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

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Message-ID: <20260120130603.1066559-1-patrick@subset.ch>
Date: Tue, 20 Jan 2026 14:06:02 +0100
From: patrick@...set.ch
To: linux-kernel@...r.kernel.org
Cc: alexander.sverdlin@...mens.com,
	gregkh@...uxfoundation.org,
	arnd@...db.de,
	Patrick Wicki <patrick.wicki@...mens.com>
Subject: [PATCH 1/2] eeprom: at25: add support for Infineon Cypress QSN FRAMs

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>
---
 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)
-- 
2.52.0