realtek_mst_i2c_spi.c: Fix _spi_send_command cb for erasures

Before issuing SPI opcodes into 0x61 the top three BITS of
0x60 need to be carefully crafted. Correctly craft these
in the case of SPI erasures and document this registers
expectations. Clean up remaining debug comments while we
are here.

BUG=b:152558985,b:148745673
BRANCH=none
TEST=flashrom -p realtek_mst_i2c_spi:bus=8 -E  &&
  flashrom -p realtek_mst_i2c_spi:bus=8 -r foo &&
  hexdump -C foo

Change-Id: Ib11ba8f63b11a1c5ebaa68deb7971648de8c2ecd
Signed-off-by: Edward O'Callaghan <quasisec@google.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/41079


Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Sam McNally <sammc@google.com>

realtek_mst_i2c_spi.c

@@ -196,21 +196,55 @@ static int realtek_mst_i2c_spi_send_command(const struct flashctx *flash,
 	int ret = 0;
 
 	if (writecnt > 4 || readcnt > 3 || writecnt == 0) {
-		//msg_perr("%s: Invalid read/write count for send command.\n", __func__);
 		return SPI_GENERIC_ERROR;
 	}
-	//printf("%s: writearr[0]=0x%x\n", __func__, writearr[0]);
 
 	int fd = get_fd_from_context(flash);
 	if (fd < 0)
 		return SPI_GENERIC_ERROR;
 
-	/* First byte of writearr should be the command value, followed by the value to write. */
-	// 0xFF60 = cmd;
+	/* First byte of writearr should be the spi opcode value, followed by the value to write. */
 	writecnt--;
-	uint8_t ctrl_reg_val = (writecnt << 3) | (readcnt << 1) | (2 << 5);
+
+	/**
+	 * Before dispatching a SPI opcode the MCU register 0x60 requires
+	 * the following configuration byte set:
+	 *
+	 *  BIT0      - start [0] , end [1].
+	 *  BITS[1-4] - counts.
+	 *  BITS[5-7] - opcode type.
+	 *
+	 * | bit7 | bit6 | bit5 |
+	 * +------+------+------+
+	 * |  0   |  1   |  0   | ~ JEDEC_RDID,REMS,READ
+	 * |  0   |  1   |  1   | ~ JEDEC_WRSR
+	 * |  1   |  0   |  1   | ~ JEDEC_.. erasures.
+	 */
+	uint8_t ctrl_reg_val = (writecnt << 3) | (readcnt << 1);
+	switch (writearr[0]) {
+	/* WREN isn't a supported somehow? ignore it. */
+	case JEDEC_WREN: return 0;
+	/* WRSR requires BIT6 && BIT5 set. */
+	case JEDEC_WRSR:
+		ctrl_reg_val |= (1 << 5);
+		ctrl_reg_val |= (2 << 5);
+		break;
+	/* Erasures require BIT7 && BIT5 set. */
+	case JEDEC_CE_60:
+	case JEDEC_CE_C7:
+	case JEDEC_BE_52:
+	case JEDEC_BE_D8:
+	case JEDEC_BE_D7:
+	case JEDEC_SE:
+		ctrl_reg_val |= (1 << 5);
+		ctrl_reg_val |= (4 << 5);
+		break;
+	default:
+		/* Otherwise things like RDID,REMS,READ require BIT6 */
+		ctrl_reg_val |= (2 << 5);
+	}
 	ret |= realtek_mst_i2c_spi_write_register(fd, 0x60, ctrl_reg_val);
-	ret |= realtek_mst_i2c_spi_write_register(fd, 0x61, writearr[0]);
+	ret |= realtek_mst_i2c_spi_write_register(fd, 0x61, writearr[0]); /* opcode */
 
 	for (i = 0; i < writecnt; ++i)
 		ret |= realtek_mst_i2c_spi_write_register(fd, 0x64 + i, writearr[i + 1]);
@@ -225,9 +259,6 @@ static int realtek_mst_i2c_spi_send_command(const struct flashctx *flash,
 	for (i = 0; i < readcnt; ++i)
 		ret |= realtek_mst_i2c_spi_read_register(fd, 0x67 + i, &readarr[i]);
 
-	//for (i = 0; i< readcnt; i++)
-	//	printf("DEBUG: readarr[%d]=0x%02x\n", i, readarr[i]);
-
 	return ret;
 }