Re: [PATCH 2/3] mfd: lpc_ich: Add support for SPI serial flash host controller

[Mika Westerberg <mika.westerberg@linux.intel.com>]

On Wed, Jun 15, 2016 at 04:38:35PM +0100, Lee Jones wrote:
> On Tue, 14 Jun 2016, Mika Westerberg wrote:
> 
> > Many Intel CPUs including Haswell, Broadwell and Baytrail have SPI serial
> > flash host controller as part of the LPC device. This will populate an MFD
> > cell suitable for the SPI host controller driver if we know that the LPC
> > device has one.
> > 
> > Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
> > ---
> >  drivers/mfd/lpc_ich.c       | 97 +++++++++++++++++++++++++++++++++++++++++++++
> >  include/linux/mfd/lpc_ich.h |  3 ++
> >  2 files changed, 100 insertions(+)
> > 
> > diff --git a/drivers/mfd/lpc_ich.c b/drivers/mfd/lpc_ich.c
> > index bd3aa4578346..39b7731d769a 100644
> > --- a/drivers/mfd/lpc_ich.c
> > +++ b/drivers/mfd/lpc_ich.c
> > @@ -83,6 +83,13 @@
> >  #define ACPIBASE_GCS_OFF	0x3410
> >  #define ACPIBASE_GCS_END	0x3414
> >  
> > +#define SPIBASE_BYT		0x54
> > +#define SPIBASE_BYT_EN		BIT(1)
> > +
> > +#define SPIBASE_LPT		0x3800
> > +#define BCR			0xdc
> > +#define BCR_WPD			BIT(0)
> > +
> >  #define GPIOBASE_ICH0		0x58
> >  #define GPIOCTRL_ICH0		0x5C
> >  #define GPIOBASE_ICH6		0x48
> > @@ -133,6 +140,12 @@ static struct resource gpio_ich_res[] = {
> >  	},
> >  };
> >  
> > +static struct resource intel_spi_res[] = {
> > +	{
> > +		.flags = IORESOURCE_MEM,
> > +	}
> > +};
> > +
> >  static struct mfd_cell lpc_ich_wdt_cell = {
> >  	.name = "iTCO_wdt",
> >  	.num_resources = ARRAY_SIZE(wdt_ich_res),
> > @@ -147,6 +160,14 @@ static struct mfd_cell lpc_ich_gpio_cell = {
> >  	.ignore_resource_conflicts = true,
> >  };
> >  
> > +
> > +static struct mfd_cell lpc_ich_spi_cell = {
> > +	.name = "intel-spi",
> > +	.num_resources = ARRAY_SIZE(intel_spi_res),
> > +	.resources = intel_spi_res,
> > +	.ignore_resource_conflicts = true,
> > +};
> > +
> >  /* chipset related info */
> >  enum lpc_chipsets {
> >  	LPC_ICH = 0,	/* ICH */
> > @@ -493,10 +514,12 @@ static struct lpc_ich_info lpc_chipset_info[] = {
> >  	[LPC_LPT] = {
> >  		.name = "Lynx Point",
> >  		.iTCO_version = 2,
> > +		.spi_type = INTEL_SPI_LPT,
> >  	},
> >  	[LPC_LPT_LP] = {
> >  		.name = "Lynx Point_LP",
> >  		.iTCO_version = 2,
> > +		.spi_type = INTEL_SPI_LPT,
> >  	},
> >  	[LPC_WBG] = {
> >  		.name = "Wellsburg",
> > @@ -510,6 +533,7 @@ static struct lpc_ich_info lpc_chipset_info[] = {
> >  	[LPC_BAYTRAIL] = {
> >  		.name = "Bay Trail SoC",
> >  		.iTCO_version = 3,
> > +		.spi_type = INTEL_SPI_BYT,
> >  	},
> >  	[LPC_COLETO] = {
> >  		.name = "Coleto Creek",
> > @@ -518,10 +542,12 @@ static struct lpc_ich_info lpc_chipset_info[] = {
> >  	[LPC_WPT_LP] = {
> >  		.name = "Wildcat Point_LP",
> >  		.iTCO_version = 2,
> > +		.spi_type = INTEL_SPI_LPT,
> >  	},
> >  	[LPC_BRASWELL] = {
> >  		.name = "Braswell SoC",
> >  		.iTCO_version = 3,
> > +		.spi_type = INTEL_SPI_BYT,
> >  	},
> >  	[LPC_LEWISBURG] = {
> >  		.name = "Lewisburg",
> > @@ -875,6 +901,15 @@ static void lpc_ich_finalize_gpio_cell(struct pci_dev *dev)
> >  	cell->pdata_size = sizeof(struct lpc_ich_info);
> >  }
> >  
> > +static void lpc_ich_finalize_spi_cell(struct pci_dev *dev,
> > +				     struct intel_spi_boardinfo *info)
> > +{
> > +	struct mfd_cell *cell = &lpc_ich_spi_cell;
> > +
> > +	cell->platform_data = info;
> > +	cell->pdata_size = sizeof(*info);
> > +}
> 
> This call doesn't appear to offer anything.  In fact, it looks like it
> adds more lines than is required.

Yeah, it follows what we do with other parts but I can do this in
lpc_ich_init_spi() instead.

> >  /*
> >   * We don't check for resource conflict globally. There are 2 or 3 independent
> >   * GPIO groups and it's enough to have access to one of these to instantiate
> > @@ -1050,6 +1085,62 @@ wdt_done:
> >  	return ret;
> >  }
> >  
> > +static int lpc_ich_init_spi(struct pci_dev *dev)
> > +{
> > +	struct lpc_ich_priv *priv = pci_get_drvdata(dev);
> > +	struct resource *res = &intel_spi_res[0];
> > +	struct intel_spi_boardinfo *info;
> > +	u32 spi_base, rcba, bcr;
> > +
> > +	info = devm_kzalloc(&dev->dev, sizeof(*info), GFP_KERNEL);
> > +	if (!info)
> > +		return -ENOMEM;
> > +
> > +	info->type = lpc_chipset_info[priv->chipset].spi_type;
> > +
> > +	switch (lpc_chipset_info[priv->chipset].spi_type) {
> 
> The type now exists in info->type.  I suggest you use that here
> instead.

OK

> > +	case INTEL_SPI_BYT:
> > +		pci_read_config_dword(dev, SPIBASE_BYT, &spi_base);
> > +		if (spi_base & SPIBASE_BYT_EN) {
> > +			res->start = spi_base &= 0xfffffe00;
> > +			res->end = res->start + 512 - 1;
> 
> Define all of these magic numbers.

OK

> > +		}
> > +		break;
> > +
> > +	case INTEL_SPI_LPT:
> > +		pci_read_config_dword(dev, RCBABASE, &rcba);
> > +		if (rcba & 1) {
> > +			spi_base = rcba & 0xfffffe00;
> > +			res->start = spi_base + SPIBASE_LPT;
> > +			res->end = res->start + 512 - 1;
> 
> And here.

OK

> > +			/*
> > +			 * 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);
> 
> I'd prefer if you didn't do that here.  In fact, is there any
> technical reason why you can't move the entirety of this function into
> the SPI NOR driver?

Unfortunately, I was not able to figure better way. With the exception
of Baytrail (BYT) these bits are part of the PCI device and you need to
access them using PCI config cycles. It gets worse with Broxton (BXT)
where this all is part of "hidden" P2SB PCI device.

I thought about adding a callback which can be used to toggle the bit
but that would require passing pointer to the PCI device (and for
Broxton, I don't know what we would pass, to be honest).

> > +		}
> > +		break;
> > +
> > +	default:
> > +		return -EINVAL;
> > +	}
> > +
> > +	if (!res->start)
> > +		return -ENODEV;
> > +
> > +	lpc_ich_finalize_spi_cell(dev, info);
> > +	return mfd_add_devices(&dev->dev, -1, &lpc_ich_spi_cell, 1, NULL, 0,
> 
> Use the includes provided.  Look at other drivers for examples.

Okay.