:17, Ilpo Järvinen wrote:
>>   #include <linux/acpi.h>
>> +#include <linux/align.h>
>>   #include <linux/kernel.h>
>>   #include <linux/delay.h>
>>   #include <linux/dmi.h>
>> @@ -30,6 +31,7 @@
>>   #include <asm/dma.h>
>>   #include <linux/aer.h>
>>   #include <linux/bitfield.h>
>> +#include <uapi/linux/pci_regs.h>
> 
> linux/pci.h will pull this in through <uapi/linux/pci.h> so you don't need
> to add it (basically anywhere).

Dear Ilpo,

Will delete.

Best regards,
Hans

[PATCH v10 3/6] PCI: Refactor capability search into common macros

[Hans Zhang]

The PCI Capability search functionality is duplicated across the PCI core
and several controller drivers. The core's current implementation requires
fully initialized PCI device and bus structures, which prevents controller
drivers from using it during early initialization phases before these
structures are available.

Move the Capability search logic into a header-based macro that accepts a
config space accessor function as an argument. This enables controller
drivers to perform Capability discovery using their early access
mechanisms prior to full device initialization while sharing the
Capability search code.

Convert the existing PCI core Capability search implementation to use this
new macro.

The macros now implement, parameterized by the config access method. The
PCI core functions are converted to utilize these macros with the standard
pci_bus_read_config accessors. Controller drivers can later use the same
macros with their early access mechanisms while maintaining the existing
protection against infinite loops through preserved TTL checks.

The ttl parameter was originally an additional safeguard to prevent
infinite loops in corrupted config space.  However, the
PCI_FIND_NEXT_CAP_TTL macro already enforces a TTL limit internally.
Removing redundant ttl handling simplifies the interface while maintaining
the safety guarantee. This aligns with the macro's design intent of
encapsulating TTL management.

Signed-off-by: Hans Zhang <18255117159@163.com>
---
Changes since v9:
- None

Changes since v8:
- The patch commit message were modified.
---
 drivers/pci/pci.c | 70 +++++---------------------------------
 drivers/pci/pci.h | 86 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 95 insertions(+), 61 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 1c29e8f20cb5..8a1f47e8f5cc 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -9,7 +9,6 @@
  */
 
 #include <linux/acpi.h>
-#include <linux/align.h>
 #include <linux/kernel.h>
 #include <linux/delay.h>
 #include <linux/dmi.h>
@@ -31,7 +30,6 @@
 #include <asm/dma.h>
 #include <linux/aer.h>
 #include <linux/bitfield.h>
-#include <uapi/linux/pci_regs.h>
 #include "pci.h"
 
 DEFINE_MUTEX(pci_slot_mutex);
@@ -426,35 +424,16 @@ static int pci_dev_str_match(struct pci_dev *dev, const char *p,
 }
 
 static u8 __pci_find_next_cap_ttl(struct pci_bus *bus, unsigned int devfn,
-				  u8 pos, int cap, int *ttl)
+				  u8 pos, int cap)
 {
-	u8 id;
-	u16 ent;
-
-	pci_bus_read_config_byte(bus, devfn, pos, &pos);
-
-	while ((*ttl)--) {
-		if (pos < PCI_STD_HEADER_SIZEOF)
-			break;
-		pos = ALIGN_DOWN(pos, 4);
-		pci_bus_read_config_word(bus, devfn, pos, &ent);
-
-		id = FIELD_GET(PCI_CAP_ID_MASK, ent);
-		if (id == 0xff)
-			break;
-		if (id == cap)
-			return pos;
-		pos = FIELD_GET(PCI_CAP_LIST_NEXT_MASK, ent);
-	}
-	return 0;
+	return PCI_FIND_NEXT_CAP_TTL(pci_bus_read_config, pos, cap, bus,
+				     devfn);
 }
 
 static u8 __pci_find_next_cap(struct pci_bus *bus, unsigned int devfn,
 			      u8 pos, int cap)
 {
-	int ttl = PCI_FIND_CAP_TTL;
-
-	return __pci_find_next_cap_ttl(bus, devfn, pos, cap, &ttl);
+	return __pci_find_next_cap_ttl(bus, devfn, pos, cap);
 }
 
 u8 pci_find_next_capability(struct pci_dev *dev, u8 pos, int cap)
@@ -555,42 +534,11 @@ EXPORT_SYMBOL(pci_bus_find_capability);
  */
 u16 pci_find_next_ext_capability(struct pci_dev *dev, u16 start, int cap)
 {
-	u32 header;
-	int ttl;
-	u16 pos = PCI_CFG_SPACE_SIZE;
-
-	/* minimum 8 bytes per capability */
-	ttl = (PCI_CFG_SPACE_EXP_SIZE - PCI_CFG_SPACE_SIZE) / 8;
-
 	if (dev->cfg_size <= PCI_CFG_SPACE_SIZE)
 		return 0;
 
-	if (start)
-		pos = start;
-
-	if (pci_read_config_dword(dev, pos, &header) != PCIBIOS_SUCCESSFUL)
-		return 0;
-
-	/*
-	 * If we have no capabilities, this is indicated by cap ID,
-	 * cap version and next pointer all being 0.
-	 */
-	if (header == 0)
-		return 0;
-
-	while (ttl-- > 0) {
-		if (PCI_EXT_CAP_ID(header) == cap && pos != start)
-			return pos;
-
-		pos = PCI_EXT_CAP_NEXT(header);
-		if (pos < PCI_CFG_SPACE_SIZE)
-			break;
-
-		if (pci_read_config_dword(dev, pos, &header) != PCIBIOS_SUCCESSFUL)
-			break;
-	}
-
-	return 0;
+	return PCI_FIND_NEXT_EXT_CAPABILITY(pci_bus_read_config, start, cap,
+					    dev->bus, dev->devfn);
 }
 EXPORT_SYMBOL_GPL(pci_find_next_ext_capability);
 
@@ -650,7 +598,7 @@ EXPORT_SYMBOL_GPL(pci_get_dsn);
 
 static u8 __pci_find_next_ht_cap(struct pci_dev *dev, u8 pos, int ht_cap)
 {
-	int rc, ttl = PCI_FIND_CAP_TTL;
+	int rc;
 	u8 cap, mask;
 
 	if (ht_cap == HT_CAPTYPE_SLAVE || ht_cap == HT_CAPTYPE_HOST)
@@ -659,7 +607,7 @@ static u8 __pci_find_next_ht_cap(struct pci_dev *dev, u8 pos, int ht_cap)
 		mask = HT_5BIT_CAP_MASK;
 
 	pos = __pci_find_next_cap_ttl(dev->bus, dev->devfn, pos,
-				      PCI_CAP_ID_HT, &ttl);
+				      PCI_CAP_ID_HT);
 	while (pos) {
 		rc = pci_read_config_byte(dev, pos + 3, &cap);
 		if (rc != PCIBIOS_SUCCESSFUL)
@@ -670,7 +618,7 @@ static u8 __pci_find_next_ht_cap(struct pci_dev *dev, u8 pos, int ht_cap)
 
 		pos = __pci_find_next_cap_ttl(dev->bus, dev->devfn,
 					      pos + PCI_CAP_LIST_NEXT,
-					      PCI_CAP_ID_HT, &ttl);
+					      PCI_CAP_ID_HT);
 	}
 
 	return 0;
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 5e1477d6e254..79cd6402ba8d 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -2,7 +2,9 @@
 #ifndef DRIVERS_PCI_H
 #define DRIVERS_PCI_H
 
+#include <linux/align.h>
 #include <linux/pci.h>
+#include <uapi/linux/pci_regs.h>
 
 struct pcie_tlp_log;
 
@@ -91,6 +93,90 @@ bool pcie_cap_has_rtctl(const struct pci_dev *dev);
 int pci_bus_read_config(void *priv, unsigned int devfn, int where, u32 size,
 			u32 *val);
 
+/* Standard Capability finder */
+/**
+ * PCI_FIND_NEXT_CAP_TTL - Find a PCI standard capability
+ * @read_cfg: Function pointer for reading PCI config space
+ * @start: Starting position to begin search
+ * @cap: Capability ID to find
+ * @args: Arguments to pass to read_cfg function
+ *
+ * Iterates through the capability list in PCI config space to find
+ * the specified capability. Implements TTL (time-to-live) protection
+ * against infinite loops.
+ *
+ * Returns: Position of the capability if found, 0 otherwise.
+ */
+#define PCI_FIND_NEXT_CAP_TTL(read_cfg, start, cap, args...)		\
+({									\
+	int __ttl = PCI_FIND_CAP_TTL;					\
+	u8 __id, __found_pos = 0;					\
+	u8 __pos = (start);						\
+	u16 __ent;							\
+									\
+	read_cfg(args, __pos, 1, (u32 *)&__pos);			\
+									\
+	while (__ttl--) {						\
+		if (__pos < PCI_STD_HEADER_SIZEOF)			\
+			break;						\
+									\
+		__pos = ALIGN_DOWN(__pos, 4);				\
+		read_cfg(args, __pos, 2, (u32 *)&__ent);		\
+									\
+		__id = FIELD_GET(PCI_CAP_ID_MASK, __ent);		\
+		if (__id == 0xff)					\
+			break;						\
+									\
+		if (__id == (cap)) {					\
+			__found_pos = __pos;				\
+			break;						\
+		}							\
+									\
+		__pos = FIELD_GET(PCI_CAP_LIST_NEXT_MASK, __ent);	\
+	}								\
+	__found_pos;							\
+})
+
+/* Extended Capability finder */
+/**
+ * PCI_FIND_NEXT_EXT_CAPABILITY - Find a PCI extended capability
+ * @read_cfg: Function pointer for reading PCI config space
+ * @start: Starting position to begin search (0 for initial search)
+ * @cap: Extended capability ID to find
+ * @args: Arguments to pass to read_cfg function
+ *
+ * Searches the extended capability space in PCI config registers
+ * for the specified capability. Implements TTL protection against
+ * infinite loops using a calculated maximum search count.
+ *
+ * Returns: Position of the capability if found, 0 otherwise.
+ */
+#define PCI_FIND_NEXT_EXT_CAPABILITY(read_cfg, start, cap, args...)		\
+({										\
+	u16 __pos = (start) ?: PCI_CFG_SPACE_SIZE;				\
+	u16 __found_pos = 0;							\
+	int __ttl, __ret;							\
+	u32 __header;								\
+										\
+	__ttl = (PCI_CFG_SPACE_EXP_SIZE - PCI_CFG_SPACE_SIZE) / 8;		\
+	while (__ttl-- > 0 && __pos >= PCI_CFG_SPACE_SIZE) {			\
+		__ret = read_cfg(args, __pos, 4, &__header);			\
+		if (__ret != PCIBIOS_SUCCESSFUL)				\
+			break;							\
+										\
+		if (__header == 0)						\
+			break;							\
+										\
+		if (PCI_EXT_CAP_ID(__header) == (cap) && __pos != start) {	\
+			__found_pos = __pos;					\
+			break;							\
+		}								\
+										\
+		__pos = PCI_EXT_CAP_NEXT(__header);				\
+	}									\
+	__found_pos;								\
+})
+
 /* Functions internal to the PCI core code */
 
 #ifdef CONFIG_DMI
-- 
2.25.1

Re: [PATCH v10 3/6] PCI: Refactor capability search into common macros

[Ilpo Järvinen]

On Tue, 29 Apr 2025, Hans Zhang wrote:

> The PCI Capability search functionality is duplicated across the PCI core
> and several controller drivers. The core's current implementation requires
> fully initialized PCI device and bus structures, which prevents controller
> drivers from using it during early initialization phases before these
> structures are available.
> 
> Move the Capability search logic into a header-based macro that accepts a
> config space accessor function as an argument. This enables controller
> drivers to perform Capability discovery using their early access
> mechanisms prior to full device initialization while sharing the
> Capability search code.
> 
> Convert the existing PCI core Capability search implementation to use this
> new macro.
> 
> The macros now implement, parameterized by the config access method. The

This sentence is incomplete (and sounds pretty much duplicated 
information anyway).

> PCI core functions are converted to utilize these macros with the standard
> pci_bus_read_config accessors.

This info is duplicated.

> Controller drivers can later use the same
> macros with their early access mechanisms while maintaining the existing
> protection against infinite loops through preserved TTL checks.
> 
> The ttl parameter was originally an additional safeguard to prevent
> infinite loops in corrupted config space.  However, the
> PCI_FIND_NEXT_CAP_TTL macro already enforces a TTL limit internally.
> Removing redundant ttl handling simplifies the interface while maintaining
> the safety guarantee. This aligns with the macro's design intent of
> encapsulating TTL management.
> 
> Signed-off-by: Hans Zhang <18255117159@163.com>
> ---
> Changes since v9:
> - None
> 
> Changes since v8:
> - The patch commit message were modified.
> ---
>  drivers/pci/pci.c | 70 +++++---------------------------------
>  drivers/pci/pci.h | 86 +++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 95 insertions(+), 61 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 1c29e8f20cb5..8a1f47e8f5cc 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -9,7 +9,6 @@
>   */
>  
>  #include <linux/acpi.h>
> -#include <linux/align.h>
>  #include <linux/kernel.h>
>  #include <linux/delay.h>
>  #include <linux/dmi.h>
> @@ -31,7 +30,6 @@
>  #include <asm/dma.h>
>  #include <linux/aer.h>
>  #include <linux/bitfield.h>
> -#include <uapi/linux/pci_regs.h>
>  #include "pci.h"
>  
>  DEFINE_MUTEX(pci_slot_mutex);
> @@ -426,35 +424,16 @@ static int pci_dev_str_match(struct pci_dev *dev, const char *p,
>  }
>  
>  static u8 __pci_find_next_cap_ttl(struct pci_bus *bus, unsigned int devfn,
> -				  u8 pos, int cap, int *ttl)
> +				  u8 pos, int cap)
>  {
> -	u8 id;
> -	u16 ent;
> -
> -	pci_bus_read_config_byte(bus, devfn, pos, &pos);
> -
> -	while ((*ttl)--) {
> -		if (pos < PCI_STD_HEADER_SIZEOF)
> -			break;
> -		pos = ALIGN_DOWN(pos, 4);
> -		pci_bus_read_config_word(bus, devfn, pos, &ent);
> -
> -		id = FIELD_GET(PCI_CAP_ID_MASK, ent);
> -		if (id == 0xff)
> -			break;
> -		if (id == cap)
> -			return pos;
> -		pos = FIELD_GET(PCI_CAP_LIST_NEXT_MASK, ent);
> -	}
> -	return 0;
> +	return PCI_FIND_NEXT_CAP_TTL(pci_bus_read_config, pos, cap, bus,
> +				     devfn);
>  }
>  
>  static u8 __pci_find_next_cap(struct pci_bus *bus, unsigned int devfn,
>  			      u8 pos, int cap)
>  {
> -	int ttl = PCI_FIND_CAP_TTL;
> -
> -	return __pci_find_next_cap_ttl(bus, devfn, pos, cap, &ttl);
> +	return __pci_find_next_cap_ttl(bus, devfn, pos, cap);
>  }
>  
>  u8 pci_find_next_capability(struct pci_dev *dev, u8 pos, int cap)
> @@ -555,42 +534,11 @@ EXPORT_SYMBOL(pci_bus_find_capability);
>   */
>  u16 pci_find_next_ext_capability(struct pci_dev *dev, u16 start, int cap)
>  {
> -	u32 header;
> -	int ttl;
> -	u16 pos = PCI_CFG_SPACE_SIZE;
> -
> -	/* minimum 8 bytes per capability */
> -	ttl = (PCI_CFG_SPACE_EXP_SIZE - PCI_CFG_SPACE_SIZE) / 8;
> -
>  	if (dev->cfg_size <= PCI_CFG_SPACE_SIZE)
>  		return 0;
>  
> -	if (start)
> -		pos = start;
> -
> -	if (pci_read_config_dword(dev, pos, &header) != PCIBIOS_SUCCESSFUL)
> -		return 0;
> -
> -	/*
> -	 * If we have no capabilities, this is indicated by cap ID,
> -	 * cap version and next pointer all being 0.
> -	 */
> -	if (header == 0)
> -		return 0;
> -
> -	while (ttl-- > 0) {
> -		if (PCI_EXT_CAP_ID(header) == cap && pos != start)
> -			return pos;
> -
> -		pos = PCI_EXT_CAP_NEXT(header);
> -		if (pos < PCI_CFG_SPACE_SIZE)
> -			break;
> -
> -		if (pci_read_config_dword(dev, pos, &header) != PCIBIOS_SUCCESSFUL)
> -			break;
> -	}
> -
> -	return 0;
> +	return PCI_FIND_NEXT_EXT_CAPABILITY(pci_bus_read_config, start, cap,
> +					    dev->bus, dev->devfn);
>  }
>  EXPORT_SYMBOL_GPL(pci_find_next_ext_capability);
>  
> @@ -650,7 +598,7 @@ EXPORT_SYMBOL_GPL(pci_get_dsn);
>  
>  static u8 __pci_find_next_ht_cap(struct pci_dev *dev, u8 pos, int ht_cap)
>  {
> -	int rc, ttl = PCI_FIND_CAP_TTL;
> +	int rc;
>  	u8 cap, mask;
>  
>  	if (ht_cap == HT_CAPTYPE_SLAVE || ht_cap == HT_CAPTYPE_HOST)
> @@ -659,7 +607,7 @@ static u8 __pci_find_next_ht_cap(struct pci_dev *dev, u8 pos, int ht_cap)
>  		mask = HT_5BIT_CAP_MASK;
>  
>  	pos = __pci_find_next_cap_ttl(dev->bus, dev->devfn, pos,
> -				      PCI_CAP_ID_HT, &ttl);
> +				      PCI_CAP_ID_HT);
>  	while (pos) {
>  		rc = pci_read_config_byte(dev, pos + 3, &cap);
>  		if (rc != PCIBIOS_SUCCESSFUL)
> @@ -670,7 +618,7 @@ static u8 __pci_find_next_ht_cap(struct pci_dev *dev, u8 pos, int ht_cap)
>  
>  		pos = __pci_find_next_cap_ttl(dev->bus, dev->devfn,
>  					      pos + PCI_CAP_LIST_NEXT,
> -					      PCI_CAP_ID_HT, &ttl);
> +					      PCI_CAP_ID_HT);
>  	}
>  
>  	return 0;
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index 5e1477d6e254..79cd6402ba8d 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -2,7 +2,9 @@
>  #ifndef DRIVERS_PCI_H
>  #define DRIVERS_PCI_H
>  
> +#include <linux/align.h>
>  #include <linux/pci.h>
> +#include <uapi/linux/pci_regs.h>
>  
>  struct pcie_tlp_log;
>  
> @@ -91,6 +93,90 @@ bool pcie_cap_has_rtctl(const struct pci_dev *dev);
>  int pci_bus_read_config(void *priv, unsigned int devfn, int where, u32 size,
>  			u32 *val);
>  
> +/* Standard Capability finder */
> +/**
> + * PCI_FIND_NEXT_CAP_TTL - Find a PCI standard capability
> + * @read_cfg: Function pointer for reading PCI config space
> + * @start: Starting position to begin search
> + * @cap: Capability ID to find
> + * @args: Arguments to pass to read_cfg function
> + *
> + * Iterates through the capability list in PCI config space to find
> + * the specified capability. Implements TTL (time-to-live) protection
> + * against infinite loops.
> + *
> + * Returns: Position of the capability if found, 0 otherwise.
> + */
> +#define PCI_FIND_NEXT_CAP_TTL(read_cfg, start, cap, args...)		\
> +({									\
> +	int __ttl = PCI_FIND_CAP_TTL;					\
> +	u8 __id, __found_pos = 0;					\
> +	u8 __pos = (start);						\
> +	u16 __ent;							\
> +									\
> +	read_cfg(args, __pos, 1, (u32 *)&__pos);			\
> +									\
> +	while (__ttl--) {						\
> +		if (__pos < PCI_STD_HEADER_SIZEOF)			\
> +			break;						\
> +									\
> +		__pos = ALIGN_DOWN(__pos, 4);				\
> +		read_cfg(args, __pos, 2, (u32 *)&__ent);		\

You seem to have dropped the return value checks?

> +									\
> +		__id = FIELD_GET(PCI_CAP_ID_MASK, __ent);		\
> +		if (__id == 0xff)					\
> +			break;						\
> +									\
> +		if (__id == (cap)) {					\
> +			__found_pos = __pos;				\
> +			break;						\
> +		}							\
> +									\
> +		__pos = FIELD_GET(PCI_CAP_LIST_NEXT_MASK, __ent);	\
> +	}								\
> +	__found_pos;							\
> +})
> +
> +/* Extended Capability finder */
> +/**
> + * PCI_FIND_NEXT_EXT_CAPABILITY - Find a PCI extended capability
> + * @read_cfg: Function pointer for reading PCI config space
> + * @start: Starting position to begin search (0 for initial search)
> + * @cap: Extended capability ID to find
> + * @args: Arguments to pass to read_cfg function
> + *
> + * Searches the extended capability space in PCI config registers
> + * for the specified capability. Implements TTL protection against
> + * infinite loops using a calculated maximum search count.
> + *
> + * Returns: Position of the capability if found, 0 otherwise.
> + */
> +#define PCI_FIND_NEXT_EXT_CAPABILITY(read_cfg, start, cap, args...)		\
> +({										\
> +	u16 __pos = (start) ?: PCI_CFG_SPACE_SIZE;				\
> +	u16 __found_pos = 0;							\
> +	int __ttl, __ret;							\
> +	u32 __header;								\
> +										\
> +	__ttl = (PCI_CFG_SPACE_EXP_SIZE - PCI_CFG_SPACE_SIZE) / 8;		\
> +	while (__ttl-- > 0 && __pos >= PCI_CFG_SPACE_SIZE) {			\
> +		__ret = read_cfg(args, __pos, 4, &__header);			\
> +		if (__ret != PCIBIOS_SUCCESSFUL)				\
> +			break;							\
> +										\
> +		if (__header == 0)						\
> +			break;							\
> +										\
> +		if (PCI_EXT_CAP_ID(__header) == (cap) && __pos != start) {	\
> +			__found_pos = __pos;					\
> +			break;							\
> +		}								\
> +										\
> +		__pos = PCI_EXT_CAP_NEXT(__header);				\
> +	}									\
> +	__found_pos;								\
> +})
> +
>  /* Functions internal to the PCI core code */
>  
>  #ifdef CONFIG_DMI
> 

-- 
 i.

Re: [PATCH v10 3/6] PCI: Refactor capability search into common macros

[Hans Zhang]

On 2025/4/30 16:03, Ilpo Järvinen wrote:
> On Tue, 29 Apr 2025, Hans Zhang wrote:
> 
>> The PCI Capability search functionality is duplicated across the PCI core
>> and several controller drivers. The core's current implementation requires
>> fully initialized PCI device and bus structures, which prevents controller
>> drivers from using it during early initialization phases before these
>> structures are available.
>>
>> Move the Capability search logic into a header-based macro that accepts a
>> config space accessor function as an argument. This enables controller
>> drivers to perform Capability discovery using their early access
>> mechanisms prior to full device initialization while sharing the
>> Capability search code.
>>
>> Convert the existing PCI core Capability search implementation to use this
>> new macro.
>>
>> The macros now implement, parameterized by the config access method. The
> 
> This sentence is incomplete (and sounds pretty much duplicated
> information anyway).
> 

Dear Ilpo,

Thank you very much for pointing out my problems patiently. These will 
be deleted.

>> PCI core functions are converted to utilize these macros with the standard
>> pci_bus_read_config accessors.
> 
> This info is duplicated.
> 

Will delete.

>> Controller drivers can later use the same
>> macros with their early access mechanisms while maintaining the existing
>> protection against infinite loops through preserved TTL checks.
>>
>> The ttl parameter was originally an additional safeguard to prevent
>> infinite loops in corrupted config space.  However, the
>> PCI_FIND_NEXT_CAP_TTL macro already enforces a TTL limit internally.
>> Removing redundant ttl handling simplifies the interface while maintaining
>> the safety guarantee. This aligns with the macro's design intent of
>> encapsulating TTL management.

Best regards,
Hans

[PATCH v10 4/6] PCI: dwc: Use common PCI host bridge APIs for finding the capabilities

[Hans Zhang]

Use the PCI core is now exposing generic macros for the host bridges to
search for the PCIe capabilities, make use of them in the DWC driver.

Signed-off-by: Hans Zhang <18255117159@163.com>
---
Changes since v9:
- Resolved [v9 4/6] compilation error.
  The latest 6.15 rc1 merge __dw_pcie_find_vsec_capability, which uses 
  dw_pcie_find_next_ext_capability.

Changes since v8:
- None

Changes since v7:
- Resolve compilation errors.

Changes since v6:
https://lore.kernel.org/linux-pci/20250323164852.430546-3-18255117159@163.com/

- The patch commit message were modified.

Changes since v5:
https://lore.kernel.org/linux-pci/20250321163803.391056-3-18255117159@163.com/

- Kconfig add "select PCI_HOST_HELPERS"
---
 drivers/pci/controller/dwc/pcie-designware.c | 76 +++-----------------
 1 file changed, 9 insertions(+), 67 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index 97d76d3dc066..837188f579a2 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -205,83 +205,25 @@ void dw_pcie_version_detect(struct dw_pcie *pci)
 		pci->type = ver;
 }
 
-/*
- * These interfaces resemble the pci_find_*capability() interfaces, but these
- * are for configuring host controllers, which are bridges *to* PCI devices but
- * are not PCI devices themselves.
- */
-static u8 __dw_pcie_find_next_cap(struct dw_pcie *pci, u8 cap_ptr,
-				  u8 cap)
+static int dw_pcie_read_cfg(void *priv, int where, int size, u32 *val)
 {
-	u8 cap_id, next_cap_ptr;
-	u16 reg;
-
-	if (!cap_ptr)
-		return 0;
-
-	reg = dw_pcie_readw_dbi(pci, cap_ptr);
-	cap_id = (reg & 0x00ff);
-
-	if (cap_id > PCI_CAP_ID_MAX)
-		return 0;
+	struct dw_pcie *pci = priv;
 
-	if (cap_id == cap)
-		return cap_ptr;
+	*val = dw_pcie_read_dbi(pci, where, size);
 
-	next_cap_ptr = (reg & 0xff00) >> 8;
-	return __dw_pcie_find_next_cap(pci, next_cap_ptr, cap);
+	return PCIBIOS_SUCCESSFUL;
 }
 
 u8 dw_pcie_find_capability(struct dw_pcie *pci, u8 cap)
 {
-	u8 next_cap_ptr;
-	u16 reg;
-
-	reg = dw_pcie_readw_dbi(pci, PCI_CAPABILITY_LIST);
-	next_cap_ptr = (reg & 0x00ff);
-
-	return __dw_pcie_find_next_cap(pci, next_cap_ptr, cap);
+	return PCI_FIND_NEXT_CAP_TTL(dw_pcie_read_cfg, PCI_CAPABILITY_LIST, cap,
+				     pci);
 }
 EXPORT_SYMBOL_GPL(dw_pcie_find_capability);
 
-static u16 dw_pcie_find_next_ext_capability(struct dw_pcie *pci, u16 start,
-					    u8 cap)
-{
-	u32 header;
-	int ttl;
-	int pos = PCI_CFG_SPACE_SIZE;
-
-	/* minimum 8 bytes per capability */
-	ttl = (PCI_CFG_SPACE_EXP_SIZE - PCI_CFG_SPACE_SIZE) / 8;
-
-	if (start)
-		pos = start;
-
-	header = dw_pcie_readl_dbi(pci, pos);
-	/*
-	 * If we have no capabilities, this is indicated by cap ID,
-	 * cap version and next pointer all being 0.
-	 */
-	if (header == 0)
-		return 0;
-
-	while (ttl-- > 0) {
-		if (PCI_EXT_CAP_ID(header) == cap && pos != start)
-			return pos;
-
-		pos = PCI_EXT_CAP_NEXT(header);
-		if (pos < PCI_CFG_SPACE_SIZE)
-			break;
-
-		header = dw_pcie_readl_dbi(pci, pos);
-	}
-
-	return 0;
-}
-
 u16 dw_pcie_find_ext_capability(struct dw_pcie *pci, u8 cap)
 {
-	return dw_pcie_find_next_ext_capability(pci, 0, cap);
+	return PCI_FIND_NEXT_EXT_CAPABILITY(dw_pcie_read_cfg, 0, cap, pci);
 }
 EXPORT_SYMBOL_GPL(dw_pcie_find_ext_capability);
 
@@ -294,8 +236,8 @@ static u16 __dw_pcie_find_vsec_capability(struct dw_pcie *pci, u16 vendor_id,
 	if (vendor_id != dw_pcie_readw_dbi(pci, PCI_VENDOR_ID))
 		return 0;
 
-	while ((vsec = dw_pcie_find_next_ext_capability(pci, vsec,
-						       PCI_EXT_CAP_ID_VNDR))) {
+	while ((vsec = PCI_FIND_NEXT_EXT_CAPABILITY(
+			dw_pcie_read_cfg, vsec, PCI_EXT_CAP_ID_VNDR, pci))) {
 		header = dw_pcie_readl_dbi(pci, vsec + PCI_VNDR_HEADER);
 		if (PCI_VNDR_HEADER_ID(header) == vsec_id)
 			return vsec;
-- 
2.25.1

[PATCH v10 5/6] PCI: cadence: Use common PCI host bridge APIs for finding the capabilities

[Hans Zhang]

Use the PCI core is now exposing generic macros for the host bridges to
search for the PCIe capabilities, make use of them in the CDNS driver.

Signed-off-by: Hans Zhang <18255117159@163.com>
---
Changes since v8 ~ v9:
- None

Changes since v7:
- Resolve compilation errors.

Changes since v6:
https://lore.kernel.org/linux-pci/20250323164852.430546-4-18255117159@163.com/

- The patch commit message were modified.

Changes since v5:
https://lore.kernel.org/linux-pci/20250321163803.391056-4-18255117159@163.com

- Kconfig add "select PCI_HOST_HELPERS"
---
 drivers/pci/controller/cadence/pcie-cadence.c | 28 +++++++++++++++++++
 drivers/pci/controller/cadence/pcie-cadence.h | 13 +++++++++
 2 files changed, 41 insertions(+)

diff --git a/drivers/pci/controller/cadence/pcie-cadence.c b/drivers/pci/controller/cadence/pcie-cadence.c
index 204e045aed8c..ca4a1a809fcb 100644
--- a/drivers/pci/controller/cadence/pcie-cadence.c
+++ b/drivers/pci/controller/cadence/pcie-cadence.c
@@ -7,6 +7,34 @@
 #include <linux/of.h>
 
 #include "pcie-cadence.h"
+#include "../../pci.h"
+
+static int cdns_pcie_read_cfg(void *priv, int where, int size, u32 *val)
+{
+	struct cdns_pcie *pcie = priv;
+
+	if (size == 4)
+		*val = cdns_pcie_readl(pcie, where);
+	else if (size == 2)
+		*val = cdns_pcie_readw(pcie, where);
+	else if (size == 1)
+		*val = cdns_pcie_readb(pcie, where);
+
+	return PCIBIOS_SUCCESSFUL;
+}
+
+u8 cdns_pcie_find_capability(struct cdns_pcie *pcie, u8 cap)
+{
+	return PCI_FIND_NEXT_CAP_TTL(cdns_pcie_read_cfg, PCI_CAPABILITY_LIST,
+				     cap, pcie);
+}
+EXPORT_SYMBOL_GPL(cdns_pcie_find_capability);
+
+u16 cdns_pcie_find_ext_capability(struct cdns_pcie *pcie, u8 cap)
+{
+	return PCI_FIND_NEXT_EXT_CAPABILITY(cdns_pcie_read_cfg, 0, cap, pcie);
+}
+EXPORT_SYMBOL_GPL(cdns_pcie_find_ext_capability);
 
 void cdns_pcie_detect_quiet_min_delay_set(struct cdns_pcie *pcie)
 {
diff --git a/drivers/pci/controller/cadence/pcie-cadence.h b/drivers/pci/controller/cadence/pcie-cadence.h
index 39ee9945c903..56d6a0e73eb7 100644
--- a/drivers/pci/controller/cadence/pcie-cadence.h
+++ b/drivers/pci/controller/cadence/pcie-cadence.h
@@ -398,6 +398,16 @@ static inline u32 cdns_pcie_readl(struct cdns_pcie *pcie, u32 reg)
 	return readl(pcie->reg_base + reg);
 }
 
+static inline u32 cdns_pcie_readw(struct cdns_pcie *pcie, u32 reg)
+{
+	return readw(pcie->reg_base + reg);
+}
+
+static inline u32 cdns_pcie_readb(struct cdns_pcie *pcie, u32 reg)
+{
+	return readb(pcie->reg_base + reg);
+}
+
 static inline u32 cdns_pcie_read_sz(void __iomem *addr, int size)
 {
 	void __iomem *aligned_addr = PTR_ALIGN_DOWN(addr, 0x4);
@@ -557,6 +567,9 @@ static inline int cdns_pcie_ep_setup(struct cdns_pcie_ep *ep)
 }
 #endif
 
+u8 cdns_pcie_find_capability(struct cdns_pcie *pcie, u8 cap);
+u16 cdns_pcie_find_ext_capability(struct cdns_pcie *pcie, u8 cap);
+
 void cdns_pcie_detect_quiet_min_delay_set(struct cdns_pcie *pcie);
 
 void cdns_pcie_set_outbound_region(struct cdns_pcie *pcie, u8 busnr, u8 fn,
-- 
2.25.1

[PATCH v10 6/6] PCI: cadence: Use cdns_pcie_find_*capability to avoid hardcode.

[Hans Zhang]

The PCIe capability/extended capability offsets are not guaranteed to be
the same across all SoCs integrating the Cadence PCIe IP. Hence, use the
cdns_pcie_find_{ext}_capability() APIs for finding them.

This avoids hardcoding the offsets in the driver.

Signed-off-by: Hans Zhang <18255117159@163.com>
---
Changes since v8 ~ v9:
- None

Changes since v7:
- Resolve compilation errors.

Changes since v6:
https://lore.kernel.org/linux-pci/20250323164852.430546-4-18255117159@163.com/

- The patch commit message were modified.

Changes since v5:
https://lore.kernel.org/linux-pci/20250321163803.391056-4-18255117159@163.com

- Kconfig add "select PCI_HOST_HELPERS"
---
 .../pci/controller/cadence/pcie-cadence-ep.c  | 40 +++++++++++--------
 drivers/pci/controller/cadence/pcie-cadence.h |  5 ---
 2 files changed, 23 insertions(+), 22 deletions(-)

diff --git a/drivers/pci/controller/cadence/pcie-cadence-ep.c b/drivers/pci/controller/cadence/pcie-cadence-ep.c
index 599ec4b1223e..5c4b2151d181 100644
--- a/drivers/pci/controller/cadence/pcie-cadence-ep.c
+++ b/drivers/pci/controller/cadence/pcie-cadence-ep.c
@@ -19,12 +19,13 @@
 
 static u8 cdns_pcie_get_fn_from_vfn(struct cdns_pcie *pcie, u8 fn, u8 vfn)
 {
-	u32 cap = CDNS_PCIE_EP_FUNC_SRIOV_CAP_OFFSET;
 	u32 first_vf_offset, stride;
+	u16 cap;
 
 	if (vfn == 0)
 		return fn;
 
+	cap = cdns_pcie_find_ext_capability(pcie, PCI_EXT_CAP_ID_SRIOV);
 	first_vf_offset = cdns_pcie_ep_fn_readw(pcie, fn, cap + PCI_SRIOV_VF_OFFSET);
 	stride = cdns_pcie_ep_fn_readw(pcie, fn, cap +  PCI_SRIOV_VF_STRIDE);
 	fn = fn + first_vf_offset + ((vfn - 1) * stride);
@@ -36,10 +37,11 @@ static int cdns_pcie_ep_write_header(struct pci_epc *epc, u8 fn, u8 vfn,
 				     struct pci_epf_header *hdr)
 {
 	struct cdns_pcie_ep *ep = epc_get_drvdata(epc);
-	u32 cap = CDNS_PCIE_EP_FUNC_SRIOV_CAP_OFFSET;
 	struct cdns_pcie *pcie = &ep->pcie;
 	u32 reg;
+	u16 cap;
 
+	cap = cdns_pcie_find_ext_capability(pcie, PCI_EXT_CAP_ID_SRIOV);
 	if (vfn > 1) {
 		dev_err(&epc->dev, "Only Virtual Function #1 has deviceID\n");
 		return -EINVAL;
@@ -224,9 +226,10 @@ static int cdns_pcie_ep_set_msi(struct pci_epc *epc, u8 fn, u8 vfn, u8 mmc)
 {
 	struct cdns_pcie_ep *ep = epc_get_drvdata(epc);
 	struct cdns_pcie *pcie = &ep->pcie;
-	u32 cap = CDNS_PCIE_EP_FUNC_MSI_CAP_OFFSET;
 	u16 flags;
+	u8 cap;
 
+	cap = cdns_pcie_find_capability(pcie, PCI_CAP_ID_MSI);
 	fn = cdns_pcie_get_fn_from_vfn(pcie, fn, vfn);
 
 	/*
@@ -246,9 +249,10 @@ static int cdns_pcie_ep_get_msi(struct pci_epc *epc, u8 fn, u8 vfn)
 {
 	struct cdns_pcie_ep *ep = epc_get_drvdata(epc);
 	struct cdns_pcie *pcie = &ep->pcie;
-	u32 cap = CDNS_PCIE_EP_FUNC_MSI_CAP_OFFSET;
 	u16 flags, mme;
+	u8 cap;
 
+	cap = cdns_pcie_find_capability(pcie, PCI_CAP_ID_MSI);
 	fn = cdns_pcie_get_fn_from_vfn(pcie, fn, vfn);
 
 	/* Validate that the MSI feature is actually enabled. */
@@ -269,9 +273,10 @@ static int cdns_pcie_ep_get_msix(struct pci_epc *epc, u8 func_no, u8 vfunc_no)
 {
 	struct cdns_pcie_ep *ep = epc_get_drvdata(epc);
 	struct cdns_pcie *pcie = &ep->pcie;
-	u32 cap = CDNS_PCIE_EP_FUNC_MSIX_CAP_OFFSET;
 	u32 val, reg;
+	u8 cap;
 
+	cap = cdns_pcie_find_capability(pcie, PCI_CAP_ID_MSIX);
 	func_no = cdns_pcie_get_fn_from_vfn(pcie, func_no, vfunc_no);
 
 	reg = cap + PCI_MSIX_FLAGS;
@@ -290,9 +295,10 @@ static int cdns_pcie_ep_set_msix(struct pci_epc *epc, u8 fn, u8 vfn,
 {
 	struct cdns_pcie_ep *ep = epc_get_drvdata(epc);
 	struct cdns_pcie *pcie = &ep->pcie;
-	u32 cap = CDNS_PCIE_EP_FUNC_MSIX_CAP_OFFSET;
 	u32 val, reg;
+	u8 cap;
 
+	cap = cdns_pcie_find_capability(pcie, PCI_CAP_ID_MSIX);
 	fn = cdns_pcie_get_fn_from_vfn(pcie, fn, vfn);
 
 	reg = cap + PCI_MSIX_FLAGS;
@@ -378,11 +384,11 @@ static int cdns_pcie_ep_send_msi_irq(struct cdns_pcie_ep *ep, u8 fn, u8 vfn,
 				     u8 interrupt_num)
 {
 	struct cdns_pcie *pcie = &ep->pcie;
-	u32 cap = CDNS_PCIE_EP_FUNC_MSI_CAP_OFFSET;
 	u16 flags, mme, data, data_mask;
-	u8 msi_count;
 	u64 pci_addr, pci_addr_mask = 0xff;
+	u8 msi_count, cap;
 
+	cap = cdns_pcie_find_capability(pcie, PCI_CAP_ID_MSI);
 	fn = cdns_pcie_get_fn_from_vfn(pcie, fn, vfn);
 
 	/* Check whether the MSI feature has been enabled by the PCI host. */
@@ -430,14 +436,14 @@ static int cdns_pcie_ep_map_msi_irq(struct pci_epc *epc, u8 fn, u8 vfn,
 				    u32 *msi_addr_offset)
 {
 	struct cdns_pcie_ep *ep = epc_get_drvdata(epc);
-	u32 cap = CDNS_PCIE_EP_FUNC_MSI_CAP_OFFSET;
 	struct cdns_pcie *pcie = &ep->pcie;
 	u64 pci_addr, pci_addr_mask = 0xff;
 	u16 flags, mme, data, data_mask;
-	u8 msi_count;
+	u8 msi_count, cap;
 	int ret;
 	int i;
 
+	cap = cdns_pcie_find_capability(pcie, PCI_CAP_ID_MSI);
 	fn = cdns_pcie_get_fn_from_vfn(pcie, fn, vfn);
 
 	/* Check whether the MSI feature has been enabled by the PCI host. */
@@ -480,16 +486,16 @@ static int cdns_pcie_ep_map_msi_irq(struct pci_epc *epc, u8 fn, u8 vfn,
 static int cdns_pcie_ep_send_msix_irq(struct cdns_pcie_ep *ep, u8 fn, u8 vfn,
 				      u16 interrupt_num)
 {
-	u32 cap = CDNS_PCIE_EP_FUNC_MSIX_CAP_OFFSET;
 	u32 tbl_offset, msg_data, reg;
 	struct cdns_pcie *pcie = &ep->pcie;
 	struct pci_epf_msix_tbl *msix_tbl;
 	struct cdns_pcie_epf *epf;
 	u64 pci_addr_mask = 0xff;
 	u64 msg_addr;
+	u8 bir, cap;
 	u16 flags;
-	u8 bir;
 
+	cap = cdns_pcie_find_capability(pcie, PCI_CAP_ID_MSIX);
 	epf = &ep->epf[fn];
 	if (vfn > 0)
 		epf = &epf->epf[vfn - 1];
@@ -563,7 +569,9 @@ static int cdns_pcie_ep_start(struct pci_epc *epc)
 	int max_epfs = sizeof(epc->function_num_map) * 8;
 	int ret, epf, last_fn;
 	u32 reg, value;
+	u8 cap;
 
+	cap = cdns_pcie_find_capability(pcie, PCI_CAP_ID_EXP);
 	/*
 	 * BIT(0) is hardwired to 1, hence function 0 is always enabled
 	 * and can't be disabled anyway.
@@ -587,12 +595,10 @@ static int cdns_pcie_ep_start(struct pci_epc *epc)
 				continue;
 
 			value = cdns_pcie_ep_fn_readl(pcie, epf,
-					CDNS_PCIE_EP_FUNC_DEV_CAP_OFFSET +
-					PCI_EXP_DEVCAP);
+						      cap + PCI_EXP_DEVCAP);
 			value &= ~PCI_EXP_DEVCAP_FLR;
-			cdns_pcie_ep_fn_writel(pcie, epf,
-					CDNS_PCIE_EP_FUNC_DEV_CAP_OFFSET +
-					PCI_EXP_DEVCAP, value);
+			cdns_pcie_ep_fn_writel(pcie, epf, cap + PCI_EXP_DEVCAP,
+					       value);
 		}
 	}
 
diff --git a/drivers/pci/controller/cadence/pcie-cadence.h b/drivers/pci/controller/cadence/pcie-cadence.h
index 56d6a0e73eb7..08491275349d 100644
--- a/drivers/pci/controller/cadence/pcie-cadence.h
+++ b/drivers/pci/controller/cadence/pcie-cadence.h
@@ -125,11 +125,6 @@
  */
 #define CDNS_PCIE_EP_FUNC_BASE(fn)	(((fn) << 12) & GENMASK(19, 12))
 
-#define CDNS_PCIE_EP_FUNC_MSI_CAP_OFFSET	0x90
-#define CDNS_PCIE_EP_FUNC_MSIX_CAP_OFFSET	0xb0
-#define CDNS_PCIE_EP_FUNC_DEV_CAP_OFFSET	0xc0
-#define CDNS_PCIE_EP_FUNC_SRIOV_CAP_OFFSET	0x200
-
 /*
  * Endpoint PF Registers
  */
-- 
2.25.1