[RFC PATCH 3/6] spi: bcm53xx: Implement the spi_mem interface

[Boris Brezillon <boris.brezillon-LDxbnhwyfcJBDgjK7y7TUQ@public.gmane.org>]

From: Boris Brezillon <boris.brezillon-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>

The spi_mem interface is meant to replace the spi_flash_read() one.
Implement the ->exec_op() method so that we can smoothly get rid of the
old interface.

Note that the current ->flash_read() implementation looks a bit fragile
since it does not take the ->read_opcode passed by the spi-nor layer
into account, which means if might not work with all kind of NORs.

Anyway, I left the logic unchanged and added a few extra checks to make
sure we're receiving something that looks like a NOR read operation.

Signed-off-by: Boris Brezillon <boris.brezillon-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
---
 drivers/spi/spi-bcm53xx.c | 38 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 37 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi-bcm53xx.c b/drivers/spi/spi-bcm53xx.c
index 6e409eabe1c9..c681d432e26c 100644
--- a/drivers/spi/spi-bcm53xx.c
+++ b/drivers/spi/spi-bcm53xx.c
@@ -263,6 +263,40 @@ static int bcm53xxspi_transfer_one(struct spi_master *master,
 	return 0;
 }
 
+static int bcm53xxspi_exec_mem_op(struct spi_mem *mem,
+				  const struct spi_mem_op *op)
+{
+	struct bcm53xxspi *b53spi = spi_master_get_devdata(mem->spi->master);
+	u32 from;
+
+	/*
+	 * FIXME: There's nothing in this driver programming the opcode and
+	 * buswidth to be used when a read is done on the mmio window, but it
+	 * seems to be used to access a SPI NOR device, so restrict access
+	 * access to SPINOR_OP_READ commands.
+	 */
+	if (!op->data.nbytes || op->data.dir != SPI_MEM_DATA_IN ||
+	    op->addr.nbytes != 3 || op->cmd.opcode != 0x3)
+		return -ENOTSUPP;
+
+	from = ((u32)op->addr.buf[0] << 16) | ((u32)op->addr.buf[1] << 8) |
+	       op->addr.buf[2];
+
+	/* Return -ENOTSUPP so that the core can fall back to normal reads. */
+	if (from + op->data.nbytes > BCM53XXSPI_FLASH_WINDOW)
+		return -ENOTSUPP;
+
+	bcm53xxspi_enable_bspi(b53spi);
+	memcpy_fromio(op->data.buf.in, b53spi->mmio_base + from,
+		      op->data.nbytes);
+
+	return 0;
+}
+
+static const struct spi_controller_mem_ops bcm53xxspi_mem_ops = {
+	.exec_op = bcm53xxspi_exec_mem_op,
+};
+
 static int bcm53xxspi_flash_read(struct spi_device *spi,
 				 struct spi_flash_read_message *msg)
 {
@@ -317,8 +351,10 @@ static int bcm53xxspi_bcma_probe(struct bcma_device *core)
 
 	master->dev.of_node = dev->of_node;
 	master->transfer_one = bcm53xxspi_transfer_one;
-	if (b53spi->mmio_base)
+	if (b53spi->mmio_base) {
+		master->mem_ops = &bcm53xxspi_mem_ops;
 		master->spi_flash_read = bcm53xxspi_flash_read;
+	}
 
 	bcma_set_drvdata(core, b53spi);
 
-- 
2.14.1

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