linux-kernel - [PATCH] misc: eeprom: Fix EWEN/EWDS/ERAL commands for 93xx56 and 93xx66

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Message-ID: <20251202104823.429869-3-markus@notsyncing.net>
Date: Tue,  2 Dec 2025 11:48:24 +0100
From: Markus Perkins <markus@...syncing.net>
To: Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: agust@...x.de,
	linkmauve@...kmauve.fr,
	Markus Perkins <markus@...syncing.net>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] misc: eeprom: Fix EWEN/EWDS/ERAL commands for 93xx56 and 93xx66

commit 14374fbb3f06 ("misc: eeprom_93xx46: Add new 93c56 and 93c66
compatible strings") added support for 93xx56 and 93xx66 eeproms, but
didn't take into account that the write enable/disable + erase all
commands are hardcoded for the 6-bit address of the 93xx46.

This commit fixes the command word generation by increasing the number
of shifts as the address field grows, keeping the command intact.

Also, the check for 8-bit or 16-bit mode is no longer required as this
is already taken into account in the edev->addrlen field.

Signed-off-by: Markus Perkins <markus@...syncing.net>
---
I verified this update with an AT93C66 EEPROM connected to a Raspberry Pi
3 with the gpio-spi driver. (I need the gpio-spi driver because the
Broadcom SoC only supports 8-bit SPI transfer lengths.)

Here are the waveforms recorded by my logic analyzer (write command):
* Before: https://notsyncing.net/downloads/scrot/93c66_broken.png
* After: https://notsyncing.net/downloads/scrot/93c66_fixed.png

CC'ing Emmanuel and Anatolij as potential reviewers.

 drivers/misc/eeprom/eeprom_93xx46.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/drivers/misc/eeprom/eeprom_93xx46.c b/drivers/misc/eeprom/eeprom_93xx46.c
index 9cae6f530679..5230e910a1d1 100644
--- a/drivers/misc/eeprom/eeprom_93xx46.c
+++ b/drivers/misc/eeprom/eeprom_93xx46.c
@@ -45,6 +45,7 @@ struct eeprom_93xx46_platform_data {
 #define OP_START	0x4
 #define OP_WRITE	(OP_START | 0x1)
 #define OP_READ		(OP_START | 0x2)
+/* The following addresses are offset for the 1K EEPROM variant in 16-bit mode */
 #define ADDR_EWDS	0x00
 #define ADDR_ERAL	0x20
 #define ADDR_EWEN	0x30
@@ -191,10 +192,7 @@ static int eeprom_93xx46_ew(struct eeprom_93xx46_dev *edev, int is_on)
 	bits = edev->addrlen + 3;
 
 	cmd_addr = OP_START << edev->addrlen;
-	if (edev->pdata->flags & EE_ADDR8)
-		cmd_addr |= (is_on ? ADDR_EWEN : ADDR_EWDS) << 1;
-	else
-		cmd_addr |= (is_on ? ADDR_EWEN : ADDR_EWDS);
+	cmd_addr |= (is_on ? ADDR_EWEN : ADDR_EWDS) << (edev->addrlen - 6);
 
 	if (has_quirk_instruction_length(edev)) {
 		cmd_addr <<= 2;
@@ -328,10 +326,7 @@ static int eeprom_93xx46_eral(struct eeprom_93xx46_dev *edev)
 	bits = edev->addrlen + 3;
 
 	cmd_addr = OP_START << edev->addrlen;
-	if (edev->pdata->flags & EE_ADDR8)
-		cmd_addr |= ADDR_ERAL << 1;
-	else
-		cmd_addr |= ADDR_ERAL;
+	cmd_addr |= ADDR_ERAL << (edev->addrlen - 6);
 
 	if (has_quirk_instruction_length(edev)) {
 		cmd_addr <<= 2;
-- 
2.51.2