[PATCH] spi: intel: Allow writeable MTD partition with module param

[Jakub Czapiga <czapiga@google.com>]

The MTD device is blocked from writing to the SPI-NOR chip if any region
of it is write-protected, even if "writeable=1" module parameter is set.

Add ability to bypass this behaviour by introducing new module parameter
"ignore_protestion_status" which allows to rely on the write protection
mechanism of SPI-NOR chip itself, which most modern chips (since
the 1990'+) have already implemented.

Any erase/write operations performed on the write-protected section will
be rejected by the chip.

Signed-off-by: Jakub Czapiga <czapiga@google.com>
---
 drivers/spi/spi-intel.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/spi/spi-intel.c b/drivers/spi/spi-intel.c
index 5d5a546c62ea..9b41cf9caa5b 100644
--- a/drivers/spi/spi-intel.c
+++ b/drivers/spi/spi-intel.c
@@ -189,6 +189,11 @@ struct intel_spi_mem_op {
 static bool writeable;
 module_param(writeable, bool, 0);
 MODULE_PARM_DESC(writeable, "Enable write access to SPI flash chip (default=0)");
+static bool ignore_protection_status;
+module_param(ignore_protection_status, bool, 0);
+MODULE_PARAM_DESC(
+	ignore_protection_status,
+	"Do not block SPI flash chip write access even if it is write-protected (default=0)");
 
 static void intel_spi_dump_regs(struct intel_spi *ispi)
 {
@@ -1248,13 +1253,15 @@ static void intel_spi_fill_partition(struct intel_spi *ispi,
 			continue;
 
 		/*
-		 * If any of the regions have protection bits set, make the
-		 * whole partition read-only to be on the safe side.
+		 * If any of the regions have protection bits set and
+		 * the ignore protection status parameter is not set,
+		 * make the whole partition read-only to be on the safe side.
 		 *
 		 * Also if the user did not ask the chip to be writeable
 		 * mask the bit too.
 		 */
-		if (!writeable || intel_spi_is_protected(ispi, base, limit)) {
+		if (!writeable || (!ignore_protection_status &&
+				   intel_spi_is_protected(ispi, base, limit))) {
 			part->mask_flags |= MTD_WRITEABLE;
 			ispi->protected = true;
 		}
-- 
2.50.0.727.gbf7dc18ff4-goog