[kvm-unit-tests PATCH 06/23] arm/arm64: Add support for discovering the UART through ACPI

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In systems with ACPI support and when a DT is not provided, we can use
the SPCR to discover the serial port address range. This change
implements this but retains the default behavior; we check if a valid
DT is provided, if not, we try to discover the UART using ACPI.

Signed-off-by: Nikos Nikoleris <nikos.nikoleris@xxxxxxx>
---
 lib/acpi.h   | 25 +++++++++++++++++++++++++
 lib/arm/io.c | 21 +++++++++++++++++++--
 2 files changed, 44 insertions(+), 2 deletions(-)

diff --git a/lib/acpi.h b/lib/acpi.h
index 40392e3..0611cdf 100644
--- a/lib/acpi.h
+++ b/lib/acpi.h
@@ -16,6 +16,7 @@
 #define XSDT_SIGNATURE ACPI_SIGNATURE('X','S','D','T')
 #define FACP_SIGNATURE ACPI_SIGNATURE('F','A','C','P')
 #define FACS_SIGNATURE ACPI_SIGNATURE('F','A','C','S')
+#define SPCR_SIGNATURE ACPI_SIGNATURE('S','P','C','R')
 
 
 #define ACPI_SIGNATURE_8BYTE(c1, c2, c3, c4, c5, c6, c7, c8) \
@@ -147,6 +148,30 @@ struct facs_descriptor_rev1
     u8  reserved3 [40];         /* Reserved - must be zero */
 } __attribute__ ((packed));
 
+struct spcr_descriptor {
+    ACPI_TABLE_HEADER_DEF   /* ACPI common table header */
+    u8 interface_type;      /* 0=full 16550, 1=subset of 16550 */
+    u8 reserved[3];
+    struct acpi_generic_address serial_port;
+    u8 interrupt_type;
+    u8 pc_interrupt;
+    u32 interrupt;
+    u8 baud_rate;
+    u8 parity;
+    u8 stop_bits;
+    u8 flow_control;
+    u8 terminal_type;
+    u8 reserved1;
+    u16 pci_device_id;
+    u16 pci_vendor_id;
+    u8 pci_bus;
+    u8 pci_device;
+    u8 pci_function;
+    u32 pci_flags;
+    u8 pci_segment;
+    u32 reserved2;
+} __attribute__ ((packed));
+
 void set_efi_rsdp(struct rsdp_descriptor *rsdp);
 void* find_acpi_table_addr(u32 sig);
 
diff --git a/lib/arm/io.c b/lib/arm/io.c
index 343e108..893bdfc 100644
--- a/lib/arm/io.c
+++ b/lib/arm/io.c
@@ -8,6 +8,7 @@
  *
  * This work is licensed under the terms of the GNU LGPL, version 2.
  */
+#include <acpi.h>
 #include <libcflat.h>
 #include <devicetree.h>
 #include <chr-testdev.h>
@@ -29,7 +30,7 @@ static struct spinlock uart_lock;
 #define UART_EARLY_BASE (u8 *)(unsigned long)CONFIG_UART_EARLY_BASE
 static volatile u8 *uart0_base = UART_EARLY_BASE;
 
-static void uart0_init(void)
+static void uart0_init_fdt(void)
 {
 	/*
 	 * kvm-unit-tests uses the uart only for output. Both uart models have
@@ -73,9 +74,25 @@ static void uart0_init(void)
 	}
 }
 
+static void uart0_init_acpi(void)
+{
+	struct spcr_descriptor *spcr = find_acpi_table_addr(SPCR_SIGNATURE);
+	assert_msg(spcr, "Unable to find ACPI SPCR");
+	uart0_base = ioremap(spcr->serial_port.address, spcr->serial_port.bit_width);
+
+	if (uart0_base != UART_EARLY_BASE) {
+		printf("WARNING: early print support may not work. "
+		       "Found uart at %p, but early base is %p.\n",
+			uart0_base, UART_EARLY_BASE);
+	}
+}
+
 void io_init(void)
 {
-	uart0_init();
+	if (dt_available())
+		uart0_init_fdt();
+	else
+		uart0_init_acpi();
 	chr_testdev_init();
 }
 
-- 
2.25.1




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