Re: [PATCH] Module argument to control whether intel-spi-pci attempts to turn the SPI flash chip writeable

Mika Westerberg
2020-08-03T09:57:28Z

Hi,

Sorry for the delay, I was on vacation.

On Fri, Jul 24, 2020 at 06:28:53PM -0300, Daniel Gutson wrote:
> Currently, intel-spi has a module argument that controls whether the driver
> attempts to turn the SPI flash chip writeable. The default value
> is FALSE (don't try to make it writeable).
> However, this flag applies only for a number of devices, coming from the
> platform driver, whereas the devices detected through the PCI driver
> (intel-spi-pci) are not subject to this check since the configuration
> takes place in intel-spi-pci which doesn't have an argument.
>
> That's why I propose this patch to add such argument to intel-spi-pci,
> so the user can control whether the driver tries to make the chip
> writeable or not, being the default FALSE as is the argument of
> intel-spi.
>
> Signed-off-by: Daniel Gutson <daniel.gutson@eclypsium.com>
> ---
> drivers/mtd/spi-nor/controllers/intel-spi-pci.c | 16 +++++++++++-----
> 1 file changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/mtd/spi-nor/controllers/intel-spi-pci.c b/drivers/mtd/spi-nor/controllers/intel-spi-pci.c
> index 81329f680bec..77e57450f166 100644
> --- a/drivers/mtd/spi-nor/controllers/intel-spi-pci.c
> +++ b/drivers/mtd/spi-nor/controllers/intel-spi-pci.c
> @@ -24,6 +24,10 @@ static const struct intel_spi_boardinfo cnl_info = {
> .type = INTEL_SPI_CNL,
> };
>
> +static bool writeable;
> +module_param(writeable, bool, 0);
> +MODULE_PARM_DESC(writeable, "Enable write access to SPI flash chip (default=0)");

I think instead of this we should simply make it so that the driver
never tries to make the chip writable.

> +
> static int intel_spi_pci_probe(struct pci_dev *pdev,
> const struct pci_device_id *id)
> {
> @@ -41,12 +45,14 @@ static int intel_spi_pci_probe(struct pci_dev *pdev,
> if (!info)
> return -ENOMEM;
>
> - /* Try to make the chip read/write */
> - pci_read_config_dword(pdev, BCR, &bcr);
> - if (!(bcr & BCR_WPD)) {
> - bcr |= BCR_WPD;
> - pci_write_config_dword(pdev, BCR, bcr);
> + if (writeable) {
> + /* Try to make the chip read/write */
> pci_read_config_dword(pdev, BCR, &bcr);
> + if (!(bcr & BCR_WPD)) {
> + bcr |= BCR_WPD;
> + pci_write_config_dword(pdev, BCR, bcr);
> + pci_read_config_dword(pdev, BCR, &bcr);
> + }
> }
> info->writeable = !!(bcr & BCR_WPD);

So here we just read the BCR register and then set info->writeable based
on its value.

Then it is up to the BIOS to enable this if it allows writing the flash
chip from the OS side.