PCI: brcmstb: add support for BCM2712 priority forwarding

The BCM2712 root complexes can interpret priority signalling in two
different ways, based on the incoming Traffic Class of a TLP.

The TLP TCs are assigned to separate internal request/response queues,
and assigned different AXI IDs. These queues can have outgoing AXI
transactions tagged based on:

- Static QoS values
- Dynamic QoS through internal backpressure
- Dynamic QoS with elevation based on Vendor Messages received by the RC

The VDM mechanism is of limited use due to implementation bugs, but the
implicit reordering due to separate ID assignment allows higher-priority
traffic from an EP to overtake other traffic in the RC and rest of the
system.

RP1 assigns TCs based on its internal bus managers, and internally tags
read requests to allow out-of-order completions, so these two features
operate in concert to provide priority service to e.g. MIPI camera or
display traffic.

Signed-off-by: Jonathan Bell <jonathan@raspberrypi.com>

Author: P33M

drivers/pci/controller/pcie-brcmstb.c

@@ -213,6 +213,22 @@
 #define  PCIE_DVT_PMU_PCIE_PHY_CTRL_DAST_PWRDN_SHIFT		0x0
 
 /* BCM7712/2712-specific registers */
+
+#define PCIE_RC_TL_VDM_CTL0				0x0a20
+#define  PCIE_RC_TL_VDM_CTL0_VDM_ENABLED_MASK		0x10000
+#define  PCIE_RC_TL_VDM_CTL0_VDM_IGNORETAG_MASK		0x20000
+#define  PCIE_RC_TL_VDM_CTL0_VDM_IGNOREVNDRID_MASK	0x40000
+
+#define PCIE_RC_TL_VDM_CTL1				0x0a0c
+#define  PCIE_RC_TL_VDM_CTL1_VDM_VNDRID0_MASK		0x0000ffff
+#define  PCIE_RC_TL_VDM_CTL1_VDM_VNDRID1_MASK		0xffff0000
+
+#define PCIE_MISC_CTRL_1					0x40A0
+#define  PCIE_MISC_CTRL_1_OUTBOUND_TC_MASK			0xf
+#define  PCIE_MISC_CTRL_1_OUTBOUND_NO_SNOOP_MASK		BIT(3)
+#define  PCIE_MISC_CTRL_1_OUTBOUND_RO_MASK			BIT(4)
+#define  PCIE_MISC_CTRL_1_EN_VDM_QOS_CONTROL_MASK		BIT(5)
+
 #define PCIE_MISC_UBUS_CTRL	0x40a4
 #define  PCIE_MISC_UBUS_CTRL_UBUS_PCIE_REPLY_ERR_DIS_MASK	BIT(13)
 #define  PCIE_MISC_UBUS_CTRL_UBUS_PCIE_REPLY_DECERR_DIS_MASK	BIT(19)
@@ -221,6 +237,31 @@
 
 #define PCIE_MISC_RC_CONFIG_RETRY_TIMEOUT	0x405c
 
+/* AXI priority forwarding - automatic level-based */
+#define PCIE_MISC_TC_QUEUE_TO_QOS_MAP(x)		(0x4160 - (x) * 4)
+/* Defined in quarter-fullness */
+#define  QUEUE_THRESHOLD_34_TO_QOS_MAP_SHIFT		12
+#define  QUEUE_THRESHOLD_23_TO_QOS_MAP_SHIFT		8
+#define  QUEUE_THRESHOLD_12_TO_QOS_MAP_SHIFT		4
+#define  QUEUE_THRESHOLD_01_TO_QOS_MAP_SHIFT		0
+#define  QUEUE_THRESHOLD_MASK				0xf
+
+/* VDM messages indexing TCs to AXI priorities */
+/* Indexes 8-15 */
+#define PCIE_MISC_VDM_PRIORITY_TO_QOS_MAP_HI		0x4164
+/* Indexes 0-7 */
+#define PCIE_MISC_VDM_PRIORITY_TO_QOS_MAP_LO		0x4168
+#define  VDM_PRIORITY_TO_QOS_MAP_SHIFT(x)		(4 * (x))
+#define  VDM_PRIORITY_TO_QOS_MAP_MASK			0xf
+
+#define PCIE_MISC_AXI_INTF_CTRL 0x416C
+#define  AXI_EN_RCLK_QOS_ARRAY_FIX			BIT(13)
+#define  AXI_EN_QOS_UPDATE_TIMING_FIX			BIT(12)
+#define  AXI_DIS_QOS_GATING_IN_MASTER			BIT(11)
+#define  AXI_REQFIFO_EN_QOS_PROPAGATION			BIT(7)
+#define  AXI_BRIDGE_LOW_LATENCY_MODE			BIT(6)
+#define  AXI_MASTER_MAX_OUTSTANDING_REQUESTS_MASK	0x3f
+
 #define PCIE_MISC_AXI_READ_ERROR_DATA		0x4170
 
 /* Forward declarations */
@@ -856,6 +897,7 @@ static int brcm_pcie_post_setup_bcm2712(struct brcm_pcie *pcie)
 	const u8 regs[] = { 0x16, 0x17, 0x18, 0x19, 0x1b, 0x1c, 0x1e };
 	int ret, i;
 	u32 tmp;
+	u8 qos_map[8];
 
 	/* Allow a 54MHz (xosc) refclk source */
 	ret = brcm_pcie_mdio_write(pcie->base, MDIO_PORT0, SET_ADDR_OFFSET, 0x1600);
@@ -903,6 +945,84 @@ static int brcm_pcie_post_setup_bcm2712(struct brcm_pcie *pcie)
 	writel(0xB2D0000, pcie->base + PCIE_MISC_UBUS_TIMEOUT);
 	writel(0xABA0000, pcie->base + PCIE_MISC_RC_CONFIG_RETRY_TIMEOUT);
 
+	/*
+	 * BCM2712 has a configurable QoS mechanism that assigns TLP Traffic Classes
+	 * to separate AXI IDs with a configurable priority scheme.
+	 * Dynamic priority elevation is supported through reception of Type 1
+	 * Vendor Defined Messages, but several bugs make this largely ineffective.
+	 */
+
+	/* Disable broken forwarding search. Set chicken bits for 2712D0 */
+	tmp = readl(pcie->base + PCIE_MISC_AXI_INTF_CTRL);
+	tmp &= ~AXI_REQFIFO_EN_QOS_PROPAGATION;
+	tmp |= AXI_EN_RCLK_QOS_ARRAY_FIX | AXI_EN_QOS_UPDATE_TIMING_FIX |
+		AXI_DIS_QOS_GATING_IN_MASTER;
+	writel(tmp, pcie->base + PCIE_MISC_AXI_INTF_CTRL);
+
+	/*
+	 * Work around spurious QoS=0 assignments to inbound traffic.
+	 * If the QOS_UPDATE_TIMING_FIX bit is Reserved-0, then this is a
+	 * 2712C1 chip, or a single-lane RC. Use the best-effort alternative
+	 * which is to partially throttle AXI requests in-flight to SDRAM.
+	 */
+	tmp = readl(pcie->base + PCIE_MISC_AXI_INTF_CTRL);
+	if (!(tmp & AXI_EN_QOS_UPDATE_TIMING_FIX)) {
+		tmp &= ~AXI_MASTER_MAX_OUTSTANDING_REQUESTS_MASK;
+		tmp |= 15;
+		writel(tmp, pcie->base + PCIE_MISC_AXI_INTF_CTRL);
+	}
+
+	/* Disable VDM reception by default */
+	tmp = readl(pcie->base + PCIE_MISC_CTRL_1);
+	tmp &= ~PCIE_MISC_CTRL_1_EN_VDM_QOS_CONTROL_MASK;
+	writel(tmp, pcie->base + PCIE_MISC_CTRL_1);
+
+	if (!of_property_read_u8_array(pcie->np, "brcm,fifo-qos-map", qos_map, 4)) {
+
+		/*
+		 * Backpressure mode - each element is QoS for each
+		 * quartile of FIFO level. Each TC gets the same map, because
+		 * this mode is intended for nonrealtime EPs.
+		 */
+		tmp = 0;
+		for (i = 0; i < 4; i++) {
+			/* Priorities range from 0-15 */
+			qos_map[i] &= 0x0f;
+			tmp |= qos_map[i] << (i * 4);
+		}
+		for (i = 0; i < 8; i++)
+			writel(tmp, pcie->base + PCIE_MISC_TC_QUEUE_TO_QOS_MAP(i));
+
+	} else if (!of_property_read_u8_array(pcie->np, "brcm,vdm-qos-map", qos_map, 8)) {
+		/* Enable VDM reception */
+		tmp = readl(pcie->base + PCIE_MISC_CTRL_1);
+		tmp |= PCIE_MISC_CTRL_1_EN_VDM_QOS_CONTROL_MASK;
+		writel(tmp, pcie->base + PCIE_MISC_CTRL_1);
+
+		tmp = 0;
+		for (i = 0; i < 8; i++) {
+			/* Priorities range from 0-15 */
+			qos_map[i] &= 0x0f;
+			tmp |= qos_map[i] << (i * 4);
+		}
+		/* Broken forwarding means no point separating panic priorities from normal */
+		writel(tmp, pcie->base + PCIE_MISC_VDM_PRIORITY_TO_QOS_MAP_LO);
+		writel(tmp, pcie->base + PCIE_MISC_VDM_PRIORITY_TO_QOS_MAP_HI);
+
+		/* Match Vendor ID of 0 */
+		writel(0, pcie->base + PCIE_RC_TL_VDM_CTL1);
+
+		/*
+		 * Forward VDMs to priority interface anyway -
+		 * useful for debugging starvation through the received VDM count fields.
+		 */
+		tmp = readl(pcie->base + PCIE_RC_TL_VDM_CTL0);
+		tmp |= PCIE_RC_TL_VDM_CTL0_VDM_ENABLED_MASK |
+			PCIE_RC_TL_VDM_CTL0_VDM_IGNORETAG_MASK |
+			PCIE_RC_TL_VDM_CTL0_VDM_IGNOREVNDRID_MASK;
+		writel(tmp, pcie->base + PCIE_RC_TL_VDM_CTL0);
+	}
+
 	return 0;
 }