drivers/spi: support cmd opcode deduction for spi_crop_chunk()

spi_crop_chunk() currently supports deducting the command length
when determining maximum payload size in a transaction. Add support
for deducting just the opcode part of the command by replacing
deduct_cmd_len field to generic flags field. The two enums supported
drive the logic within spi_crop_chunk():
  SPI_CNTRLR_DEDUCT_CMD_LEN
  SPI_CNTRLR_DEDUCT_OPCODE_LEN

All existing users of deduct_cmd_len were converted to using the
flags field.

BUG=b:65485690

Change-Id: I771fba684f0ed76ffdc8573aa10f775070edc691
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/23491
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Justin TerAvest <teravest@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/drivers/spi/spi-generic.c

@@ -93,15 +93,24 @@ unsigned int spi_crop_chunk(const struct spi_slave *slave, unsigned int cmd_len,
 {
 	const struct spi_ctrlr *ctrlr = slave->ctrlr;
 	unsigned int ctrlr_max;
+	bool deduct_cmd_len;
+	bool deduct_opcode_len;
 
 	if (!ctrlr)
 		return 0;
 
+	deduct_cmd_len = !!(ctrlr->flags & SPI_CNTRLR_DEDUCT_CMD_LEN);
+	deduct_opcode_len = !!(ctrlr->flags & SPI_CNTRLR_DEDUCT_OPCODE_LEN);
 	ctrlr_max = ctrlr->max_xfer_size;
 
 	assert (ctrlr_max != 0);
 
-	if (ctrlr->deduct_cmd_len && (ctrlr_max > cmd_len))
+	/* Assume opcode is always one byte and deduct it from the cmd_len
+	   as the hardware has a separate register for the opcode. */
+	if (deduct_opcode_len)
+		cmd_len--;
+
+	if (deduct_cmd_len && (ctrlr_max > cmd_len))
 		ctrlr_max -= cmd_len;
 
 	return min(ctrlr_max, buf_len);

src/include/spi-generic.h

@@ -97,6 +97,17 @@ struct spi_cfg {
 
 struct spi_flash;
 
+enum {
+	/* Deduct the command length from the spi_crop_chunk() calculation for
+	   sizing a transaction. */
+	SPI_CNTRLR_DEDUCT_CMD_LEN = 1 << 0,
+	/* Remove the opcode size from the command length used in the
+	   spi_crop_chunk() calculation. Controllers which have a dedicated
+	   register for the command byte would set this flag which would
+	   allow the use of the maximum transfer size. */
+	SPI_CNTRLR_DEDUCT_OPCODE_LEN = 1 << 1,
+};
+
 /*-----------------------------------------------------------------------
  * Representation of a SPI controller.
  *
@@ -108,8 +119,7 @@ struct spi_flash;
  * max_xfer_size:	Maximum transfer size supported by the controller
  *			(0 = invalid,
  *			 SPI_CTRLR_DEFAULT_MAX_XFER_SIZE = unlimited)
- * deduct_cmd_len:	Whether cmd_len should be deducted from max_xfer_size
- *			when calculating max_data_size
+ * flags:		See SPI_CNTRLR_* enums above.
  *
  * Following member is provided by specialized SPI controllers that are
  * actually SPI flash controllers.
@@ -127,7 +137,7 @@ struct spi_ctrlr {
 	int (*xfer_vector)(const struct spi_slave *slave,
 			struct spi_op vectors[], size_t count);
 	uint32_t max_xfer_size;
-	bool deduct_cmd_len;
+	uint32_t flags;
 	int (*flash_probe)(const struct spi_slave *slave,
 				struct spi_flash *flash);
 	int (*flash_protect)(const struct spi_flash *flash,

src/soc/amd/stoneyridge/spi.c

@@ -193,7 +193,7 @@ static const struct spi_ctrlr spi_ctrlr = {
 	.xfer = spi_ctrlr_xfer,
 	.xfer_vector = spi_xfer_two_vectors,
 	.max_xfer_size = SPI_FIFO_DEPTH,
-	.deduct_cmd_len = true,
+	.flags = SPI_CNTRLR_DEDUCT_CMD_LEN,
 };
 
 const struct spi_ctrlr_buses spi_ctrlr_bus_map[] = {

src/soc/intel/quark/spi.c

@@ -290,7 +290,6 @@ BOOT_STATE_INIT_ENTRY(BS_DEV_INIT, BS_ON_ENTRY, spi_init_cb, NULL);
 const struct spi_ctrlr spi_driver = {
 	.xfer = xfer,
 	.max_xfer_size = 64,
-	.deduct_cmd_len = false,
 };
 
 const struct spi_ctrlr_buses spi_ctrlr_bus_map[] = {

src/southbridge/amd/agesa/hudson/spi.c

@@ -164,7 +164,7 @@ static const struct spi_ctrlr spi_ctrlr = {
 	.xfer = spi_ctrlr_xfer,
 	.xfer_vector = spi_xfer_two_vectors,
 	.max_xfer_size = AMD_SB_SPI_TX_LEN,
-	.deduct_cmd_len = true,
+	.flags = SPI_CNTRLR_DEDUCT_CMD_LEN,
 };
 
 const struct spi_ctrlr_buses spi_ctrlr_bus_map[] = {

src/southbridge/amd/cimx/sb800/spi.c

@@ -155,7 +155,7 @@ static const struct spi_ctrlr spi_ctrlr = {
 	.xfer = spi_ctrlr_xfer,
 	.xfer_vector = spi_xfer_two_vectors,
 	.max_xfer_size = AMD_SB_SPI_TX_LEN,
-	.deduct_cmd_len = true,
+	.flags = SPI_CNTRLR_DEDUCT_CMD_LEN,
 };
 
 const struct spi_ctrlr_buses spi_ctrlr_bus_map[] = {

src/southbridge/amd/sb700/spi.c

@@ -112,7 +112,7 @@ static const struct spi_ctrlr spi_ctrlr = {
 	.xfer = spi_ctrlr_xfer,
 	.xfer_vector = spi_xfer_two_vectors,
 	.max_xfer_size = AMD_SB_SPI_TX_LEN,
-	.deduct_cmd_len = true,
+	.flags = SPI_CNTRLR_DEDUCT_CMD_LEN,
 };
 
 const struct spi_ctrlr_buses spi_ctrlr_bus_map[] = {