hw/serial: ARM/arm64: Use MMIO at higher addresses

Using the UART devices at their legacy I/O addresses as set by IBM in
1981 was a kludge we used for simplicity on ARM platforms as well.
However this imposes problems due to their missing alignment and overlap
with the PCI I/O address space.

Now that we can switch a device easily between using ioports and MMIO,
let's move the UARTs out of the first 4K of memory on ARM platforms.

That should be transparent for well behaved guests, since the change is
naturally reflected in the device tree. Even "earlycon" keeps working,
as the stdout-path property is adjusted automatically.

People providing direct earlycon parameters via the command line need to
adjust it to: "earlycon=uart,mmio,0x1000000".

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Link: https://lore.kernel.org/r/20210315153350.19988-22-andre.przywara@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

2 files changed, 42 insertions, 19 deletions

diff --git a/arm/include/arm-common/kvm-arch.h b/arm/include/arm-common/kvm-arch.h
index a2e32953..bf34d742 100644
--- a/arm/include/arm-common/kvm-arch.h
+++ b/arm/include/arm-common/kvm-arch.h
@@ -13,8 +13,8 @@
  * 0      64K  16M     32M     48M            1GB       2GB
  * +-------+----+-------+-------+--------+-----+---------+---......
  * |  PCI  |////| plat  |       |        |     |         |
- * |  I/O  |////| MMIO  | Flash | virtio | GIC |   PCI   |  DRAM
- * | space |////|       |       |  MMIO  |     |  (AXI)  |
+ * |  I/O  |////| MMIO: | Flash | virtio | GIC |   PCI   |  DRAM
+ * | space |////| UART  |       |  MMIO  |     |  (AXI)  |
  * |       |////|       |       |        |     |         |
  * +-------+----+-------+-------+--------+-----+---------+---......
  */
@@ -28,6 +28,9 @@
 #define ARM_IOPORT_SIZE		(1U << 16)
 
 
+#define ARM_UART_MMIO_BASE	ARM_MMIO_AREA
+#define ARM_UART_MMIO_SIZE	0x10000
+
 #define KVM_FLASH_MMIO_BASE	(ARM_MMIO_AREA + 0x1000000)
 #define KVM_FLASH_MAX_SIZE	0x1000000
 
diff --git a/hw/serial.c b/hw/serial.c
index 16af493b..3d533623 100644
--- a/hw/serial.c
+++ b/hw/serial.c
@@ -13,6 +13,24 @@
 
 #include <pthread.h>
 
+#if defined(CONFIG_ARM) || defined(CONFIG_ARM64)
+#define serial_iobase(nr)	(ARM_UART_MMIO_BASE + (nr) * 0x1000)
+#define serial_irq(nr)		(32 + (nr))
+#define SERIAL8250_BUS_TYPE	DEVICE_BUS_MMIO
+#else
+#define serial_iobase_0		(KVM_IOPORT_AREA + 0x3f8)
+#define serial_iobase_1		(KVM_IOPORT_AREA + 0x2f8)
+#define serial_iobase_2		(KVM_IOPORT_AREA + 0x3e8)
+#define serial_iobase_3		(KVM_IOPORT_AREA + 0x2e8)
+#define serial_irq_0		4
+#define serial_irq_1		3
+#define serial_irq_2		4
+#define serial_irq_3		3
+#define serial_iobase(nr)	serial_iobase_##nr
+#define serial_irq(nr)		serial_irq_##nr
+#define SERIAL8250_BUS_TYPE	DEVICE_BUS_IOPORT
+#endif
+
 /*
  * This fakes a U6_16550A. The fifo len needs to be 64 as the kernel
  * expects that for autodetection.
@@ -27,7 +45,7 @@ struct serial8250_device {
 	struct mutex		mutex;
 	u8			id;
 
-	u16			iobase;
+	u32			iobase;
 	u8			irq;
 	u8			irq_state;
 	int			txcnt;
@@ -65,56 +83,56 @@ static struct serial8250_device devices[] = {
 	/* ttyS0 */
 	[0]	= {
 		.dev_hdr = {
-			.bus_type	= DEVICE_BUS_IOPORT,
+			.bus_type	= SERIAL8250_BUS_TYPE,
 			.data		= serial8250_generate_fdt_node,
 		},
 		.mutex			= MUTEX_INITIALIZER,
 
 		.id			= 0,
-		.iobase			= 0x3f8,
-		.irq			= 4,
+		.iobase			= serial_iobase(0),
+		.irq			= serial_irq(0),
 
 		SERIAL_REGS_SETTING
 	},
 	/* ttyS1 */
 	[1]	= {
 		.dev_hdr = {
-			.bus_type	= DEVICE_BUS_IOPORT,
+			.bus_type	= SERIAL8250_BUS_TYPE,
 			.data		= serial8250_generate_fdt_node,
 		},
 		.mutex			= MUTEX_INITIALIZER,
 
 		.id			= 1,
-		.iobase			= 0x2f8,
-		.irq			= 3,
+		.iobase			= serial_iobase(1),
+		.irq			= serial_irq(1),
 
 		SERIAL_REGS_SETTING
 	},
 	/* ttyS2 */
 	[2]	= {
 		.dev_hdr = {
-			.bus_type	= DEVICE_BUS_IOPORT,
+			.bus_type	= SERIAL8250_BUS_TYPE,
 			.data		= serial8250_generate_fdt_node,
 		},
 		.mutex			= MUTEX_INITIALIZER,
 
 		.id			= 2,
-		.iobase			= 0x3e8,
-		.irq			= 4,
+		.iobase			= serial_iobase(2),
+		.irq			= serial_irq(2),
 
 		SERIAL_REGS_SETTING
 	},
 	/* ttyS3 */
 	[3]	= {
 		.dev_hdr = {
-			.bus_type	= DEVICE_BUS_IOPORT,
+			.bus_type	= SERIAL8250_BUS_TYPE,
 			.data		= serial8250_generate_fdt_node,
 		},
 		.mutex			= MUTEX_INITIALIZER,
 
 		.id			= 3,
-		.iobase			= 0x2e8,
-		.irq			= 3,
+		.iobase			= serial_iobase(3),
+		.irq			= serial_irq(3),
 
 		SERIAL_REGS_SETTING
 	},
@@ -407,7 +425,7 @@ void serial8250_generate_fdt_node(void *fdt, struct device_header *dev_hdr,
 						     struct serial8250_device,
 						     dev_hdr);
 
-	u64 addr = KVM_IOPORT_AREA + dev->iobase;
+	u64 addr = dev->iobase;
 	u64 reg_prop[] = {
 		cpu_to_fdt64(addr),
 		cpu_to_fdt64(8),
@@ -440,7 +458,8 @@ static int serial8250__device_init(struct kvm *kvm,
 		return r;
 
 	ioport__map_irq(&dev->irq);
-	r = kvm__register_pio(kvm, dev->iobase, 8, serial8250_mmio, dev);
+	r = kvm__register_iotrap(kvm, dev->iobase, 8, serial8250_mmio, dev,
+				 SERIAL8250_BUS_TYPE);
 
 	return r;
 }
@@ -463,7 +482,7 @@ cleanup:
 	for (j = 0; j <= i; j++) {
 		struct serial8250_device *dev = &devices[j];
 
-		kvm__deregister_pio(kvm, dev->iobase);
+		kvm__deregister_iotrap(kvm, dev->iobase, SERIAL8250_BUS_TYPE);
 		device__unregister(&dev->dev_hdr);
 	}
 
@@ -479,7 +498,8 @@ int serial8250__exit(struct kvm *kvm)
 	for (i = 0; i < ARRAY_SIZE(devices); i++) {
 		struct serial8250_device *dev = &devices[i];
 
-		r = kvm__deregister_pio(kvm, dev->iobase);
+		r = kvm__deregister_iotrap(kvm, dev->iobase,
+					   SERIAL8250_BUS_TYPE);
 		if (r < 0)
 			return r;
 		device__unregister(&dev->dev_hdr);