[PATCH 2/3] spi: spi-ti-qspi: support large flash devices

[Jean Pihet <jean.pihet@xxxxxxxxxxxxxx>]

The TI QSPI IP has limitations:
- the MMIO region is 64MB in size
- in non-MMIO mode, the transfer can handle 4096 words max.

Add support for bigger devices.
Use MMIO and DMA transfers below the 64MB boundary, use
software generated transfers above.

Signed-off-by: Jean Pihet <jean.pihet@xxxxxxxxxxxxxx>
Cc: Ryan Barnett <ryan.barnett@xxxxxxxxxxxxxxxxxxx>
Cc: Conrad Ratschan <conrad.ratschan@xxxxxxxxxxxxxxxxxxx>
Cc: Arnout Vandecappelle <arnout.vandecappelle@xxxxxxxxxxxxx>
---
 drivers/spi/spi-ti-qspi.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/drivers/spi/spi-ti-qspi.c b/drivers/spi/spi-ti-qspi.c
index a18835128ad0..aee4709d105e 100644
--- a/drivers/spi/spi-ti-qspi.c
+++ b/drivers/spi/spi-ti-qspi.c
@@ -522,6 +522,33 @@ static void ti_qspi_setup_mmap_read(struct spi_device *spi, u8 opcode,
 		      QSPI_SPI_SETUP_REG(spi->chip_select));
 }
 
+static int ti_qspi_adjust_op_size(struct spi_mem *mem, struct spi_mem_op *op)
+{
+	struct ti_qspi *qspi = spi_controller_get_devdata(mem->spi->master);
+	size_t max_len;
+
+	if (op->data.dir == SPI_MEM_DATA_IN) {
+		if (op->addr.val < qspi->mmap_size) {
+			/* Limit MMIO to the mmaped region */
+			if (op->addr.val + op->data.nbytes > qspi->mmap_size) {
+				max_len = qspi->mmap_size - op->addr.val;
+				op->data.nbytes = min(op->data.nbytes, max_len);
+			}
+		} else {
+			/*
+			 * Use fallback mode (SW generated transfers) above the
+			 * mmaped region.
+			 * Adjust size to comply with the QSPI max frame length.
+			 */
+			max_len = QSPI_FRAME;
+			max_len -= 1 + op->addr.nbytes + op->dummy.nbytes;
+			op->data.nbytes = min(op->data.nbytes, max_len);
+		}
+	}
+
+	return 0;
+}
+
 static int ti_qspi_exec_mem_op(struct spi_mem *mem,
 			       const struct spi_mem_op *op)
 {
@@ -572,6 +599,7 @@ static int ti_qspi_exec_mem_op(struct spi_mem *mem,
 
 static const struct spi_controller_mem_ops ti_qspi_mem_ops = {
 	.exec_op = ti_qspi_exec_mem_op,
+	.adjust_op_size = ti_qspi_adjust_op_size,
 };
 
 static int ti_qspi_start_transfer_one(struct spi_master *master,
-- 
2.23.0