drivers/spi/spi_flash: assume spi_flash read callback exists

spi_flash_erase() and spi_flash_write() already assume their
respective callbacks are supplied in the spi_flash_ops object.
Make the same assumption in spi_flash_read(). In order to do this
the spi_flash_ops objects from the drivers need to reference the
the previously used fallback read command, spi_flash_read_chunked().
This function is made global and renamed to spi_flash_cmd_read() for
consistency.

By doing this further dead code elimination can be achieved when the
spi flash drivers aren't included in the build.

A Hatch Chrome OS build achieves a further text segment reduction of
0.5KiB in verstage, romstage, and ramstage.

Change-Id: I7fee55e6ffc1983657c3adde025a0e8c9d12ca23
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/38366
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/drivers/spi/adesto.c

@@ -149,6 +149,7 @@ static const struct adesto_spi_flash_params adesto_spi_flash_table[] = {
 };
 
 static const struct spi_flash_ops spi_flash_ops = {
+	.read = spi_flash_cmd_read,
 	.write = spi_flash_cmd_write_page_program,
 	.erase = spi_flash_cmd_erase,
 };

src/drivers/spi/amic.c

@@ -120,6 +120,7 @@ static const struct amic_spi_flash_params amic_spi_flash_table[] = {
 };
 
 static const struct spi_flash_ops spi_flash_ops = {
+	.read = spi_flash_cmd_read,
 	.write = spi_flash_cmd_write_page_program,
 	.erase = spi_flash_cmd_erase,
 };

src/drivers/spi/atmel.c

@@ -104,6 +104,7 @@ static const struct atmel_spi_flash_params atmel_spi_flash_table[] = {
 };
 
 static const struct spi_flash_ops spi_flash_ops = {
+	.read = spi_flash_cmd_read,
 	.write = spi_flash_cmd_write_page_program,
 	.erase = spi_flash_cmd_erase,
 };

src/drivers/spi/eon.c

@@ -236,6 +236,7 @@ static const struct eon_spi_flash_params eon_spi_flash_table[] = {
 };
 
 static const struct spi_flash_ops spi_flash_ops = {
+	.read = spi_flash_cmd_read,
 	.write = spi_flash_cmd_write_page_program,
 	.erase = spi_flash_cmd_erase,
 	.status = spi_flash_cmd_status,

src/drivers/spi/gigadevice.c

@@ -165,6 +165,7 @@ static const struct gigadevice_spi_flash_params gigadevice_spi_flash_table[] = {
 };
 
 static const struct spi_flash_ops spi_flash_ops = {
+	.read = spi_flash_cmd_read,
 	.write = spi_flash_cmd_write_page_program,
 	.erase = spi_flash_cmd_erase,
 	.status = spi_flash_cmd_status,

src/drivers/spi/macronix.c

@@ -201,6 +201,7 @@ static const struct macronix_spi_flash_params macronix_spi_flash_table[] = {
 };
 
 static const struct spi_flash_ops spi_flash_ops = {
+	.read = spi_flash_cmd_read,
 	.write = spi_flash_cmd_write_page_program,
 	.erase = spi_flash_cmd_erase,
 	.status = spi_flash_cmd_status,

src/drivers/spi/spansion.c

@@ -219,6 +219,7 @@ static const struct spansion_spi_flash_params spansion_spi_flash_table[] = {
 };
 
 static const struct spi_flash_ops spi_flash_ops = {
+	.read = spi_flash_cmd_read,
 	.write = spi_flash_cmd_write_page_program,
 	.erase = spi_flash_cmd_erase,
 	.status = spi_flash_cmd_status,

src/drivers/spi/spi_flash.c

@@ -127,7 +127,7 @@ int spi_flash_cmd_write(const struct spi_slave *spi, const u8 *cmd,
 
 /* Perform the read operation honoring spi controller fifo size, reissuing
  * the read command until the full request completed. */
-static int spi_flash_read_chunked(const struct spi_flash *flash, u32 offset,
+int spi_flash_cmd_read(const struct spi_flash *flash, u32 offset,
 				  size_t len, void *buf)
 {
 	u8 cmd[5];
@@ -465,10 +465,7 @@ int spi_flash_probe(unsigned int bus, unsigned int cs, struct spi_flash *flash)
 int spi_flash_read(const struct spi_flash *flash, u32 offset, size_t len,
 		void *buf)
 {
-	if (flash->ops->read)
-		return flash->ops->read(flash, offset, len, buf);
-
-	return spi_flash_read_chunked(flash, offset, len, buf);
+	return flash->ops->read(flash, offset, len, buf);
 }
 
 int spi_flash_write(const struct spi_flash *flash, u32 offset, size_t len,

src/drivers/spi/spi_flash_internal.h

@@ -66,6 +66,9 @@ int spi_flash_cmd_status(const struct spi_flash *flash, u8 *reg);
 int spi_flash_cmd_write_page_program(const struct spi_flash *flash, u32 offset,
 				size_t len, const void *buf);
 
+/* Read len bytes into buf at offset. */
+int spi_flash_cmd_read(const struct spi_flash *flash, u32 offset, size_t len, void *buf);
+
 /* Manufacturer-specific probe functions */
 int spi_flash_probe_spansion(const struct spi_slave *spi, u8 *idcode,
 			     struct spi_flash *flash);

src/drivers/spi/sst.c

@@ -55,12 +55,14 @@ static int sst_write_ai(const struct spi_flash *flash, u32 offset, size_t len,
 			const void *buf);
 
 static const struct spi_flash_ops spi_flash_ops_write_ai = {
+	.read = spi_flash_cmd_read,
 	.write = sst_write_ai,
 	.erase = spi_flash_cmd_erase,
 	.status = spi_flash_cmd_status,
 };
 
 static const struct spi_flash_ops spi_flash_ops_write_256 = {
+	.read = spi_flash_cmd_read,
 	.write = spi_flash_cmd_write_page_program,
 	.erase = spi_flash_cmd_erase,
 	.status = spi_flash_cmd_status,

src/drivers/spi/stmicro.c

@@ -285,6 +285,7 @@ static const struct stmicro_spi_flash_params stmicro_spi_flash_table[] = {
 };
 
 static const struct spi_flash_ops spi_flash_ops = {
+	.read = spi_flash_cmd_read,
 	.write = spi_flash_cmd_write_page_program,
 	.erase = spi_flash_cmd_erase,
 };

src/drivers/spi/winbond.c

@@ -611,6 +611,7 @@ winbond_set_write_protection(const struct spi_flash *flash,
 }
 
 static const struct spi_flash_ops spi_flash_ops = {
+	.read = spi_flash_cmd_read,
 	.write = spi_flash_cmd_write_page_program,
 	.erase = spi_flash_cmd_erase,
 	.status = spi_flash_cmd_status,