Re: [PATCH] ACPI: platform: Add basic support for ACPI 6.5 fixed clock resources

[Paul Cercueil <paul.cercueil@bootlin.com>]

Hi Rafael,

Le mardi 10 novembre 2026 à 18:18 +0100, Rafael J. Wysocki (Intel) a écrit :
> On Tue, Nov 3, 2026 at 9:47 AM Paul Cercueil <paul.cercueil@bootlin.com>
> wrote:
> > 
> > ACPI 6.5 introduced a clock input resource descriptor, which allows to
> > specify in the ACPI tables what clocks are connected to a given device.
> > 
> > This patch adds support for the most basic clock resource, which is the
> > one that represents a fixed clock. The new code will then create a
> > clk_hw for each fixed clock resource, which is then made available to
> > the device drivers, that can obtain it through a regular call to
> > clk_get(NULL).
> > 
> > Signed-off-by: Paul Cercueil <paul.cercueil@bootlin.com>
> 
> You need to look at Sashiko's feedback on this:
> 
> https://sashiko.dev/#/patchset/20261103084718.8222-1-paul.cercueil%40bootlin.com

I was expecting Sashiko to send me an email, but it didn't?

I'll v2 with the feedback addressed.

Cheers,
-Paul

> > ---
> >  drivers/acpi/acpi_platform.c | 64 ++++++++++++++++++++++++++++++++++++
> >  1 file changed, 64 insertions(+)
> > 
> > diff --git a/drivers/acpi/acpi_platform.c b/drivers/acpi/acpi_platform.c
> > index 80ea7121744d..bae6a2eacd71 100644
> > --- a/drivers/acpi/acpi_platform.c
> > +++ b/drivers/acpi/acpi_platform.c
> > @@ -10,17 +10,27 @@
> > 
> >  #include <linux/acpi.h>
> >  #include <linux/bits.h>
> > +#include <linux/clk-provider.h>
> > +#include <linux/clkdev.h>
> >  #include <linux/device.h>
> >  #include <linux/err.h>
> >  #include <linux/ioport.h>
> > +#include <linux/kconfig.h>
> >  #include <linux/kernel.h>
> > +#include <linux/list.h>
> >  #include <linux/module.h>
> >  #include <linux/dma-mapping.h>
> >  #include <linux/pci.h>
> >  #include <linux/platform_device.h>
> > +#include <linux/units.h>
> > 
> >  #include "internal.h"
> > 
> > +struct acpi_clk_data {
> > +       struct device *dev;
> > +       unsigned int idx;
> > +};
> > +
> >  /* Exclude devices that have no _CRS resources provided */
> >  #define ACPI_ALLOW_WO_RESOURCES                BIT(0)
> > 
> > @@ -130,6 +140,57 @@ static unsigned int acpi_platform_resource_count(struct
> > acpi_resource *ares, voi
> >         return AE_CTRL_TERMINATE;
> >  }
> > 
> > +static int acpi_add_fixed_clock(struct acpi_resource *res, void *d)
> > +{
> > +       static const unsigned long clk_scale[] = { 1, HZ_PER_KHZ, HZ_PER_MHZ
> > };
> > +       struct acpi_resource_clock_input *clkres;
> > +       struct acpi_clk_data *data = d;
> > +       struct device *dev = data->dev;
> > +       struct clk_hw *clk;
> > +       unsigned long rate;
> > +       char name[64];
> > +       int err;
> > +
> > +       if (res->type == ACPI_RESOURCE_TYPE_CLOCK_INPUT) {
> > +               clkres = &res->data.clock_input;
> > +
> > +               if (clkres->mode) {
> > +                       dev_warn(dev, "Only fixed rate clocks supported for
> > now.\n");
> > +                       return 1; /* keep going */
> > +               }
> > +
> > +               if (clkres->frequency_divisor == 0)
> > +                       return -EINVAL;
> > +
> > +               rate = DIV_ROUND_UP(clkres->frequency_numerator *
> > clk_scale[clkres->scale],
> > +                                   clkres->frequency_divisor);
> > +
> > +               clk = devm_clk_hw_register_fixed_rate(dev, dev_name(dev),
> > NULL, 0, rate);
> > +               if (IS_ERR(clk))
> > +                       return PTR_ERR(clk);
> > +
> > +               snprintf(name, sizeof(name), "%s-clk%u", dev_name(dev),
> > data->idx++);
> > +
> > +               err = devm_clk_hw_register_clkdev(dev, clk, name,
> > dev_name(dev));
> > +               if (err)
> > +                       return err;
> > +       }
> > +
> > +       return 1;
> > +}
> > +
> > +static void acpi_platform_init_clocks(struct acpi_device *adev)
> > +{
> > +       struct device *dev = &adev->dev;
> > +       struct acpi_clk_data data = { .dev = dev };
> > +       LIST_HEAD(list);
> > +       int ret;
> > +
> > +       ret = acpi_dev_get_resources(adev, &list, acpi_add_fixed_clock,
> > &data);
> > +       if (ret < 0)
> > +               dev_err(dev, "Failed to add clock resources: %d\n", ret);
> > +}
> > +
> >  /**
> >   * acpi_create_platform_device - Create platform device for ACPI device
> > node
> >   * @adev: ACPI device node to create a platform device for.
> > @@ -217,6 +278,9 @@ struct platform_device
> > *acpi_create_platform_device(struct acpi_device *adev,
> >         else
> >                 pdevinfo.dma_mask = 0;
> > 
> > +       if (IS_ENABLED(CONFIG_COMMON_CLK))
> > +               acpi_platform_init_clocks(adev);
> > +
> >         pdev = platform_device_register_full(&pdevinfo);
> >         if (IS_ERR(pdev))
> >                 dev_err(&adev->dev, "platform device creation failed:
> > %ld\n",
> > --