Re: [PATCH v6 18/19] platform/x86: intel_pmc_ipc: Convert to MFD

[Lee Jones]

On Wed, 26 Feb 2020, Mika Westerberg wrote:

> On Wed, Feb 26, 2020 at 08:47:49AM +0000, Lee Jones wrote:
> > On Mon, 17 Feb 2020, Mika Westerberg wrote:
> > 
> > > This driver only creates a bunch of platform devices sharing resources
> > > belonging to the PMC device. This is pretty much what MFD subsystem is
> > > for so move the driver there, renaming it to intel_pmc_bxt.c which
> > > should be more clear what it is.
> > > 
> > > MFD subsystem provides nice helper APIs for subdevice creation so
> > > convert the driver to use those. Unfortunately the ACPI device includes
> > > separate resources for most of the subdevices so we cannot simply call
> > > mfd_add_devices() to create all of them but instead we need to call it
> > > separately for each device.
> > > 
> > > The new MFD driver continues to expose two sysfs attributes that allow
> > > userspace to send IPC commands to the PMC/SCU to avoid breaking any
> > > existing applications that may use these. Generally this is bad idea so
> > > document this in the ABI documentation.
> > > 
> > > Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
> > > Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> > > ---
> > >  .../ABI/obsolete/sysfs-driver-intel_pmc_bxt   |  22 +
> > >  arch/x86/include/asm/intel_pmc_ipc.h          |  47 --
> > >  arch/x86/include/asm/intel_telemetry.h        |   1 +
> > >  drivers/mfd/Kconfig                           |  16 +-
> > >  drivers/mfd/Makefile                          |   1 +
> > >  drivers/mfd/intel_pmc_bxt.c                   | 489 +++++++++++++
> > >  drivers/platform/x86/Kconfig                  |  16 +-
> > >  drivers/platform/x86/Makefile                 |   1 -
> > >  drivers/platform/x86/intel_pmc_ipc.c          | 645 ------------------
> > >  .../platform/x86/intel_telemetry_debugfs.c    |  12 +-
> > >  drivers/platform/x86/intel_telemetry_pltdrv.c |   2 +
> > >  drivers/usb/typec/tcpm/Kconfig                |   2 +-
> > >  include/linux/mfd/intel_pmc_bxt.h             |  21 +
> > >  13 files changed, 565 insertions(+), 710 deletions(-)
> > >  create mode 100644 Documentation/ABI/obsolete/sysfs-driver-intel_pmc_bxt
> > >  delete mode 100644 arch/x86/include/asm/intel_pmc_ipc.h
> > >  create mode 100644 drivers/mfd/intel_pmc_bxt.c
> > >  delete mode 100644 drivers/platform/x86/intel_pmc_ipc.c
> > >  create mode 100644 include/linux/mfd/intel_pmc_bxt.h
> > 
> > [...]

[...]

> > > +struct intel_pmc_dev {
> > > +	struct device *dev;
> > > +	struct intel_scu_ipc_dev *scu;
> > > +
> > > +	struct mfd_cell cells[PMC_TELEM + 1];
> > 
> > Nicer to add a "PMC_DEVICE_MAX" enum and use that.
> > 
> > Why do these even need to be in here?
> 
> They need to be here because we need to fill them in dynamically based
> on the resources we get from the ACPI device.

Why can't you do that with statically defined structs?

HINT: You can.

> > I would normally suggest creating a cell per device.
> 
> You mean 
> 
> struct intel_pmc_dev {
> 	...
> 	struct mfd_cell tco_cell;
> 	struct mfd_cell punit_cell;
> 	...
> 
> right? Sure no problem.

No.  We don't usually put them in device data at all.

I mean:

static struct mfd_cell tco_cell[] = {
        {      }
};

static struct mfd_cell tco_cell[] = {
        {      }
};

[...]

> > > +static const struct mfd_cell tco = {
> > > +	.name = TCO_DEVICE_NAME,
> > 
> > Use proper string please.
> > 
> > > +	.ignore_resource_conflicts = true,
> > 
> > Why not add tco_pdata here?
> 
> Because we need to pass it the private PMC pointer that is filled later
> on. It is being used by the iTCO_wdt .update_no_reboot_bit() callback as
> its private data.

Just drop the const.

> > > +};
> > > +
> > > +static const struct resource telem_res[] = {
> > > +	DEFINE_RES_MEM(TELEM_PUNIT_SSRAM_OFFSET, TELEM_SSRAM_SIZE),
> > > +	DEFINE_RES_MEM(TELEM_PMC_SSRAM_OFFSET, TELEM_SSRAM_SIZE),
> > > +};
> > > +
> > > +static const struct mfd_cell telem = {
> > > +	.name = TELEMETRY_DEVICE_NAME,
> > 
> > Use proper string please.
> 
> Okay.
> 
> > > +	.resources = telem_res,
> > > +	.num_resources = ARRAY_SIZE(telem_res),
> > > +};
> > > +
> > > +static int intel_pmc_get_tco_resources(struct platform_device *pdev,
> > > +				       struct intel_pmc_dev *pmc)
> > > +{
> > > +	struct itco_wdt_platform_data *pdata;
> > > +	struct resource *res, *tco_res;
> > > +
> > > +	if (acpi_has_watchdog())
> > > +		return 0;
> > > +
> > > +	res = platform_get_resource(pdev, IORESOURCE_IO,
> > > +				    PLAT_RESOURCE_ACPI_IO_INDEX);
> > > +	if (!res) {
> > > +		dev_err(&pdev->dev, "Failed to get IO resource\n");
> > > +		return -EINVAL;
> > > +	}
> > > +
> > > +	tco_res = devm_kcalloc(&pdev->dev, 2, sizeof(*tco_res), GFP_KERNEL);
> > > +	if (!tco_res)
> > > +		return -ENOMEM;
> > > +
> > > +	tco_res[0].flags = IORESOURCE_IO;
> > > +	tco_res[0].start = res->start + TCO_BASE_OFFSET;
> > > +	tco_res[0].end = tco_res[0].start + TCO_REGS_SIZE - 1;
> > > +	tco_res[1].flags = IORESOURCE_IO;
> > > +	tco_res[1].start = res->start + SMI_EN_OFFSET;
> > > +	tco_res[1].end = tco_res[1].start + SMI_EN_SIZE - 1;
> > > +
> > > +	pmc->cells[PMC_TCO].resources = tco_res;
> > > +	pmc->cells[PMC_TCO].num_resources = 2;
> > > +
> > > +	pdata = devm_kmemdup(&pdev->dev, &tco_pdata, sizeof(*pdata), GFP_KERNEL);
> > > +	if (!pdata)
> > > +		return -ENOMEM;
> > > +
> > > +	pdata->no_reboot_priv = pmc;
> > 
> > This looks hacky.  What are you doing here?
> 
> So the pmc instance is created per device as you requested. This one
> passes it to the iTCO_wdt .update_no_reboot_bit() callback which we
> implemented in this driver (sane name update_no_reboot_bit()).
> 
> The iTCO_wdt platform data can be found in this header if you want to
> take a look: include/linux/platform_data/itco_wdt.h.

We usually pass these kinds of pointers via device data, rather than
platform data.

> > > +	pmc->cells[PMC_TCO].platform_data = pdata;
> > > +	pmc->cells[PMC_TCO].pdata_size = sizeof(*pdata);
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +static int intel_pmc_get_resources(struct platform_device *pdev,
> > > +				   struct intel_pmc_dev *pmc,
> > > +				   struct intel_scu_ipc_pdata *pdata)
> > > +{
> > > +	struct resource *res, *punit_res;
> > > +	struct resource gcr_res;
> > > +	size_t npunit_res = 0;
> > > +	int ret;
> > > +
> > > +	pdata->irq = platform_get_irq_optional(pdev, 0);
> > > +
> > > +	res = platform_get_resource(pdev, IORESOURCE_MEM,
> > > +				    PLAT_RESOURCE_IPC_INDEX);
> > > +	if (!res) {
> > > +		dev_err(&pdev->dev, "Failed to get IPC resource\n");
> > > +		return -EINVAL;
> > > +	}
> > > +
> > > +	/* IPC registers */
> > > +	pdata->mem.flags = res->flags;
> > > +	pdata->mem.start = res->start;
> > > +	pdata->mem.end = res->start + PLAT_RESOURCE_IPC_SIZE - 1;
> > 
> > Passing register addresses through pdata also looks like a hack.
> > 
> > Why not pass via resources?
> 
> It is not actual "platform data" but just a structure that we pass for
> the IPC registration function that then creates the underlying device
> for the SCU IPC using these. Since it is plain device (not struct
> platform device) it does not have the concept of "resources" such as
> platform devices have.

Calling something platform data that isn't platform data is confusing.

Why aren't you using the standard device driver model to register this
device?

[...]

> > > diff --git a/include/linux/mfd/intel_pmc_bxt.h b/include/linux/mfd/intel_pmc_bxt.h
> > > new file mode 100644
> > > index 000000000000..a5fb41910d78
> > > --- /dev/null
> > > +++ b/include/linux/mfd/intel_pmc_bxt.h
> > > @@ -0,0 +1,21 @@
> > > +/* SPDX-License-Identifier: GPL-2.0 */
> > > +#ifndef MFD_INTEL_PMC_BXT_H
> > > +#define MFD_INTEL_PMC_BXT_H
> > > +
> > > +#include <linux/types.h>
> > > +
> > > +/* GCR reg offsets from GCR base */
> > > +#define PMC_GCR_PMC_CFG_REG		0x08
> > > +#define PMC_GCR_TELEM_DEEP_S0IX_REG	0x78
> > > +#define PMC_GCR_TELEM_SHLW_S0IX_REG	0x80
> > > +
> > > +/*
> > > + * Pointer to the PMC device can be obtained by calling
> > > + * dev_get_drvdata() to the parent MFD device.
> > > + */
> > > +struct intel_pmc_dev;
> > 
> > Don't you have a shared header file you can put the definition in
> > instead?
> 
> Unfortunately no. This one is the shared header.

Please consider moving the definition into here then.

-- 
Lee Jones [æçæ]
Linaro Services Technical Lead
Linaro.org â Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog