intel/common/pmc: Add functions for IPC mailbox in ACPI

This change adds two functions that provide an IPC mailbox method via
ACPI for runtime clock configuration.

pmc_acpi_fill_ssdt_ipc_write_method() will provide a method in the SSDT
that can be called by other ACPI devices to send an IPC mailbox command.
This function is exported because some SOCs override the default PMC
device and need to call this function to write the method into the SSDT.

pmc_acpi_set_pci_clock() will call the method defined by the previous
function to enable or disable the PCIe SRCCLK for a specified root port
and clock pin.  It can be called by the PCIe root port after turning off
power to the attached device.

BUG=b:160996445
TEST=boot on volteer device and disassemble the SSDT to ensure that this
method exists.

Signed-off-by: Duncan Laurie <dlaurie@google.com>
Change-Id: I95f5a1ba2bc6905e0f8ce0e8b2342ad1287a23a0
Reviewed-on: https://review.coreboot.org/c/coreboot/+/46259
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/intel/common/block/include/intelblocks/pmc_ipc.h

@@ -21,6 +21,14 @@
 
 #define PMC_IPC_CMD_NO_MSI		0
 
+/* IPC command to enable/disable PCIe SRCCLK */
+#define PMC_IPC_CMD_ID_SET_PCIE_CLOCK	0xAC
+
+/* IPC return values */
+#define PMC_IPC_SUCCESS			0
+#define PMC_IPC_ERROR			1
+#define PMC_IPC_TIMEOUT			2
+
 /*
  * Create the IPC CMD to send to PMC
  */
@@ -46,4 +54,29 @@ struct pmc_ipc_buffer {
 enum cb_err pmc_send_ipc_cmd(uint32_t cmd, const struct pmc_ipc_buffer *wbuf,
 			     struct pmc_ipc_buffer *rbuf);
 
+/*
+ * Provides an ACPI method in the SSDT to read/write to the IPC mailbox which is
+ * defined in the PMC device MMIO address space.
+ *
+ * One possible use of this method is to to enable/disable the clock for a
+ * particular PCIe root port at runtime when the device is in D3 state.
+ *
+ * The ACPI method takes 7 arguments:
+ *  IPCW (COMMAND, SUB_ID, SIZE, DATA0, DATA1, DATA2, DATA3)
+ *
+ * And will return a package with 5 elements:
+ *  0    = Return code
+ *         PMC_IPC_SUCCESS
+ *         PMC_IPC_ERROR
+ *         PMC_IPC_TIMEOUT
+ *  1..4 = Data read from IPC if return code is PMC_IPC_SUCCESS
+ */
+void pmc_ipc_acpi_fill_ssdt(void);
+
+/*
+ * Call the ACPI method to write to the IPC mailbox and enable/disable the
+ * specified clock pin connected to the specified PCIe root port.
+ */
+void pmc_ipc_acpi_set_pci_clock(unsigned int pcie_rp, unsigned int clock_pin, bool enable);
+
 #endif /* SOC_INTEL_COMMON_BLOCK_PMC_IPC_H */

src/soc/intel/common/block/pmc/Kconfig

@@ -22,6 +22,14 @@ config PMC_INVALID_READ_AFTER_WRITE
 	  Enable this for PMC devices where a read back of ACPI BAR and
 	  IO access bit does not return the previously written value.
 
+config PMC_IPC_ACPI_INTERFACE
+	bool
+	default n
+	depends on HAVE_ACPI_TABLES
+	help
+	  Enable this to have the PMC IPC mailbox ACPI interface added
+	  to the SSDT for use by other drivers.
+
 config PMC_GLOBAL_RESET_ENABLE_LOCK
 	bool
 	help

src/soc/intel/common/block/pmc/Makefile.inc

@@ -6,4 +6,5 @@ ramstage-y += pmclib.c pmc_ipc.c
 smm-y += pmclib.c
 verstage-y += pmclib.c
 postcar-y += pmclib.c
+ramstage-$(CONFIG_PMC_IPC_ACPI_INTERFACE) += pmc_ipc.c
 endif

src/soc/intel/common/block/pmc/pmc_ipc.c

@@ -1,10 +1,12 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
+#include <acpi/acpigen.h>
 #include <device/mmio.h>
 #include <console/console.h>
 #include <delay.h>
 #include <intelblocks/pmclib.h>
 #include <intelblocks/pmc_ipc.h>
+#include <soc/pci_devs.h>
 #include <stdint.h>
 #include <timer.h>
 
@@ -64,16 +66,16 @@ static int check_ipc_sts(void)
 			if (IPC_STS_HAS_ERROR(ipc_sts)) {
 				printk(BIOS_ERR, "IPC_STS.error_code 0x%x\n",
 				       IPC_STS_ERROR_CODE(ipc_sts));
-				return -1;
+				return PMC_IPC_ERROR;
 			}
-			return 0;
+			return PMC_IPC_SUCCESS;
 		}
 		udelay(50);
 
 	} while (!stopwatch_expired(&sw));
 
 	printk(BIOS_ERR, "PMC IPC timeout after %u ms\n", PMC_IPC_XFER_TIMEOUT_MS);
-	return -1;
+	return PMC_IPC_TIMEOUT;
 }
 
 enum cb_err pmc_send_ipc_cmd(uint32_t cmd, const struct pmc_ipc_buffer *wbuf,
@@ -94,3 +96,151 @@ enum cb_err pmc_send_ipc_cmd(uint32_t cmd, const struct pmc_ipc_buffer *wbuf,
 
 	return CB_SUCCESS;
 }
+
+void pmc_ipc_acpi_fill_ssdt(void)
+{
+	const struct fieldlist ipcs_fields[] = {
+		FIELDLIST_OFFSET(PMC_IPC_CMD_OFFSET),	/* Command */
+		FIELDLIST_NAMESTR("ICMD", 32),		/* Command Register */
+		FIELDLIST_OFFSET(PMC_IPC_STS_OFFSET),	/* Status */
+		FIELDLIST_NAMESTR("IBSY", 1),		/* Status Busy */
+		FIELDLIST_NAMESTR("IERR", 1),		/* Status Error */
+		FIELDLIST_RESERVED(14),
+		FIELDLIST_NAMESTR("IERC", 8),		/* Status Error Code */
+		FIELDLIST_OFFSET(IPC_WBUF0),		/* Write Buffer */
+		FIELDLIST_NAMESTR("IWB0", 32),		/* Write Buffer 0 */
+		FIELDLIST_NAMESTR("IWB1", 32),		/* Write Buffer 1 */
+		FIELDLIST_NAMESTR("IWB2", 32),		/* Write Buffer 2 */
+		FIELDLIST_NAMESTR("IWB3", 32),		/* Write Buffer 3 */
+		FIELDLIST_OFFSET(IPC_RBUF0),		/* Read Buffer */
+		FIELDLIST_NAMESTR("IRB0", 32),		/* Read Buffer 0 */
+		FIELDLIST_NAMESTR("IRB1", 32),		/* Read Buffer 1 */
+		FIELDLIST_NAMESTR("IRB2", 32),		/* Read Buffer 2 */
+		FIELDLIST_NAMESTR("IRB3", 32),		/* Read Buffer 3 */
+	};
+	const struct opregion ipcs_opregion = OPREGION("IPCM", SYSTEMMEMORY,
+						       soc_read_pmc_base(), 0xff);
+	int i;
+
+	/* Package with return value and read buffer. */
+	acpigen_write_name("RVAL");
+	acpigen_write_package(5);
+	for (i = 0; i < 5; ++i)
+		acpigen_write_integer(0);
+	acpigen_pop_len();
+
+	acpigen_write_method_serialized("IPCS", 7);
+
+	acpigen_write_opregion(&ipcs_opregion);
+	acpigen_write_field("IPCM", ipcs_fields, ARRAY_SIZE(ipcs_fields),
+			    FIELD_DWORDACC | FIELD_NOLOCK | FIELD_PRESERVE);
+
+	/* Fill write buffer data registers. */
+	acpigen_write_store_op_to_namestr(ARG3_OP, "IWB0");
+	acpigen_write_store_op_to_namestr(ARG4_OP, "IWB1");
+	acpigen_write_store_op_to_namestr(ARG5_OP, "IWB2");
+	acpigen_write_store_op_to_namestr(ARG6_OP, "IWB3");
+
+	/* Program the command register with command and size of write data. */
+	acpigen_write_store_int_to_op(0, LOCAL0_OP);
+
+	/* Local0 += (Arg0 << PMC_IPC_CMD_COMMAND_SHIFT) */
+	acpigen_emit_byte(ADD_OP);
+	acpigen_emit_byte(LOCAL0_OP);
+	acpigen_write_shiftleft_op_int(ARG0_OP, PMC_IPC_CMD_COMMAND_SHIFT);
+	acpigen_emit_byte(LOCAL0_OP);
+
+	/* Local0 += (Arg1 << PMC_IPC_CMD_SUB_COMMAND_SHIFT) */
+	acpigen_emit_byte(ADD_OP);
+	acpigen_emit_byte(LOCAL0_OP);
+	acpigen_write_shiftleft_op_int(ARG1_OP, PMC_IPC_CMD_SUB_COMMAND_SHIFT);
+	acpigen_emit_byte(LOCAL0_OP);
+
+	/* Local1 = PMC_IPC_CMD_NO_MSI */
+	acpigen_write_store_int_to_op(PMC_IPC_CMD_NO_MSI, LOCAL1_OP);
+	/* Local0 += (Local1 << PMC_IPC_CMD_MSI_SHIFT) */
+	acpigen_emit_byte(ADD_OP);
+	acpigen_emit_byte(LOCAL0_OP);
+	acpigen_write_shiftleft_op_int(LOCAL1_OP, PMC_IPC_CMD_MSI_SHIFT);
+	acpigen_emit_byte(LOCAL0_OP);
+
+	/* Local0 += (Arg1 << PMC_IPC_CMD_SIZE_SHIFT) */
+	acpigen_emit_byte(ADD_OP);
+	acpigen_emit_byte(LOCAL0_OP);
+	acpigen_write_shiftleft_op_int(ARG2_OP, PMC_IPC_CMD_SIZE_SHIFT);
+	acpigen_emit_byte(LOCAL0_OP);
+
+	/* Start mailbox command with one 32bit write. */
+	acpigen_write_store_op_to_namestr(LOCAL0_OP, "ICMD");
+
+	/* Read status register to get busy/error status. */
+	acpigen_write_store_int_to_op(PMC_IPC_XFER_TIMEOUT_MS, LOCAL1_OP);
+
+	/* While (Local1 > 0) */
+	acpigen_emit_byte(WHILE_OP);
+	acpigen_write_len_f();
+	acpigen_emit_byte(LGREATER_OP);
+	acpigen_emit_byte(LOCAL1_OP);
+	acpigen_emit_byte(ZERO_OP);
+
+	/* If (IBSY == 0) { Return (SUCCESS) } */
+	acpigen_write_if_lequal_namestr_int("IBSY", 0);
+	acpigen_set_package_element_int("RVAL", 0, PMC_IPC_SUCCESS);
+	acpigen_set_package_element_namestr("RVAL", 1, "IRB0");
+	acpigen_set_package_element_namestr("RVAL", 2, "IRB1");
+	acpigen_set_package_element_namestr("RVAL", 3, "IRB2");
+	acpigen_set_package_element_namestr("RVAL", 4, "IRB3");
+	acpigen_write_return_namestr("RVAL");
+	acpigen_pop_len();
+
+	/* If (IERR == 1) { Return (ERROR) } */
+	acpigen_write_if_lequal_namestr_int("IERR", 1);
+	acpigen_write_debug_string("IPCS ERROR");
+	acpigen_write_debug_namestr("IERC");
+	acpigen_set_package_element_int("RVAL", 0, PMC_IPC_ERROR);
+	acpigen_write_return_namestr("RVAL");
+	acpigen_pop_len();
+
+	/* Sleep (1) */
+	acpigen_write_sleep(1);
+	/* Decrement (Local1) */
+	acpigen_emit_byte(DECREMENT_OP);
+	acpigen_emit_byte(LOCAL1_OP);
+	acpigen_pop_len(); /* While */
+
+	/* Return (TIMEOUT) */
+	acpigen_write_debug_string("IPCS TIMEOUT");
+	acpigen_set_package_element_int("RVAL", 0, PMC_IPC_TIMEOUT);
+	acpigen_write_return_namestr("RVAL");
+
+	acpigen_pop_len(); /* Method */
+}
+
+void pmc_ipc_acpi_set_pci_clock(unsigned int pcie_rp, unsigned int clock_pin, bool enable)
+{
+	const uint32_t data[] = {
+		1 << clock_pin,			/* Clock pin to be modified */
+		(enable ? 1 : 0) << clock_pin,	/* Clock pin to set */
+		1 << pcie_rp,			/* PCIe root port to be modified */
+		(enable ? 1 : 0) << pcie_rp,	/* PCIe root port to set */
+	};
+	const char *method = acpi_device_path_join(pcidev_path_on_root(PCH_DEVFN_PMC), "IPCS");
+
+	if (!method) {
+		printk(BIOS_ERR, "%s: Unable to find PMC device IPCS method\n", __func__);
+		return;
+	}
+
+	/*
+	 * The PMC IPC mailbox method takes 7 arguments:
+	 *  IPCS (COMMAND, SUB_ID, SIZE, DATA0, DATA1, DATA2, DATA3)
+	 */
+	acpigen_emit_namestring(method);
+	acpigen_write_integer(PMC_IPC_CMD_ID_SET_PCIE_CLOCK);
+	acpigen_write_integer(0);
+	acpigen_write_integer(sizeof(data));
+	acpigen_write_dword(data[0]);
+	acpigen_write_dword(data[1]);
+	acpigen_write_dword(data[2]);
+	acpigen_write_dword(data[3]);
+}