4BA: Support for 4-bytes addressing via Extended Address Register

On some flash chips data with addresses more than 24-bit field
can address may be accessed by using Extended Address Register.
The register has 1-byte size and stores high byte of 32-bit address.
Then flash can be read from 3-bytes addressing mode with writing
high byte of address to this Register. By using this way we have
access to full memory of a chip. Some chips may support this method
only.

This patch provides code use Extended Address Register.

Patched files
-------------
chipdrivers.h
+ added functions declarations for spi4ba.c

flash.h
+ feature definitions added

flashrom.c
+ modified switch to 4-bytes addressing to support extended address register

spi4ba.h
+ definitions for 4-bytes addressing JEDEC commands
+ functions declarations from spi4ba.c (same as in chipdrivers.h, just to see)

spi4ba.c
+ functions for write Extended Address Register
+ functions for read/write/erase with Extended Address Register

Change-Id: I09a8aa11de2ca14901f142c67c83c4fa0def4e27
Signed-off-by: Boris Baykov <dev@borisbaykov.com>, Russia, Jan 2014
[clg: ported from
      https://www.flashrom.org/pipermail/flashrom/2015-January/013200.html ]
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-on: https://review.coreboot.org/20507
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>

1 files changed, 4 insertions, 0 deletions

diff --git a/flashrom.c b/flashrom.c
index 8e2243466..3adc3c00e 100644
--- a/flashrom.c
+++ b/flashrom.c
@@ -2229,6 +2229,10 @@ int prepare_flash_access(struct flashctx *const flash,
 		if (flash->chip->feature_bits & FEATURE_4BA_ONLY) {
 			msg_cdbg("Flash chip is already in 4-bytes addressing mode.\n");
 		}
+		/* Do not switch to 4-Bytes Addressing mode if using Extended Address Register */
+		else if(flash->chip->feature_bits & FEATURE_4BA_EXTENDED_ADDR_REG) {
+			msg_cdbg("Using 4-bytes addressing with extended address register.\n");
+		}
 		/* Go to 4-Bytes Addressing mode */
 		else {
 			if (!flash->chip->four_bytes_addr_funcs.enter_4ba) {