[SRU][Artful][PATCH 1/2] mfd: lpc_ich: Do not touch SPI-NOR write protection bit on Haswell/Broadwell

[Joseph Salisbury]

From: Mika Westerberg <mika.westerberg at linux.intel.com>

BugLink: http://bugs.launchpad.net/bugs/1742696

At least on Lenovo Thinkpad Yoga, the BIOS seems to monitor the SPI-NOR
write protection bit and if it is flipped to read/write it assumes the
BIOS configuration was changed on next reboot. It then, for unknown
reasons, resets the BIOS settings back to default.

We can prevent this by just leaving the write protection bit intact and
let the SPI-NOR driver know whether the device is writable or not. In
case of this particular Lenovo the SPI-NOR flash will be exposed as
read-only.

Fixes: ff00d7a32a1b ("mfd: lpc_ich: Add support for SPI serial flash host controller")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=195951
Reported-by: Abdó Roig-Marange <abdo.roig at gmail.com>
Signed-off-by: Mika Westerberg <mika.westerberg at linux.intel.com>
Signed-off-by: Lee Jones <lee.jones at linaro.org>
(cherry picked from commit d9018976cdb6eefc62a7ba79a405f6c9661b08a7)
Signed-off-by: Joseph Salisbury <joseph.salisbury at canonical.com>
---
 drivers/mfd/lpc_ich.c | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/drivers/mfd/lpc_ich.c b/drivers/mfd/lpc_ich.c
index 773f155..450ae36 100644
--- a/drivers/mfd/lpc_ich.c
+++ b/drivers/mfd/lpc_ich.c
@@ -1119,17 +1119,7 @@ static int lpc_ich_init_spi(struct pci_dev *dev)
 			res->start = spi_base + SPIBASE_LPT;
 			res->end = res->start + SPIBASE_LPT_SZ - 1;
 
-			/*
-			 * Try to make the flash chip writeable now by
-			 * setting BCR_WPD. It it fails we tell the driver
-			 * that it can only read the chip.
-			 */
 			pci_read_config_dword(dev, BCR, &bcr);
-			if (!(bcr & BCR_WPD)) {
-				bcr |= BCR_WPD;
-				pci_write_config_dword(dev, BCR, bcr);
-				pci_read_config_dword(dev, BCR, &bcr);
-			}
 			info->writeable = !!(bcr & BCR_WPD);
 		}
 		break;
-- 
2.7.4