mfd: lpc_ich: Do not touch SPI-NOR write protection bit on Haswell/Broadwell

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 <[email protected]>

Signed-off-by Mika Westerberg <[email protected]>

---
 drivers/mfd/lpc_ich.c | 10 ----------
 1 file changed, 10 deletions(-)

drivers/mfd/lpc_ich.c +0 -10

index 773f1554d2f9..450ae36645aa 100644
@@ -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;