linux-kernel - Re: [PATCH 1/2] eeprom: at25: add support for Infineon Cypress QSN FRAMs

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Message-ID: <e8c4aaf1a340809485f7e6857cdaa994af446fe9.camel@siemens.com>
Date: Wed, 21 Jan 2026 08:58:21 +0000
From: "Sverdlin, Alexander" <alexander.sverdlin@...mens.com>
To: "patrick@...set.ch" <patrick@...set.ch>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
CC: "Wicki, Patrick" <patrick.wicki@...mens.com>
Subject: Re: [PATCH 1/2] eeprom: at25: add support for Infineon Cypress QSN
 FRAMs

On Tue, 2026-01-20 at 14:06 +0100, patrick@...set.ch wrote:
> From: Patrick Wicki <patrick.wicki@...mens.com>
> 
> Add support for Infineon Cypress CY15****QSN FRAM chips.
> Unlike the QN variants these chips have an 8 byte JEDEC ID.
> 
> The layout of the serial number matches that of already supported chips
> like the CY15B204QN, so make the read-out unconditional.
> 
> Tested with the CY15B204QSN. According to Infineon datasheets, all QSN
> variants appear to share a consistent pattern so the size should be
> correctly detected based on the density bits in the ID:
> 
> CY15B201QSN: 0x00 00 00 00 06 82 54 40, density_id:  8: 1Mb
> CY15B102QSN: 0x00 00 00 00 06 82 51 48, density_id:  9: 2Mb
> CY15B204QSN: 0x00 00 00 00 06 82 54 50, density_id: 10: 4Mb
> CY15V108QSN: 0x00 00 00 00 06 82 52 58, density_id: 11: 8Mb
> 
> Signed-off-by: Patrick Wicki <patrick.wicki@...mens.com>

Tested with CY15B204QSN:

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

> ---
>  drivers/misc/eeprom/at25.c | 50 +++++++++++++++++++++++---------------
>  1 file changed, 30 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/misc/eeprom/at25.c b/drivers/misc/eeprom/at25.c
> index 883dfd0ed6583..5b00921d07d2e 100644
> --- a/drivers/misc/eeprom/at25.c
> +++ b/drivers/misc/eeprom/at25.c
> @@ -398,30 +398,40 @@ static int at25_fram_to_chip(struct device *dev, struct spi_eeprom *chip)
>  				id[i] = id[j];
>  				id[j] = tmp;
>  			}
> -		if (id[6] != 0xc2) {
> -			dev_err(dev, "Error: no Cypress FRAM with device ID (manufacturer ID bank 7: %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:
> -			/* CY15B102QN ... CY15B116QN */
> -			chip->byte_len = BIT(((id[7] >> 1) & 0xf) + 13);
> -			break;
> -		default:
> -			dev_err(dev, "Error: unsupported size (id %02x)\n", id[7]);
> +		if (id[6] == 0xc2) {
> +			switch (id[7]) {
> +			case 0x21 ... 0x26:
> +				chip->byte_len = BIT(id[7] - 0x21 + 4) * 1024;
> +				break;
> +			case 0x2a ... 0x30:
> +				/* CY15B102QN ... 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;
> +			}
> +		} else if (id[2] == 0x82 && id[3] == 0x06) {
> +			switch (id[1]) {
> +			case 0x51 ... 0x54:
> +				/* CY15B102QSN ... CY15B204QSN */
> +				chip->byte_len = BIT(((id[0] >> 3) & 0x1F) + 9);
> +				break;
> +			default:
> +				dev_err(dev, "Error: unsupported product id %02x\n", id[1]);
> +				return -ENODEV;
> +			}
> +		} else {
> +			dev_err(dev, "Error: unrecognized JEDEC ID format: %*ph\n",
> +				FM25_ID_LEN, id);
>  			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];
> -		}
> +		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)

-- 
Alexander Sverdlin
Siemens AG
www.siemens.com