[PATCH 0/3] eeprom: at25: support Cypress FRAMs without device ID

[PATCH 0/3] eeprom: at25: support Cypress FRAMs without device ID

[Markus Heidelberg]

Hello,

currently supported FRAMs use compatible="cypress,fm25","atmel,at25" in
Devicetree, the memory size is read from its device ID.
For FRAMs without device ID this is not possible, so with these patches
the "size" property can be set manually as it is done for EEPROMs. In
that case the device ID is not read anymore.

This patch series is basically the same as the one marked as RFC four
months ago:

  https://lore.kernel.org/all/20250401133148.38330-1-m.heidelberg@cab.de/

Based on v6.17-rc1 now and extended by a comment to the at25 binding.

Markus Heidelberg (3):
  dt-bindings: eeprom: at25: use "size" for FRAMs without device ID
  eeprom: at25: support Cypress FRAMs without device ID
  eeprom: at25: make FRAM device ID error message more precise

 .../devicetree/bindings/eeprom/at25.yaml      |  1 +
 drivers/misc/eeprom/at25.c                    | 67 ++++++++++---------
 2 files changed, 37 insertions(+), 31 deletions(-)


base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585
-- 
2.43.0

[PATCH 1/3] dt-bindings: eeprom: at25: use "size" for FRAMs without device ID

[Markus Heidelberg]

Link: https://lore.kernel.org/all/20250401133148.38330-1-m.heidelberg@cab.de/
Signed-off-by: Markus Heidelberg <m.heidelberg@cab.de>
---
 Documentation/devicetree/bindings/eeprom/at25.yaml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Documentation/devicetree/bindings/eeprom/at25.yaml b/Documentation/devicetree/bindings/eeprom/at25.yaml
index c31e5e719525..d6fe84091ad4 100644
--- a/Documentation/devicetree/bindings/eeprom/at25.yaml
+++ b/Documentation/devicetree/bindings/eeprom/at25.yaml
@@ -56,6 +56,7 @@ properties:
     $ref: /schemas/types.yaml#/definitions/uint32
     description:
       Total eeprom size in bytes.
+      Also used for FRAMs without device ID where the size cannot be detected.
 
   address-width:
     $ref: /schemas/types.yaml#/definitions/uint32
-- 
2.43.0

[PATCH 2/3] eeprom: at25: support Cypress FRAMs without device ID

[Markus Heidelberg]

Not all FRAM chips have a device ID and implement the corresponding read
command. For such chips this led to the following error on module
loading:

    at25 spi2.0: Error: no Cypress FRAM (id 00)

The device ID contains the memory size, so devices without this ID are
supported now by setting the size manually in Devicetree using the
"size" property.

Tested with FM25L16B and "size = <2048>;":

    at25 spi2.0: 2 KByte fm25 fram, pagesize 4096

According to Infineon/Cypress datasheets, these FRAMs have a device ID:

    FM25V01A
    FM25V02A
    FM25V05
    FM25V10
    FM25V20A
    FM25VN10

but these do not:

    FM25040B
    FM25640B
    FM25C160B
    FM25CL64B
    FM25L04B
    FM25L16B
    FM25W256

So all "FM25V*" FRAMs and only these have a device ID. The letter after
"FM25" (V/C/L/W) only describes the voltage range, though.

Link: https://lore.kernel.org/all/20250401133148.38330-1-m.heidelberg@cab.de/
Signed-off-by: Markus Heidelberg <m.heidelberg@cab.de>
---
 drivers/misc/eeprom/at25.c | 67 ++++++++++++++++++++------------------
 1 file changed, 36 insertions(+), 31 deletions(-)

diff --git a/drivers/misc/eeprom/at25.c b/drivers/misc/eeprom/at25.c
index 2d0492867054..c90150f72836 100644
--- a/drivers/misc/eeprom/at25.c
+++ b/drivers/misc/eeprom/at25.c
@@ -379,37 +379,49 @@ static int at25_fram_to_chip(struct device *dev, struct spi_eeprom *chip)
 	struct at25_data *at25 = container_of(chip, struct at25_data, chip);
 	u8 sernum[FM25_SN_LEN];
 	u8 id[FM25_ID_LEN];
+	u32 val;
 	int i;
 
 	strscpy(chip->name, "fm25", sizeof(chip->name));
 
-	/* Get ID of chip */
-	fm25_aux_read(at25, id, FM25_RDID, FM25_ID_LEN);
-	/* There are inside-out FRAM variations, detect them and reverse the ID bytes */
-	if (id[6] == 0x7f && id[2] == 0xc2)
-		for (i = 0; i < ARRAY_SIZE(id) / 2; i++) {
-			u8 tmp = id[i];
-			int j = ARRAY_SIZE(id) - i - 1;
+	if (!device_property_read_u32(dev, "size", &val)) {
+		chip->byte_len = val;
+	} else {
+		/* Get ID of chip */
+		fm25_aux_read(at25, id, FM25_RDID, FM25_ID_LEN);
+		/* There are inside-out FRAM variations, detect them and reverse the ID bytes */
+		if (id[6] == 0x7f && id[2] == 0xc2)
+			for (i = 0; i < ARRAY_SIZE(id) / 2; i++) {
+				u8 tmp = id[i];
+				int j = ARRAY_SIZE(id) - i - 1;
+
+				id[i] = id[j];
+				id[j] = tmp;
+			}
+		if (id[6] != 0xc2) {
+			dev_err(dev, "Error: no Cypress FRAM (id %02x)\n", id[6]);
+			return -ENODEV;
+		}
 
-			id[i] = id[j];
-			id[j] = tmp;
+		switch (id[7]) {
+		case 0x21 ... 0x26:
+			chip->byte_len = BIT(id[7] - 0x21 + 4) * 1024;
+			break;
+		case 0x2a ... 0x30:
+			/* CY15B116QN ... CY15B116QN */
+			chip->byte_len = BIT(((id[7] >> 1) & 0xf) + 13);
+			break;
+		default:
+			dev_err(dev, "Error: unsupported size (id %02x)\n", id[7]);
+			return -ENODEV;
 		}
-	if (id[6] != 0xc2) {
-		dev_err(dev, "Error: no Cypress FRAM (id %02x)\n", id[6]);
-		return -ENODEV;
-	}
 
-	switch (id[7]) {
-	case 0x21 ... 0x26:
-		chip->byte_len = BIT(id[7] - 0x21 + 4) * 1024;
-		break;
-	case 0x2a ... 0x30:
-		/* CY15B116QN ... CY15B116QN */
-		chip->byte_len = BIT(((id[7] >> 1) & 0xf) + 13);
-		break;
-	default:
-		dev_err(dev, "Error: unsupported size (id %02x)\n", id[7]);
-		return -ENODEV;
+		if (id[8]) {
+			fm25_aux_read(at25, sernum, FM25_RDSN, FM25_SN_LEN);
+			/* Swap byte order */
+			for (i = 0; i < FM25_SN_LEN; i++)
+				at25->sernum[i] = sernum[FM25_SN_LEN - 1 - i];
+		}
 	}
 
 	if (chip->byte_len > 64 * 1024)
@@ -417,13 +429,6 @@ static int at25_fram_to_chip(struct device *dev, struct spi_eeprom *chip)
 	else
 		chip->flags |= EE_ADDR2;
 
-	if (id[8]) {
-		fm25_aux_read(at25, sernum, FM25_RDSN, FM25_SN_LEN);
-		/* Swap byte order */
-		for (i = 0; i < FM25_SN_LEN; i++)
-			at25->sernum[i] = sernum[FM25_SN_LEN - 1 - i];
-	}
-
 	chip->page_size = PAGE_SIZE;
 	return 0;
 }
-- 
2.43.0

[PATCH 3/3] eeprom: at25: make FRAM device ID error message more precise

[Markus Heidelberg]

The error description would be wrong in case the "size" Devicetree
property is missing for an FRAM without device ID.

Signed-off-by: Markus Heidelberg <m.heidelberg@cab.de>
---
 drivers/misc/eeprom/at25.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/misc/eeprom/at25.c b/drivers/misc/eeprom/at25.c
index c90150f72836..e2868f7bdb03 100644
--- a/drivers/misc/eeprom/at25.c
+++ b/drivers/misc/eeprom/at25.c
@@ -399,7 +399,7 @@ static int at25_fram_to_chip(struct device *dev, struct spi_eeprom *chip)
 				id[j] = tmp;
 			}
 		if (id[6] != 0xc2) {
-			dev_err(dev, "Error: no Cypress FRAM (id %02x)\n", id[6]);
+			dev_err(dev, "Error: no Cypress FRAM with device ID (manufacturer ID bank 7: %02x)\n", id[6]);
 			return -ENODEV;
 		}
 
-- 
2.43.0

Re: [PATCH 2/3] eeprom: at25: support Cypress FRAMs without device ID

[Alexander Sverdlin]

On Thu, 2025-08-14 at 13:15 +0200, Markus Heidelberg wrote:
> Not all FRAM chips have a device ID and implement the corresponding read
> command. For such chips this led to the following error on module
> loading:
> 
>     at25 spi2.0: Error: no Cypress FRAM (id 00)
> 
> The device ID contains the memory size, so devices without this ID are
> supported now by setting the size manually in Devicetree using the
> "size" property.
> 
> Tested with FM25L16B and "size = <2048>;":
> 
>     at25 spi2.0: 2 KByte fm25 fram, pagesize 4096
> 
> According to Infineon/Cypress datasheets, these FRAMs have a device ID:
> 
>     FM25V01A
>     FM25V02A
>     FM25V05
>     FM25V10
>     FM25V20A
>     FM25VN10
> 
> but these do not:
> 
>     FM25040B
>     FM25640B
>     FM25C160B
>     FM25CL64B
>     FM25L04B
>     FM25L16B
>     FM25W256
> 
> So all "FM25V*" FRAMs and only these have a device ID. The letter after
> "FM25" (V/C/L/W) only describes the voltage range, though.
> 
> Link: https://lore.kernel.org/all/20250401133148.38330-1-m.heidelberg@cab.de/
> Signed-off-by: Markus Heidelberg <m.heidelberg@cab.de>

Reviewed-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>

> ---
>  drivers/misc/eeprom/at25.c | 67 ++++++++++++++++++++------------------
>  1 file changed, 36 insertions(+), 31 deletions(-)
> 
> diff --git a/drivers/misc/eeprom/at25.c b/drivers/misc/eeprom/at25.c
> index 2d0492867054..c90150f72836 100644
> --- a/drivers/misc/eeprom/at25.c
> +++ b/drivers/misc/eeprom/at25.c
> @@ -379,37 +379,49 @@ static int at25_fram_to_chip(struct device *dev, struct spi_eeprom *chip)
>  	struct at25_data *at25 = container_of(chip, struct at25_data, chip);
>  	u8 sernum[FM25_SN_LEN];
>  	u8 id[FM25_ID_LEN];
> +	u32 val;
>  	int i;
>  
>  	strscpy(chip->name, "fm25", sizeof(chip->name));
>  
> -	/* Get ID of chip */
> -	fm25_aux_read(at25, id, FM25_RDID, FM25_ID_LEN);
> -	/* There are inside-out FRAM variations, detect them and reverse the ID bytes */
> -	if (id[6] == 0x7f && id[2] == 0xc2)
> -		for (i = 0; i < ARRAY_SIZE(id) / 2; i++) {
> -			u8 tmp = id[i];
> -			int j = ARRAY_SIZE(id) - i - 1;
> +	if (!device_property_read_u32(dev, "size", &val)) {
> +		chip->byte_len = val;
> +	} else {
> +		/* Get ID of chip */
> +		fm25_aux_read(at25, id, FM25_RDID, FM25_ID_LEN);
> +		/* There are inside-out FRAM variations, detect them and reverse the ID bytes */
> +		if (id[6] == 0x7f && id[2] == 0xc2)
> +			for (i = 0; i < ARRAY_SIZE(id) / 2; i++) {
> +				u8 tmp = id[i];
> +				int j = ARRAY_SIZE(id) - i - 1;
> +
> +				id[i] = id[j];
> +				id[j] = tmp;
> +			}
> +		if (id[6] != 0xc2) {
> +			dev_err(dev, "Error: no Cypress FRAM (id %02x)\n", id[6]);
> +			return -ENODEV;
> +		}
>  
> -			id[i] = id[j];
> -			id[j] = tmp;
> +		switch (id[7]) {
> +		case 0x21 ... 0x26:
> +			chip->byte_len = BIT(id[7] - 0x21 + 4) * 1024;
> +			break;
> +		case 0x2a ... 0x30:
> +			/* CY15B116QN ... CY15B116QN */
> +			chip->byte_len = BIT(((id[7] >> 1) & 0xf) + 13);
> +			break;
> +		default:
> +			dev_err(dev, "Error: unsupported size (id %02x)\n", id[7]);
> +			return -ENODEV;
>  		}
> -	if (id[6] != 0xc2) {
> -		dev_err(dev, "Error: no Cypress FRAM (id %02x)\n", id[6]);
> -		return -ENODEV;
> -	}
>  
> -	switch (id[7]) {
> -	case 0x21 ... 0x26:
> -		chip->byte_len = BIT(id[7] - 0x21 + 4) * 1024;
> -		break;
> -	case 0x2a ... 0x30:
> -		/* CY15B116QN ... CY15B116QN */
> -		chip->byte_len = BIT(((id[7] >> 1) & 0xf) + 13);
> -		break;
> -	default:
> -		dev_err(dev, "Error: unsupported size (id %02x)\n", id[7]);
> -		return -ENODEV;
> +		if (id[8]) {
> +			fm25_aux_read(at25, sernum, FM25_RDSN, FM25_SN_LEN);
> +			/* Swap byte order */
> +			for (i = 0; i < FM25_SN_LEN; i++)
> +				at25->sernum[i] = sernum[FM25_SN_LEN - 1 - i];
> +		}
>  	}
>  
>  	if (chip->byte_len > 64 * 1024)
> @@ -417,13 +429,6 @@ static int at25_fram_to_chip(struct device *dev, struct spi_eeprom *chip)
>  	else
>  		chip->flags |= EE_ADDR2;
>  
> -	if (id[8]) {
> -		fm25_aux_read(at25, sernum, FM25_RDSN, FM25_SN_LEN);
> -		/* Swap byte order */
> -		for (i = 0; i < FM25_SN_LEN; i++)
> -			at25->sernum[i] = sernum[FM25_SN_LEN - 1 - i];
> -	}
> -
>  	chip->page_size = PAGE_SIZE;
>  	return 0;
>  }
> --
> 2.43.0

-- 
Alexander Sverdlin.

Re: [PATCH 3/3] eeprom: at25: make FRAM device ID error message more precise

[Alexander Sverdlin]

On Thu, 2025-08-14 at 13:15 +0200, Markus Heidelberg wrote:
> The error description would be wrong in case the "size" Devicetree
> property is missing for an FRAM without device ID.
> 
> Signed-off-by: Markus Heidelberg <m.heidelberg@cab.de>

Reviewed-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>

> ---
>  drivers/misc/eeprom/at25.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/misc/eeprom/at25.c b/drivers/misc/eeprom/at25.c
> index c90150f72836..e2868f7bdb03 100644
> --- a/drivers/misc/eeprom/at25.c
> +++ b/drivers/misc/eeprom/at25.c
> @@ -399,7 +399,7 @@ static int at25_fram_to_chip(struct device *dev, struct spi_eeprom *chip)
>  				id[j] = tmp;
>  			}
>  		if (id[6] != 0xc2) {
> -			dev_err(dev, "Error: no Cypress FRAM (id %02x)\n", id[6]);
> +			dev_err(dev, "Error: no Cypress FRAM with device ID (manufacturer ID bank 7: %02x)\n", id[6]);
>  			return -ENODEV;
>  		}

-- 
Alexander Sverdlin.

Re: [PATCH 1/3] dt-bindings: eeprom: at25: use "size" for FRAMs without device ID

[Conor Dooley]

[-- Attachment #1: Type: text/plain, Size: 998 bytes --]

On Thu, Aug 14, 2025 at 01:15:30PM +0200, Markus Heidelberg wrote:
> Link: https://lore.kernel.org/all/20250401133148.38330-1-m.heidelberg@cab.de/
> Signed-off-by: Markus Heidelberg <m.heidelberg@cab.de>

Missing commit message body explaining why this change is needed.

> ---
>  Documentation/devicetree/bindings/eeprom/at25.yaml | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/Documentation/devicetree/bindings/eeprom/at25.yaml b/Documentation/devicetree/bindings/eeprom/at25.yaml
> index c31e5e719525..d6fe84091ad4 100644
> --- a/Documentation/devicetree/bindings/eeprom/at25.yaml
> +++ b/Documentation/devicetree/bindings/eeprom/at25.yaml
> @@ -56,6 +56,7 @@ properties:
>      $ref: /schemas/types.yaml#/definitions/uint32
>      description:
>        Total eeprom size in bytes.
> +      Also used for FRAMs without device ID where the size cannot be detected.
>  
>    address-width:
>      $ref: /schemas/types.yaml#/definitions/uint32
> -- 
> 2.43.0
> 

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