spi: atmel-quadspi: fix possible MMIO window size overrun

The QSPI controller memory space is limited to 128MB:
0x9000_00000-0x9800_00000/0XD000_0000--0XD800_0000.

There are nor flashes that are bigger in size than the memory size
supported by the controller: Micron MT25QL02G (256 MB).

Check if the address exceeds the MMIO window size. An improvement
would be to add support for regular SPI mode and fall back to it
when the flash memories overrun the controller's memory space.

Fixes: 0e6aae08 ("spi: Add QuadSPI driver for Atmel SAMA5D2")
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20200228155437.1558219-1-tudor.ambarus@microchip.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/atmel-quadspi.c

@@ -149,6 +149,7 @@ struct atmel_qspi {
 	struct clk		*qspick;
 	struct platform_device	*pdev;
 	const struct atmel_qspi_caps *caps;
+	resource_size_t		mmap_size;
 	u32			pending;
 	u32			mr;
 	u32			scr;
@@ -329,6 +330,14 @@ static int atmel_qspi_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
 	u32 sr, offset;
 	int err;
 
+	/*
+	 * Check if the address exceeds the MMIO window size. An improvement
+	 * would be to add support for regular SPI mode and fall back to it
+	 * when the flash memories overrun the controller's memory space.
+	 */
+	if (op->addr.val + op->data.nbytes > aq->mmap_size)
+		return -ENOTSUPP;
+
 	err = atmel_qspi_set_cfg(aq, op, &offset);
 	if (err)
 		return err;
@@ -480,6 +489,8 @@ static int atmel_qspi_probe(struct platform_device *pdev)
 		goto exit;
 	}
 
+	aq->mmap_size = resource_size(res);
+
 	/* Get the peripheral clock */
 	aq->pclk = devm_clk_get(&pdev->dev, "pclk");
 	if (IS_ERR(aq->pclk))