qti: Add SPMI PMIC arbitrator driver

This patch adds a very rudimentary driver for the SPMI arbitrator used
to access the PMIC. It doesn't support all the controller's actual
arbitration features, so it should probably not be used concurrently
with a running kernel (and it's also not optimized for performance). But
it can be used to set a few registers during boot or on shutdown to
control reset handling, which is all we need it for.

Change-Id: I8631c34a2a89ac71aa1ec9b8266e818c922fe34a
Signed-off-by: Julius Werner <jwerner@chromium.org>

plat/qti/common/inc/spmi_arb.h

@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2020, Google LLC. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef SPMI_ARB_H
+#define SPMI_ARB_H
+
+#include <stdint.h>
+
+/*******************************************************************************
+ * WARNING: This driver does not arbitrate access with the kernel. These APIs
+ * must only be called when the kernel is known to be quiesced (such as before
+ * boot or while the system is shutting down).
+ ******************************************************************************/
+
+/* 32-bit addresses combine (U)SID, PID and register address. */
+
+int spmi_arb_read8(uint32_t addr);
+int spmi_arb_write8(uint32_t addr, uint8_t data);
+
+#endif /* SPMI_ARB_H */

plat/qti/common/src/spmi_arb.c

@@ -0,0 +1,113 @@
+/*
+ * Copyright (c) 2020, Google LLC. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <common/debug.h>
+#include <drivers/delay_timer.h>
+#include <lib/mmio.h>
+
+#include <spmi_arb.h>
+
+#define REG_APID_MAP(apid)	(0x0C440900 + 4 * i)
+#define NUM_APID		0x80
+
+#define PPID_MASK		(0xfff << 8)
+
+#define REG_ARB_CMD(apid)	(0x0C600000 + 0x10000 * apid)
+/* These are opcodes specific to this SPMI arbitrator, *not* SPMI commands. */
+#define OPC_EXT_WRITEL		0
+#define OPC_EXT_READL		1
+
+#define REG_ARB_STATUS(apid)	(0x0C600008 + 0x10000 * apid)
+#define ARB_STATUS_DONE		BIT(0)
+#define ARB_STATUS_FAILURE	BIT(1)
+#define ARB_STATUS_DENIED	BIT(2)
+#define ARB_STATUS_DROPPED	BIT(3)
+
+/* Fake status to report driver errors. */
+#define ARB_FAKE_STATUS_TIMEOUT	BIT(8)
+
+#define REG_ARB_RDATA0(apid)	(0x0C600018 + 0x10000 * apid)
+#define REG_ARB_WDATA0(apid)	(0x0C600010 + 0x10000 * apid)
+
+static int addr_to_apid(uint32_t addr)
+{
+	unsigned int i;
+
+	for (i = 0U; i < NUM_APID; i++) {
+		uint32_t reg = mmio_read_32(REG_APID_MAP(i));
+		if ((reg != 0U) && ((addr & PPID_MASK) == (reg & PPID_MASK))) {
+			return i;
+		}
+	}
+
+	return -1;
+}
+
+static int wait_for_done(uint16_t apid)
+{
+	unsigned int timeout = 100;
+
+	while (timeout-- != 0U) {
+		uint32_t status = mmio_read_32(REG_ARB_STATUS(apid));
+		if ((status & ARB_STATUS_DONE) != 0U) {
+			if ((status & ARB_STATUS_FAILURE) != 0U ||
+			    (status & ARB_STATUS_DENIED) != 0U ||
+			    (status & ARB_STATUS_DROPPED) != 0U) {
+				return status & 0xff;
+			}
+			return 0;
+		}
+		mdelay(1);
+	}
+	ERROR("SPMI_ARB timeout!\n");
+	return ARB_FAKE_STATUS_TIMEOUT;
+}
+
+static void arb_command(uint16_t apid, uint8_t opcode, uint32_t addr,
+			uint8_t bytes)
+{
+	mmio_write_32(REG_ARB_CMD(apid), (uint32_t)opcode << 27 |
+					 (addr & 0xff) << 4 | (bytes - 1));
+}
+
+int spmi_arb_read8(uint32_t addr)
+{
+	int apid = addr_to_apid(addr);
+
+	if (apid < 0) {
+		return apid;
+	}
+
+	arb_command(apid, OPC_EXT_READL, addr, 1);
+
+	int ret = wait_for_done(apid);
+	if (ret != 0) {
+		ERROR("SPMI_ARB read error [0x%x]: 0x%x\n", addr, ret);
+		return ret;
+	}
+
+	return mmio_read_32(REG_ARB_RDATA0(apid)) & 0xff;
+}
+
+int spmi_arb_write8(uint32_t addr, uint8_t data)
+{
+	int apid = addr_to_apid(addr);
+
+	if (apid < 0) {
+		return apid;
+	}
+
+	mmio_write_32(REG_ARB_WDATA0(apid), data);
+	arb_command(apid, OPC_EXT_WRITEL, addr, 1);
+
+	int ret = wait_for_done(apid);
+	if (ret != 0) {
+		ERROR("SPMI_ARB write error [0x%x] = 0x%x: 0x%x\n",
+		      addr, data, ret);
+	}
+
+	return ret;
+}