[Xen-devel] [PATCH 1/2 v2] xen: Add support for initializing 16550 UART using ACPI

[Bhupinder Thakur <bhupinder.thakur@xxxxxxxxxx>]

Currently, Xen supports only DT based initialization of 16550 UART.
This patch adds support for initializing 16550 UART using ACPI SPCR table.

This patch also makes the uart initialization code common between DT and
ACPI based initialization.

Signed-off-by: Bhupinder Thakur <bhupinder.thakur@xxxxxxxxxx>
---
TBD:
There was one review comment from Julien about how the uart->io_size is being 
calculated. Currently, I am calulating the io_size based on address of the last
UART register. 

pci_uart_config also calcualates the uart->io_size like this:

uart->io_size = max(8U << param->reg_shift,
                                 param->uart_offset);

I am not sure whether we can use similar logic for calculating uart->io_size.

Changes since v1:
- Reused common code between DT and ACPI based initializations

CC: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
CC: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
CC: Jan Beulich <jbeulich@xxxxxxxx>
CC: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Tim Deegan <tim@xxxxxxx>
CC: Wei Liu <wei.liu2@xxxxxxxxxx>
CC: Julien Grall <julien.grall@xxxxxxx>

 xen/drivers/char/ns16550.c  | 132 ++++++++++++++++++++++++++++++++++++++++----
 xen/include/xen/8250-uart.h |   1 +
 2 files changed, 121 insertions(+), 12 deletions(-)

diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c
index e0f8199..cf42fce 100644
--- a/xen/drivers/char/ns16550.c
+++ b/xen/drivers/char/ns16550.c
@@ -1463,18 +1463,13 @@ void __init ns16550_init(int index, struct 
ns16550_defaults *defaults)
 }
 
 #ifdef CONFIG_HAS_DEVICE_TREE
-static int __init ns16550_uart_dt_init(struct dt_device_node *dev,
-                                       const void *data)
+static int ns16550_init_dt(struct ns16550 *uart,
+                           const struct dt_device_node *dev)
 {
-    struct ns16550 *uart;
-    int res;
+    int res = 0;
     u32 reg_shift, reg_width;
     u64 io_size;
 
-    uart = &ns16550_com[0];
-
-    ns16550_init_common(uart);
-
     uart->baud      = BAUD_AUTO;
     uart->data_bits = 8;
     uart->parity    = UART_PARITY_NONE;
@@ -1510,18 +1505,103 @@ static int __init ns16550_uart_dt_init(struct 
dt_device_node *dev,
 
     uart->dw_usr_bsy = dt_device_is_compatible(dev, "snps,dw-apb-uart");
 
+    return res;
+}
+#else
+static int ns16550_init_dt(struct ns16550 *uart,
+                           const struct dt_device_node *dev)
+{
+    return -EINVAL;
+}
+#endif
+
+#ifdef CONFIG_ACPI
+#include <xen/acpi.h>
+static int ns16550_init_acpi(struct ns16550 *uart,
+                             const void *data)
+{
+    struct acpi_table_spcr *spcr = NULL;
+    int status = 0;
+
+    status = acpi_get_table(ACPI_SIG_SPCR, 0,
+                            (struct acpi_table_header **)&spcr);
+
+    if ( ACPI_FAILURE(status) )
+    {
+        printk("ns16550: Failed to get SPCR table\n");
+        return -EINVAL;
+    }
+
+    uart->baud      = BAUD_AUTO;
+    uart->data_bits = 8;
+    uart->parity    = spcr->parity;
+    uart->stop_bits = spcr->stop_bits;
+    uart->io_base = spcr->serial_port.address;
+    uart->irq = spcr->interrupt;
+    uart->reg_width = spcr->serial_port.bit_width / 8;
+    uart->reg_shift = 0;
+    uart->io_size = UART_MAX_REG << uart->reg_shift;
+
+    irq_set_type(spcr->interrupt, spcr->interrupt_type);
+
+    return 0;
+}
+#else
+static int ns16550_init_acpi(struct ns16550 *uart,
+                             const void *data)
+{
+    return -EINVAL;
+}
+#endif
+
+static int ns16550_uart_init(struct ns16550 **puart,
+                             const void *data, bool acpi)
+{
+    struct ns16550 *uart = &ns16550_com[0];
+
+    *puart = uart;
+
+    ns16550_init_common(uart);
+
+    return ( acpi ) ? ns16550_init_acpi(uart, data)
+                    : ns16550_init_dt(uart, data);
+}
+
+static void ns16550_vuart_init(struct ns16550 *uart)
+{
+#ifdef CONFIG_ARM
     uart->vuart.base_addr = uart->io_base;
     uart->vuart.size = uart->io_size;
-    uart->vuart.data_off = UART_THR <<uart->reg_shift;
-    uart->vuart.status_off = UART_LSR<<uart->reg_shift;
-    uart->vuart.status = UART_LSR_THRE|UART_LSR_TEMT;
+    uart->vuart.data_off = UART_THR << uart->reg_shift;
+    uart->vuart.status_off = UART_LSR << uart->reg_shift;
+    uart->vuart.status = UART_LSR_THRE | UART_LSR_TEMT;
+#endif
+}
 
+static void ns16550_register_uart(struct ns16550 *uart)
+{
     /* Register with generic serial driver. */
     serial_register_uart(uart - ns16550_com, &ns16550_driver, uart);
+}
+
+#ifdef CONFIG_HAS_DEVICE_TREE
+static int __init ns16550_uart_dt_init(struct dt_device_node *dev,
+                                       const void *data)
+{
+    struct ns16550 *uart;
+    int ret = 0;
+
+    ret = ns16550_uart_init(&uart, dev, false);
+    if ( ret )
+        return ret;
+
+    ns16550_vuart_init(uart);
+
+    ns16550_register_uart(uart);
 
     dt_device_set_used_by(dev, DOMID_XEN);
 
-    return 0;
+    return ret;
 }
 
 static const struct dt_device_match ns16550_dt_match[] __initconst =
@@ -1538,6 +1618,34 @@ DT_DEVICE_START(ns16550, "NS16550 UART", DEVICE_SERIAL)
 DT_DEVICE_END
 
 #endif /* HAS_DEVICE_TREE */
+
+#ifdef CONFIG_ACPI
+static int __init ns16550_acpi_uart_init(const void *data)
+{
+    struct ns16550 *uart;
+    int ret = 0;
+
+    ret = ns16550_uart_init(&uart, data, true);
+    if ( ret )
+        return ret;
+
+    ns16550_vuart_init(uart);
+
+    ns16550_register_uart(uart);
+
+    return ret;
+}
+
+ACPI_DEVICE_START(ns16550c, "16550 COMPAT UART", DEVICE_SERIAL)
+        .class_type = ACPI_DBG2_16550_COMPATIBLE,
+        .init = ns16550_acpi_uart_init,
+ACPI_DEVICE_END
+ACPI_DEVICE_START(ns16550s, "16550 SUBSET UART", DEVICE_SERIAL)
+        .class_type = ACPI_DBG2_16550_SUBSET,
+        .init = ns16550_acpi_uart_init,
+ACPI_DEVICE_END
+
+#endif
 /*
  * Local variables:
  * mode: C
diff --git a/xen/include/xen/8250-uart.h b/xen/include/xen/8250-uart.h
index 5c3bac3..1b3e137 100644
--- a/xen/include/xen/8250-uart.h
+++ b/xen/include/xen/8250-uart.h
@@ -35,6 +35,7 @@
 #define UART_USR          0x1f    /* Status register (DW) */
 #define UART_DLL          0x00    /* divisor latch (ls) (DLAB=1) */
 #define UART_DLM          0x01    /* divisor latch (ms) (DLAB=1) */
+#define UART_MAX_REG      (UART_USR + 1)
 
 /* Interrupt Enable Register */
 #define UART_IER_ERDAI    0x01    /* rx data recv'd       */
-- 
2.7.4


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