On Tue, Feb 22, 2022 at 05:31:57PM +0100, Pali Rohár wrote: > This PCIe message is sent automatically by mvebu HW when link changes > status from down to up. I *think* the intent of the above is: If DT supplies the 'slot-power-limit-milliwatt' property, program the value in the Slot Power Limit in the Slot Capabilities register and program the Root Port to send a Set_Slot_Power_Limit Message when the Link transitions to DL_Up. PCIe r6.0, sec 2.2.8.5 and 7.5.3.9, also say Set_Slot_Power_Limit must be sent on a config write to Slot Capabilities. I don't really understand that, since AFAICS, everything in that register is read-only. But there must be some use case for forcing a message. > Slot power limit is read from DT property 'slot-power-limit-milliwatt' and > set to mvebu HW. When this DT property is not specified then driver treat > it as "Slot Capabilities register has not yet been initialized". Does this last sentence mean "the Slot Power Limit is set to 0W (Value = 00h and Scale = 00b = 1.0x) and Auto Slot Power Limit Disable is set, so Set_Slot_Power_Limit Messages will never be sent"? > Signed-off-by: Pali Rohár <pali@xxxxxxxxxx> > --- > drivers/pci/controller/pci-mvebu.c | 85 ++++++++++++++++++++++++++++-- > 1 file changed, 80 insertions(+), 5 deletions(-) > > diff --git a/drivers/pci/controller/pci-mvebu.c b/drivers/pci/controller/pci-mvebu.c > index a75d2b9196f9..c786feec4d17 100644 > --- a/drivers/pci/controller/pci-mvebu.c > +++ b/drivers/pci/controller/pci-mvebu.c > @@ -66,6 +66,12 @@ > #define PCIE_STAT_BUS 0xff00 > #define PCIE_STAT_DEV 0x1f0000 > #define PCIE_STAT_LINK_DOWN BIT(0) > +#define PCIE_SSPL_OFF 0x1a0c > +#define PCIE_SSPL_VALUE_SHIFT 0 > +#define PCIE_SSPL_VALUE_MASK GENMASK(7, 0) > +#define PCIE_SSPL_SCALE_SHIFT 8 > +#define PCIE_SSPL_SCALE_MASK GENMASK(9, 8) > +#define PCIE_SSPL_ENABLE BIT(16) > #define PCIE_RC_RTSTA 0x1a14 > #define PCIE_DEBUG_CTRL 0x1a60 > #define PCIE_DEBUG_SOFT_RESET BIT(20) > @@ -111,6 +117,8 @@ struct mvebu_pcie_port { > struct mvebu_pcie_window iowin; > u32 saved_pcie_stat; > struct resource regs; > + u8 slot_power_limit_value; > + u8 slot_power_limit_scale; > struct irq_domain *intx_irq_domain; > raw_spinlock_t irq_lock; > int intx_irq; > @@ -239,7 +247,7 @@ static void mvebu_pcie_setup_wins(struct mvebu_pcie_port *port) > > static void mvebu_pcie_setup_hw(struct mvebu_pcie_port *port) > { > - u32 ctrl, lnkcap, cmd, dev_rev, unmask; > + u32 ctrl, lnkcap, cmd, dev_rev, unmask, sspl; > > /* Setup PCIe controller to Root Complex mode. */ > ctrl = mvebu_readl(port, PCIE_CTRL_OFF); > @@ -292,6 +300,20 @@ static void mvebu_pcie_setup_hw(struct mvebu_pcie_port *port) > /* Point PCIe unit MBUS decode windows to DRAM space. */ > mvebu_pcie_setup_wins(port); > > + /* > + * Program Root Complex to automatically sends Set Slot Power Limit > + * PCIe Message when changing status from Dl-Down to Dl-Up and valid > + * slot power limit was specified. s/Root Complex/Root Port/, right? AFAIK the message would be sent by a Downstream Port, i.e., a Root Port in this case. s/sends/send/ s/Set Slot Power Limit/Set_Slot_Power_Limit/ to match spec usage (also below) s/Dl-Down/DL_Down/ to match spec usage s/Dl-Up/DL_Up/ ditto > + */ > + sspl = mvebu_readl(port, PCIE_SSPL_OFF); > + sspl &= ~(PCIE_SSPL_VALUE_MASK | PCIE_SSPL_SCALE_MASK | PCIE_SSPL_ENABLE); > + if (port->slot_power_limit_value && port->slot_power_limit_scale) { > + sspl |= port->slot_power_limit_value << PCIE_SSPL_VALUE_SHIFT; > + sspl |= port->slot_power_limit_scale << PCIE_SSPL_SCALE_SHIFT; > + sspl |= PCIE_SSPL_ENABLE; > + } > + mvebu_writel(port, sspl, PCIE_SSPL_OFF); > + > /* Mask all interrupt sources. */ > mvebu_writel(port, ~PCIE_INT_ALL_MASK, PCIE_INT_UNMASK_OFF); > > @@ -628,9 +650,16 @@ mvebu_pci_bridge_emul_pcie_conf_read(struct pci_bridge_emul *bridge, > (PCI_EXP_LNKSTA_DLLLA << 16) : 0); > break; > > - case PCI_EXP_SLTCTL: > - *value = PCI_EXP_SLTSTA_PDS << 16; > + case PCI_EXP_SLTCTL: { > + u16 slotsta = le16_to_cpu(bridge->pcie_conf.slotsta); > + u32 val = 0; > + if (!(mvebu_readl(port, PCIE_SSPL_OFF) & PCIE_SSPL_ENABLE)) > + val |= PCI_EXP_SLTCTL_ASPL_DISABLE; > + /* PCI_EXP_SLTCTL is 32-bit and contains also slot status bits */ This comment is a little bit confusing because PCI_EXP_SLTCTL is not actually 32 bits; it's 16 bits. It's just that we "read" 32 bits, which includes both PCI_EXP_SLTCTL and PCI_EXP_SLTSTA. If you use "PCI_EXP_SLTCTL", I think it would be helpful to also say "PCI_EXP_SLTSTA" instead of "slot status bits". > + val |= slotsta << 16; > + *value = val; > break; > + } > > case PCI_EXP_RTSTA: > *value = mvebu_readl(port, PCIE_RC_RTSTA); > @@ -774,6 +803,19 @@ mvebu_pci_bridge_emul_pcie_conf_write(struct pci_bridge_emul *bridge, > mvebu_writel(port, new, PCIE_CAP_PCIEXP + PCI_EXP_LNKCTL); > break; > > + case PCI_EXP_SLTCTL: > + if ((mask & PCI_EXP_SLTCTL_ASPL_DISABLE) && > + port->slot_power_limit_value && > + port->slot_power_limit_scale) { > + u32 sspl = mvebu_readl(port, PCIE_SSPL_OFF); > + if (new & PCI_EXP_SLTCTL_ASPL_DISABLE) > + sspl &= ~PCIE_SSPL_ENABLE; > + else > + sspl |= PCIE_SSPL_ENABLE; > + mvebu_writel(port, sspl, PCIE_SSPL_OFF); IIUC, the behavior of PCI_EXP_SLTCTL_ASPL_DISABLE as observed by software that sets it and reads it back will depend on whether the DT contains "slot-power-limit-milliwatt". If there is no DT property, port->slot_power_limit_value will be zero and PCIE_SSPL_ENABLE will never be set. So if I clear PCI_EXP_SLTCTL_ASPL_DISABLE, then read it back, it looks like it will read as being set. That's not what I would expect from the spec (PCIe r6.0, sec 7.5.3.10). > + } > + break; > + > case PCI_EXP_RTSTA: > /* > * PME Status bit in Root Status Register (PCIE_RC_RTSTA) > @@ -868,8 +910,26 @@ static int mvebu_pci_bridge_emul_init(struct mvebu_pcie_port *port) > /* > * Older mvebu hardware provides PCIe Capability structure only in > * version 1. New hardware provides it in version 2. > + * Enable slot support which is emulated. > */ > - bridge->pcie_conf.cap = cpu_to_le16(pcie_cap_ver); > + bridge->pcie_conf.cap = cpu_to_le16(pcie_cap_ver | PCI_EXP_FLAGS_SLOT); > + > + /* > + * Set Presence Detect State bit permanently as there is no support for > + * unplugging PCIe card from the slot. Assume that PCIe card is always > + * connected in slot. > + * > + * Set physical slot number to port+1 as mvebu ports are indexed from > + * zero and zero value is reserved for ports within the same silicon > + * as Root Port which is not mvebu case. > + * > + * Also set correct slot power limit. > + */ > + bridge->pcie_conf.slotcap = cpu_to_le32( > + (port->slot_power_limit_value << PCI_EXP_SLTCAP_SPLV_SHIFT) | > + (port->slot_power_limit_scale << PCI_EXP_SLTCAP_SPLS_SHIFT) | > + ((port->port+1) << PCI_EXP_SLTCAP_PSN_SHIFT)); > + bridge->pcie_conf.slotsta = cpu_to_le16(PCI_EXP_SLTSTA_PDS); > > bridge->subsystem_vendor_id = ssdev_id & 0xffff; > bridge->subsystem_id = ssdev_id >> 16; > @@ -1191,6 +1251,7 @@ static int mvebu_pcie_parse_port(struct mvebu_pcie *pcie, > { > struct device *dev = &pcie->pdev->dev; > enum of_gpio_flags flags; > + u32 slot_power_limit; > int reset_gpio, ret; > u32 num_lanes; > > @@ -1291,6 +1352,15 @@ static int mvebu_pcie_parse_port(struct mvebu_pcie *pcie, > port->reset_gpio = gpio_to_desc(reset_gpio); > } > > + slot_power_limit = of_pci_get_slot_power_limit(child, > + &port->slot_power_limit_value, > + &port->slot_power_limit_scale); > + if (slot_power_limit) > + dev_info(dev, "%s: Slot power limit %u.%uW\n", > + port->name, > + slot_power_limit / 1000, > + (slot_power_limit / 100) % 10); > + > port->clk = of_clk_get_by_name(child, NULL); > if (IS_ERR(port->clk)) { > dev_err(dev, "%s: cannot get clock\n", port->name); > @@ -1587,7 +1657,7 @@ static int mvebu_pcie_remove(struct platform_device *pdev) > { > struct mvebu_pcie *pcie = platform_get_drvdata(pdev); > struct pci_host_bridge *bridge = pci_host_bridge_from_priv(pcie); > - u32 cmd; > + u32 cmd, sspl; > int i; > > /* Remove PCI bus with all devices. */ > @@ -1624,6 +1694,11 @@ static int mvebu_pcie_remove(struct platform_device *pdev) > /* Free config space for emulated root bridge. */ > pci_bridge_emul_cleanup(&port->bridge); > > + /* Disable sending Set Slot Power Limit PCIe Message. */ > + sspl = mvebu_readl(port, PCIE_SSPL_OFF); > + sspl &= ~(PCIE_SSPL_VALUE_MASK | PCIE_SSPL_SCALE_MASK | PCIE_SSPL_ENABLE); > + mvebu_writel(port, sspl, PCIE_SSPL_OFF); > + > /* Disable and clear BARs and windows. */ > mvebu_pcie_disable_wins(port); > > -- > 2.20.1 >