[PATCH] board: ti: common: board_detect: Fix EEPROM read quirk

[Matwey V. Kornilov]

There are three different kinds of EEPROM possibly present on boards.
  1. 1byte address. For those we should avoid 2byte address in order
     not to rewrite the data. Second byte of the address can potentially
     be interpreted as the data to write.
  2. 2byte address with defined behaviour. When we try to use 1byte
     address they just return "FF FF FF FF ... FF"
  3. 2byte address with undefined behaviour (for instance, 24LC32AI).
     When we try to use 1byte address, then their internal read
     pointer is changed to some value. Subsequential reads may be
     broken.

To gracefully handle both case #1 and case #3 we read all required
data from EEPROM at once (about 80 bytes). So either all the data is
valid or we fallback to 2byte address.

Cc: Nishanth Menon <nm at ti.com>
Fixes: a58147c2dbbf ("board: ti: common: board_detect: Do 1byte address checks first.")
Reference: https://lore.kernel.org/all/CAJs94Ebdd4foOjhGFu9Bop0v=B1US9neDLxfhgcY23ukgLzFOQ@mail.gmail.com/
Signed-off-by: Matwey V. Kornilov <matwey.kornilov at gmail.com>
---
 board/ti/common/board_detect.c | 26 ++++++++------------------
 1 file changed, 8 insertions(+), 18 deletions(-)

diff --git a/board/ti/common/board_detect.c b/board/ti/common/board_detect.c
index ed34991377..fdf83fcfb0 100644
--- a/board/ti/common/board_detect.c
+++ b/board/ti/common/board_detect.c
@@ -86,7 +86,6 @@ __weak void gpi2c_init(void)
 static int __maybe_unused ti_i2c_eeprom_get(int bus_addr, int dev_addr,
 					    u32 header, u32 size, uint8_t *ep)
 {
-	u32 hdr_read = 0xdeadbeef;
 	int rc;
 
 #if CONFIG_IS_ENABLED(DM_I2C)
@@ -113,10 +112,10 @@ static int __maybe_unused ti_i2c_eeprom_get(int bus_addr, int dev_addr,
 	 * We must allow for fall through to check the data if 2 byte
 	 * addressing works
 	 */
-	(void)dm_i2c_read(dev, 0, (uint8_t *)&hdr_read, 4);
+	(void)dm_i2c_read(dev, 0, ep, size);
 
 	/* Corrupted data??? */
-	if (hdr_read != header) {
+	if (*((u32 *)ep) != header) {
 		/*
 		 * read the eeprom header using i2c again, but use only a
 		 * 2 byte address (some newer boards need this..)
@@ -125,16 +124,12 @@ static int __maybe_unused ti_i2c_eeprom_get(int bus_addr, int dev_addr,
 		if (rc)
 			return rc;
 
-		rc = dm_i2c_read(dev, 0, (uint8_t *)&hdr_read, 4);
+		rc = dm_i2c_read(dev, 0, ep, size);
 		if (rc)
 			return rc;
 	}
-	if (hdr_read != header)
+	if (*((u32 *)ep) != header)
 		return -1;
-
-	rc = dm_i2c_read(dev, 0, ep, size);
-	if (rc)
-		return rc;
 #else
 	u32 byte;
 
@@ -154,26 +149,21 @@ static int __maybe_unused ti_i2c_eeprom_get(int bus_addr, int dev_addr,
 	 * We must allow for fall through to check the data if 2 byte
 	 * addressing works
 	 */
-	(void)i2c_read(dev_addr, 0x0, byte, (uint8_t *)&hdr_read, 4);
+	(void)i2c_read(dev_addr, 0x0, byte, ep, size);
 
 	/* Corrupted data??? */
-	if (hdr_read != header) {
+	if (*((u32 *)ep) != header) {
 		/*
 		 * read the eeprom header using i2c again, but use only a
 		 * 2 byte address (some newer boards need this..)
 		 */
 		byte = 2;
-		rc = i2c_read(dev_addr, 0x0, byte, (uint8_t *)&hdr_read,
-			      4);
+		rc = i2c_read(dev_addr, 0x0, byte, ep, size);
 		if (rc)
 			return rc;
 	}
-	if (hdr_read != header)
+	if (*((u32 *)ep) != header)
 		return -1;
-
-	rc = i2c_read(dev_addr, 0x0, byte, ep, size);
-	if (rc)
-		return rc;
 #endif
 	return 0;
 }
-- 
2.26.2