spi: bcm63xx-hsspi: add support for 1-2-2 read ops

Add support for 1-2-2 read ops by separately calculating the switch from
single-bit to multi-bit, and then switching within the prepend data.

This allows us to support single-bit write followed by multi-bit write
followed by multi-bit read, and we do not need to reject 1-2-2 read
operations anymore.

Tested on BCM963268BU_P300 with custom fixup to allow 1-2-2 on the
non-SDFP capable s25fl129p1 attached (which it actually supports):

root@OpenWrt:~# cat /sys/kernel/debug/spi-nor/spi1.0/params
name            s25fl129p1
id              01 20 18 4d 01 01
size            16.0 MiB
write size      1
page size       256
address nbytes  3
flags           HAS_16BIT_SR | NO_READ_CR

opcodes
 read           0xbb
  dummy cycles  4
 erase          0xd8
 program        0x02
 8D extension   none

protocols
 read           1S-2S-2S
 write          1S-1S-1S
 register       1S-1S-1S

Reading from flash is still working as expected:

[    1.070000] parser_imagetag: rootfs: CFE image tag found at 0x0 with version 6, board type 963168VX
[    1.080000] parser_imagetag: Partition 0 is rootfs offset 100 and length 665000
[    1.090000] parser_imagetag: Partition 1 is kernel offset 665100 and length 136fa1
[    1.100000] parser_imagetag: Spare partition is offset 7b0000 and length 30000

Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Acked-by: William Zhang <william.zhang@broadcom.com>
Tested-by: David Regan <dregan@broadcom.com>
Link: https://patch.msgid.link/20251217211026.173946-1-jonas.gorski@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: KanjiMonster

drivers/spi/spi-bcm63xx-hsspi.c

@@ -142,6 +142,7 @@ struct bcm63xx_hsspi {
 	u32 wait_mode;
 	u32 xfer_mode;
 	u32 prepend_cnt;
+	u32 md_start;
 	u8 *prepend_buf;
 };
 
@@ -268,18 +269,20 @@ static bool bcm63xx_prepare_prepend_transfer(struct spi_controller *host,
 {
 
 	struct bcm63xx_hsspi *bs = spi_controller_get_devdata(host);
-	bool tx_only = false;
+	bool tx_only = false, multidata = false;
 	struct spi_transfer *t;
 
 	/*
 	 * Multiple transfers within a message may be combined into one transfer
 	 * to the controller using its prepend feature. A SPI message is prependable
 	 * only if the following are all true:
-	 *   1. One or more half duplex write transfer in single bit mode
-	 *   2. Optional full duplex read/write at the end
-	 *   3. No delay and cs_change between transfers
+	 *   1. One or more half duplex write transfers at the start
+	 *   2. Optional switch from single to dual bit within the write transfers
+	 *   3. Optional full duplex read/write at the end if all single bit
+	 *   4. No delay and cs_change between transfers
 	 */
 	bs->prepend_cnt = 0;
+	bs->md_start = 0;
 	list_for_each_entry(t, &msg->transfers, transfer_list) {
 		if ((spi_delay_to_ns(&t->delay, t) > 0) || t->cs_change) {
 			bcm63xx_prepend_printk_on_checkfail(bs,
@@ -297,39 +300,52 @@ static bool bcm63xx_prepare_prepend_transfer(struct spi_controller *host,
 				return false;
 			}
 
-			if (t->tx_nbits > SPI_NBITS_SINGLE &&
-				!list_is_last(&t->transfer_list, &msg->transfers)) {
+			if (t->tx_nbits == SPI_NBITS_SINGLE &&
+			    !list_is_last(&t->transfer_list, &msg->transfers) &&
+			    multidata) {
 				bcm63xx_prepend_printk_on_checkfail(bs,
-					 "multi-bit prepend buf not supported!\n");
+					 "single-bit after multi-bit not supported!\n");
 				return false;
 			}
 
-			if (t->tx_nbits == SPI_NBITS_SINGLE) {
-				memcpy(bs->prepend_buf + bs->prepend_cnt, t->tx_buf, t->len);
-				bs->prepend_cnt += t->len;
-			}
+			if (t->tx_nbits > SPI_NBITS_SINGLE)
+				multidata = true;
+
+			memcpy(bs->prepend_buf + bs->prepend_cnt, t->tx_buf, t->len);
+			bs->prepend_cnt += t->len;
+
+			if (t->tx_nbits == SPI_NBITS_SINGLE)
+				bs->md_start += t->len;
+
 		} else {
 			if (!list_is_last(&t->transfer_list, &msg->transfers)) {
 				bcm63xx_prepend_printk_on_checkfail(bs,
 					 "rx/tx_rx transfer not supported when it is not last one!\n");
 				return false;
 			}
+
+			if (t->rx_buf && t->rx_nbits == SPI_NBITS_SINGLE &&
+			    multidata) {
+				bcm63xx_prepend_printk_on_checkfail(bs,
+					 "single-bit after multi-bit not supported!\n");
+				return false;
+			}
 		}
 
 		if (list_is_last(&t->transfer_list, &msg->transfers)) {
 			memcpy(t_prepend, t, sizeof(struct spi_transfer));
 
-			if (tx_only && t->tx_nbits == SPI_NBITS_SINGLE) {
+			if (tx_only) {
 				/*
-				 * if the last one is also a single bit tx only transfer, merge
+				 * if the last one is also a tx only transfer, merge
 				 * all of them into one single tx transfer
 				 */
 				t_prepend->len = bs->prepend_cnt;
 				t_prepend->tx_buf = bs->prepend_buf;
 				bs->prepend_cnt = 0;
 			} else {
 				/*
-				 * if the last one is not a tx only transfer or dual tx xfer, all
+				 * if the last one is not a tx only transfer, all
 				 * the previous transfers are sent through prepend bytes and
 				 * make sure it does not exceed the max prepend len
 				 */
@@ -339,6 +355,15 @@ static bool bcm63xx_prepare_prepend_transfer(struct spi_controller *host,
 					return false;
 				}
 			}
+			/*
+			 * If switching from single-bit to multi-bit, make sure
+			 * the start offset does not exceed the maximum
+			 */
+			if (multidata && bs->md_start > HSSPI_MAX_PREPEND_LEN) {
+				bcm63xx_prepend_printk_on_checkfail(bs,
+					"exceed max multi-bit offset, abort prepending transfers!\n");
+				return false;
+			}
 		}
 	}
 
@@ -381,11 +406,11 @@ static int bcm63xx_hsspi_do_prepend_txrx(struct spi_device *spi,
 
 		if (t->rx_nbits == SPI_NBITS_DUAL) {
 			reg |= 1 << MODE_CTRL_MULTIDATA_RD_SIZE_SHIFT;
-			reg |= bs->prepend_cnt << MODE_CTRL_MULTIDATA_RD_STRT_SHIFT;
+			reg |= bs->md_start << MODE_CTRL_MULTIDATA_RD_STRT_SHIFT;
 		}
 		if (t->tx_nbits == SPI_NBITS_DUAL) {
 			reg |= 1 << MODE_CTRL_MULTIDATA_WR_SIZE_SHIFT;
-			reg |= bs->prepend_cnt << MODE_CTRL_MULTIDATA_WR_STRT_SHIFT;
+			reg |= bs->md_start << MODE_CTRL_MULTIDATA_WR_STRT_SHIFT;
 		}
 	}
 
@@ -692,13 +717,6 @@ static bool bcm63xx_hsspi_mem_supports_op(struct spi_mem *mem,
 	if (!spi_mem_default_supports_op(mem, op))
 		return false;
 
-	/* Controller doesn't support spi mem dual io mode */
-	if ((op->cmd.opcode == SPINOR_OP_READ_1_2_2) ||
-		(op->cmd.opcode == SPINOR_OP_READ_1_2_2_4B) ||
-		(op->cmd.opcode == SPINOR_OP_READ_1_2_2_DTR) ||
-		(op->cmd.opcode == SPINOR_OP_READ_1_2_2_DTR_4B))
-		return false;
-
 	return true;
 }