Re: [PATCH dt + pci 2/2] PCI: Add function for parsing `slot-power-limit-milliwatt` DT property

["Pali Rohár" <pali@kernel.org>]

On Wednesday 12 January 2022 16:08:15 Bjorn Helgaas wrote:
> On Sun, Oct 31, 2021 at 04:07:06PM +0100, Marek Behún wrote:
> > From: Pali Rohár <pali@kernel.org>
> > 
> > Add function of_pci_get_slot_power_limit(), which parses the
> > `slot-power-limit-milliwatt` DT property, returning the value in
> > milliwatts and in format ready for the PCIe Slot Capabilities Register.
> > 
> > Signed-off-by: Pali Rohár <pali@kernel.org>
> > Signed-off-by: Marek Behún <kabel@kernel.org>
> 
> Acked-by: Bjorn Helgaas <bhelgaas@google.com>
> 
> Do we have a caller of of_pci_get_slot_power_limit() yet?  I didn't
> see one from a quick look
> (https://lore.kernel.org/linux-pci/?q=b%3Aof_pci_get_slot_power_limit).
> 
> Let's merge this when we have a user for it.

I have a patch for both pci-mvebu.c and pci-aardvark.c drivers. But
there are lot of patches for these drivers waiting on mailing list for
review... Should I sent another patch for pci-mvebu.c which will use
this of_pci_get_slot_power_limit() function?

> > ---
> >  drivers/pci/of.c  | 64 +++++++++++++++++++++++++++++++++++++++++++++++
> >  drivers/pci/pci.h | 15 +++++++++++
> >  2 files changed, 79 insertions(+)
> > 
> > diff --git a/drivers/pci/of.c b/drivers/pci/of.c
> > index d84381ce82b5..9c1a38d5dd99 100644
> > --- a/drivers/pci/of.c
> > +++ b/drivers/pci/of.c
> > @@ -627,3 +627,67 @@ int of_pci_get_max_link_speed(struct device_node *node)
> >  	return max_link_speed;
> >  }
> >  EXPORT_SYMBOL_GPL(of_pci_get_max_link_speed);
> > +
> > +/**
> > + * of_pci_get_slot_power_limit - Parses the "slot-power-limit-milliwatt"
> > + *				 property.
> > + *
> > + * @node: device tree node with the slot power limit information
> > + * @slot_power_limit_value: pointer where the value should be stored in PCIe
> > + *			    Slot Capabilities Register format
> > + * @slot_power_limit_scale: pointer where the scale should be stored in PCIe
> > + *			    Slot Capabilities Register format
> > + *
> > + * Returns the slot power limit in milliwatts and if @slot_power_limit_value
> > + * and @slot_power_limit_scale pointers are non-NULL, fills in the value and
> > + * scale in format used by PCIe Slot Capabilities Register.
> > + *
> > + * If the property is not found or is invalid, returns 0.
> > + */
> > +u32 of_pci_get_slot_power_limit(struct device_node *node,
> > +				u8 *slot_power_limit_value,
> > +				u8 *slot_power_limit_scale)
> > +{
> > +	u32 slot_power_limit;
> > +	u8 value, scale;
> > +
> > +	if (of_property_read_u32(node, "slot-power-limit-milliwatt",
> > +				 &slot_power_limit))
> > +		slot_power_limit = 0;
> > +
> > +	/* Calculate Slot Power Limit Value and Slot Power Limit Scale */
> > +	if (slot_power_limit == 0) {
> > +		value = 0x00;
> > +		scale = 0;
> > +	} else if (slot_power_limit <= 255) {
> > +		value = slot_power_limit;
> > +		scale = 3;
> > +	} else if (slot_power_limit <= 255*10) {
> > +		value = slot_power_limit / 10;
> > +		scale = 2;
> > +	} else if (slot_power_limit <= 255*100) {
> > +		value = slot_power_limit / 100;
> > +		scale = 1;
> > +	} else if (slot_power_limit <= 239*1000) {
> > +		value = slot_power_limit / 1000;
> > +		scale = 0;
> > +	} else if (slot_power_limit <= 250*1000) {
> > +		value = 0xF0;
> > +		scale = 0;
> > +	} else if (slot_power_limit <= 275*1000) {
> > +		value = 0xF1;
> > +		scale = 0;
> > +	} else {
> > +		value = 0xF2;
> > +		scale = 0;
> > +	}
> > +
> > +	if (slot_power_limit_value)
> > +		*slot_power_limit_value = value;
> > +
> > +	if (slot_power_limit_scale)
> > +		*slot_power_limit_scale = scale;
> > +
> > +	return slot_power_limit;
> > +}
> > +EXPORT_SYMBOL_GPL(of_pci_get_slot_power_limit);
> > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> > index 1cce56c2aea0..9352278141be 100644
> > --- a/drivers/pci/pci.h
> > +++ b/drivers/pci/pci.h
> > @@ -665,6 +665,9 @@ struct device_node;
> >  int of_pci_parse_bus_range(struct device_node *node, struct resource *res);
> >  int of_get_pci_domain_nr(struct device_node *node);
> >  int of_pci_get_max_link_speed(struct device_node *node);
> > +u32 of_pci_get_slot_power_limit(struct device_node *node,
> > +				u8 *slot_power_limit_value,
> > +				u8 *slot_power_limit_scale);
> >  void pci_set_of_node(struct pci_dev *dev);
> >  void pci_release_of_node(struct pci_dev *dev);
> >  void pci_set_bus_of_node(struct pci_bus *bus);
> > @@ -691,6 +694,18 @@ of_pci_get_max_link_speed(struct device_node *node)
> >  	return -EINVAL;
> >  }
> >  
> > +static inline u32
> > +of_pci_get_slot_power_limit(struct device_node *node,
> > +			    u8 *slot_power_limit_value,
> > +			    u8 *slot_power_limit_scale)
> > +{
> > +	if (slot_power_limit_value)
> > +		*slot_power_limit_value = 0;
> > +	if (slot_power_limit_scale)
> > +		*slot_power_limit_scale = 0;
> > +	return 0;
> > +}
> > +
> >  static inline void pci_set_of_node(struct pci_dev *dev) { }
> >  static inline void pci_release_of_node(struct pci_dev *dev) { }
> >  static inline void pci_set_bus_of_node(struct pci_bus *bus) { }
> > -- 
> > 2.32.0
> >