linux-kernel - Re: [PATCH] mfd: lpc_ich: Do not touch SPI-NOR write protection bit on Haswell/Broadwell

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Date:   Tue, 8 Aug 2017 08:29:52 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, Peter Tyser <ptyser@...-inc.com>,
        abdo.roig@...il.com
Subject: Re: [PATCH] mfd: lpc_ich: Do not touch SPI-NOR write protection bit
 on Haswell/Broadwell

On Fri, 28 Jul 2017, Mika Westerberg wrote:

> 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@...il.com>
> Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> ---
>  drivers/mfd/lpc_ich.c | 10 ----------
>  1 file changed, 10 deletions(-)

Applied, thanks.

> diff --git a/drivers/mfd/lpc_ich.c b/drivers/mfd/lpc_ich.c
> index 773f1554d2f9..450ae36645aa 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;

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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