[PATCH 5.1 079/128] mtd: spi-nor: intel-spi: Avoid crossing 4K address boundary on read/write

[Greg Kroah-Hartman]

From: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>

commit 2b75ebeea6f4937d4d05ec4982c471cef9a29b7f upstream.

It was observed that reads crossing 4K address boundary are failing.

This limitation is mentioned in Intel documents:

Intel(R) 9 Series Chipset Family Platform Controller Hub (PCH) Datasheet:

"5.26.3 Flash Access
Program Register Access:
* Program Register Accesses are not allowed to cross a 4 KB boundary..."

Enhanced Serial Peripheral Interface (eSPI)
Interface Base Specification (for Client and Server Platforms):

"5.1.4 Address
For other memory transactions, the address may start or end at any byte
boundary. However, the address and payload length combination must not
cross the naturally aligned address boundary of the corresponding Maximum
Payload Size. It must not cross a 4 KB address boundary."

Avoid this by splitting an operation crossing the boundary into two
operations.

Fixes: 8afda8b26d01 ("spi-nor: Add support for Intel SPI serial flash controller")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Romain Porte <romain.porte@xxxxxxxxx>
Tested-by: Pascal Fabreges <pascal.fabreges@xxxxxxxxx>
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>
Reviewed-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxxxxx>
Acked-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/mtd/spi-nor/intel-spi.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/drivers/mtd/spi-nor/intel-spi.c
+++ b/drivers/mtd/spi-nor/intel-spi.c
@@ -632,6 +632,10 @@ static ssize_t intel_spi_read(struct spi
 	while (len > 0) {
 		block_size = min_t(size_t, len, INTEL_SPI_FIFO_SZ);
 
+		/* Read cannot cross 4K boundary */
+		block_size = min_t(loff_t, from + block_size,
+				   round_up(from + 1, SZ_4K)) - from;
+
 		writel(from, ispi->base + FADDR);
 
 		val = readl(ispi->base + HSFSTS_CTL);
@@ -685,6 +689,10 @@ static ssize_t intel_spi_write(struct sp
 	while (len > 0) {
 		block_size = min_t(size_t, len, INTEL_SPI_FIFO_SZ);
 
+		/* Write cannot cross 4K boundary */
+		block_size = min_t(loff_t, to + block_size,
+				   round_up(to + 1, SZ_4K)) - to;
+
 		writel(to, ispi->base + FADDR);
 
 		val = readl(ispi->base + HSFSTS_CTL);