[PATCH v4 4/4] PCI: mvebu: Add support for sending Set_Slot_Power_Limit message

Pali Rohár
2022-04-11T19:01:40Z

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.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
---
Changes in v2:
* Fix handling of slot power limit with scale x1.0 (0x00 value)
* Use FIELD_PREP instead of _SHIFT macros
* Changed commit message to Bjorn's suggestion
* Changed comments in the code to match PCIe spec
* Preserve user settings of PCI_EXP_SLTCTL_ASPL_DISABLE bit
---
drivers/pci/controller/pci-mvebu.c | 96 ++++++++++++++++++++++++++++--
1 file changed, 91 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/controller/pci-mvebu.c b/drivers/pci/controller/pci-mvebu.c
index a75d2b9196f9..26ae7c29fece 100644
--- a/drivers/pci/controller/pci-mvebu.c
+++ b/drivers/pci/controller/pci-mvebu.c
@@ -8,6 +8,7 @@
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/pci.h>
+#include <linux/bitfield.h>
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/gpio.h>
@@ -66,6 +67,12 @@
#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 +118,8 @@ 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 +248,7 @@ 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 +301,20 @@ 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 Port to automatically send Set_Slot_Power_Limit
+ * PCIe Message when changing status from Dl_Down to Dl_Up and valid
+ * slot power limit was specified.
+ */
+ 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) {
+ 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 +651,23 @@ 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;
+ /*
+ * When slot power limit was not specified in DT then
+ * ASPL_DISABLE bit is stored only in emulated config space.
+ * Otherwise reflect status of PCIE_SSPL_ENABLE bit in HW.
+ */
+ if (!port->slot_power_limit_value)
+ val |= slotctl & PCI_EXP_SLTCTL_ASPL_DISABLE;
+ else if (!(mvebu_readl(port, PCIE_SSPL_OFF) & PCIE_SSPL_ENABLE))
+ val |= PCI_EXP_SLTCTL_ASPL_DISABLE;
+ /* This callback is 32-bit and in high bits is slot status. */
+ val |= slotsta << 16;
+ *value = val;
break;
+ }

case PCI_EXP_RTSTA:
*value = mvebu_readl(port, PCIE_RC_RTSTA);
@@ -774,6 +811,22 @@ 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:
+ /*
+ * Allow to change PCIE_SSPL_ENABLE bit only when slot power
+ * limit was specified in DT and configured into HW.
+ */
+ if ((mask & PCI_EXP_SLTCTL_ASPL_DISABLE) &&
+ port->slot_power_limit_value) {
+ 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);
+ }
+ break;
+
case PCI_EXP_RTSTA:
/*
* PME Status bit in Root Status Register (PCIE_RC_RTSTA)
@@ -868,8 +921,26 @@ 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(
+ FIELD_PREP(PCI_EXP_SLTCAP_SPLV, port->slot_power_limit_value) |
+ FIELD_PREP(PCI_EXP_SLTCAP_SPLS, port->slot_power_limit_scale) |
+ FIELD_PREP(PCI_EXP_SLTCAP_PSN, port->port+1));
+ 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 +1262,7 @@ 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 +1363,15 @@ 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 +1668,7 @@ 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 +1705,11 @@ 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