| Message ID | 20220302145733.12606-4-pali@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | PCI: mvebu: Slot support | expand |
On Wed, Mar 02, 2022 at 03:57:32PM +0100, Pali Rohár wrote: > 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> > Reviewed-by: Rob Herring <robh@kernel.org> > --- > Changes in v2: > * Added support for PCIe 6.0 slot power limit encodings > * Round down slot power limit value > --- > 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 cb2e8351c2cc..549a404bd536 100644 > --- a/drivers/pci/of.c > +++ b/drivers/pci/of.c > @@ -633,3 +633,67 @@ 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_mw; > + u8 value, scale; > + > + if (of_property_read_u32(node, "slot-power-limit-milliwatt", > + &slot_power_limit_mw)) > + slot_power_limit_mw = 0; > + > + /* Calculate Slot Power Limit Value and Slot Power Limit Scale */ > + if (slot_power_limit_mw == 0) { > + value = 0x00; > + scale = 0; > + } else if (slot_power_limit_mw <= 255) { > + value = slot_power_limit_mw; > + scale = 3; > + } else if (slot_power_limit_mw <= 255*10) { > + value = slot_power_limit_mw / 10; > + scale = 2; > + } else if (slot_power_limit_mw <= 255*100) { > + value = slot_power_limit_mw / 100; > + scale = 1; > + } else if (slot_power_limit_mw <= 239*1000) { > + value = slot_power_limit_mw / 1000; > + scale = 0; > + } else if (slot_power_limit_mw <= 250*1000) { > + value = 0xF0; > + scale = 0; > + } else if (slot_power_limit_mw <= 600*1000) { > + value = 0xF0 + (slot_power_limit_mw / 1000 - 250) / 25; > + scale = 0; > + } else { > + value = 0xFF; > + scale = 0; The purpose of this function is to return values that can be programmed into the Slot Capabilities register. The 0xFF Slot Power Limit Value is reserved, and I don't think we should use it until the spec defines a meaning for it. If the DT tells us 800W is available, we'll put 0xFF in Slot Power Limit Value. If the spec eventually defines (0xFF, 0) to mean "1000W available", a device may try to consume all 1000W, which will not work. If slot_power_limit_mw > 600*1000, I think we should advertise 600W available (value 0xFE, scale 0) and return 600W (600*1000). Bjorn
On Thursday 24 March 2022 12:13:37 Bjorn Helgaas wrote: > On Wed, Mar 02, 2022 at 03:57:32PM +0100, Pali Rohár wrote: > > 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> > > Reviewed-by: Rob Herring <robh@kernel.org> > > --- > > Changes in v2: > > * Added support for PCIe 6.0 slot power limit encodings > > * Round down slot power limit value > > --- > > 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 cb2e8351c2cc..549a404bd536 100644 > > --- a/drivers/pci/of.c > > +++ b/drivers/pci/of.c > > @@ -633,3 +633,67 @@ 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_mw; > > + u8 value, scale; > > + > > + if (of_property_read_u32(node, "slot-power-limit-milliwatt", > > + &slot_power_limit_mw)) > > + slot_power_limit_mw = 0; > > + > > + /* Calculate Slot Power Limit Value and Slot Power Limit Scale */ > > + if (slot_power_limit_mw == 0) { > > + value = 0x00; > > + scale = 0; > > + } else if (slot_power_limit_mw <= 255) { > > + value = slot_power_limit_mw; > > + scale = 3; > > + } else if (slot_power_limit_mw <= 255*10) { > > + value = slot_power_limit_mw / 10; > > + scale = 2; > > + } else if (slot_power_limit_mw <= 255*100) { > > + value = slot_power_limit_mw / 100; > > + scale = 1; > > + } else if (slot_power_limit_mw <= 239*1000) { > > + value = slot_power_limit_mw / 1000; > > + scale = 0; > > + } else if (slot_power_limit_mw <= 250*1000) { > > + value = 0xF0; > > + scale = 0; > > + } else if (slot_power_limit_mw <= 600*1000) { > > + value = 0xF0 + (slot_power_limit_mw / 1000 - 250) / 25; > > + scale = 0; > > + } else { > > + value = 0xFF; > > + scale = 0; > > The purpose of this function is to return values that can be > programmed into the Slot Capabilities register. The 0xFF Slot Power > Limit Value is reserved, and I don't think we should use it until the > spec defines a meaning for it. > > If the DT tells us 800W is available, we'll put 0xFF in Slot Power > Limit Value. If the spec eventually defines (0xFF, 0) to mean "1000W > available", a device may try to consume all 1000W, which will not > work. > > If slot_power_limit_mw > 600*1000, I think we should advertise 600W > available (value 0xFE, scale 0) and return 600W (600*1000). > > Bjorn Ok, I will send a v3 with this change.
diff --git a/drivers/pci/of.c b/drivers/pci/of.c index cb2e8351c2cc..549a404bd536 100644 --- a/drivers/pci/of.c +++ b/drivers/pci/of.c @@ -633,3 +633,67 @@ 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_mw; + u8 value, scale; + + if (of_property_read_u32(node, "slot-power-limit-milliwatt", + &slot_power_limit_mw)) + slot_power_limit_mw = 0; + + /* Calculate Slot Power Limit Value and Slot Power Limit Scale */ + if (slot_power_limit_mw == 0) { + value = 0x00; + scale = 0; + } else if (slot_power_limit_mw <= 255) { + value = slot_power_limit_mw; + scale = 3; + } else if (slot_power_limit_mw <= 255*10) { + value = slot_power_limit_mw / 10; + scale = 2; + } else if (slot_power_limit_mw <= 255*100) { + value = slot_power_limit_mw / 100; + scale = 1; + } else if (slot_power_limit_mw <= 239*1000) { + value = slot_power_limit_mw / 1000; + scale = 0; + } else if (slot_power_limit_mw <= 250*1000) { + value = 0xF0; + scale = 0; + } else if (slot_power_limit_mw <= 600*1000) { + value = 0xF0 + (slot_power_limit_mw / 1000 - 250) / 25; + scale = 0; + } else { + value = 0xFF; + 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_mw; +} +EXPORT_SYMBOL_GPL(of_pci_get_slot_power_limit); diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h index 3d60cabde1a1..e10cdec6c56e 100644 --- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -627,6 +627,9 @@ 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); @@ -653,6 +656,18 @@ 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) { }