[Xen-devel] [PATCH v4] ns16550: Add ACPI support for ARM only

[Wei Xu <xuwei5@xxxxxxxxxxxxx>]

Parse the ACPI SPCR table and initialize the 16550 compatible serial port
for ARM only. Currently we only support one UART on ARM. Some fields
which we do not care yet on ARM are ignored.

Signed-off-by: Wei Xu <xuwei5@xxxxxxxxxxxxx>

---
Changes in v4:
- change the print when the serial port address is 0
- check the serial port address space id before initializing
- change the comment for the ignored PCIe fields

Changes in v3:
- address the code style comments from Jan
- use container_of to do cast
- list all fields we ignored
- check the console redirection is disabled or not before init the uart
- init the uart io_size and width via spcr->serial_port

Changes in v2:
- improve commit message
- remove the spcr initialization
- add comments for the uart initialization and configuration
- adjust the code style issue
- limit the code only built on ACPI and ARM
---
 xen/drivers/char/ns16550.c | 79 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)

diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c
index aa87c57..dc8ac4c 100644
--- a/xen/drivers/char/ns16550.c
+++ b/xen/drivers/char/ns16550.c
@@ -1620,6 +1620,85 @@ DT_DEVICE_START(ns16550, "NS16550 UART", DEVICE_SERIAL)
 DT_DEVICE_END

 #endif /* HAS_DEVICE_TREE */
+
+#if defined(CONFIG_ACPI) && defined(CONFIG_ARM)
+#include <xen/acpi.h>
+
+static int __init ns16550_acpi_uart_init(const void *data)
+{
+    struct acpi_table_header *table;
+    struct acpi_table_spcr *spcr;
+    acpi_status status;
+    /*
+     * Same as the DT part.
+     * Only support one UART on ARM which happen to be ns16550_com[0].
+     */
+    struct ns16550 *uart = &ns16550_com[0];
+
+    status = acpi_get_table(ACPI_SIG_SPCR, 0, &table);
+    if ( ACPI_FAILURE(status) )
+    {
+        printk("ns16550: Failed to get SPCR table\n");
+        return -EINVAL;
+    }
+
+    spcr = container_of(table, struct acpi_table_spcr, header);
+
+    /*
+     * The serial port address may be 0 for example
+     * if the console redirection is disabled.
+     */
+    if ( unlikely(!spcr->serial_port.address) )
+    {
+        printk("ns16550: Console redirection is disabled\n");
+        return -EINVAL;
+    }
+
+    if ( unlikely(spcr->serial_port.space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY) )
+    {
+        printk("ns16550: Address space type is not mmio\n");
+        return -EINVAL;
+    }
+
+    ns16550_init_common(uart);
+
+    /*
+     * The baud rate is pre-configured by the firmware.
+     * And currently the ACPI part is only targeting ARM so the flow_control
+     * field and all PCI related ones which we do not care yet are ignored.
+     */
+    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->io_size = spcr->serial_port.bit_width;
+    uart->reg_shift = spcr->serial_port.bit_offset;
+    uart->reg_width = spcr->serial_port.access_width;
+
+    /* The trigger/polarity information is not available in spcr. */
+    irq_set_type(spcr->interrupt, IRQ_TYPE_LEVEL_HIGH);
+    uart->irq = spcr->interrupt;
+
+    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;
+
+    /* Register with generic serial driver. */
+    serial_register_uart(SERHND_DTUART, &ns16550_driver, uart);
+
+    return 0;
+}
+
+ACPI_DEVICE_START(ans16550, "NS16550 UART", DEVICE_SERIAL)
+    .class_type = ACPI_DBG2_16550_COMPATIBLE,
+    .init = ns16550_acpi_uart_init,
+ACPI_DEVICE_END
+
+#endif /* CONFIG_ACPI && CONFIG_ARM */
+
 /*
  * Local variables:
  * mode: C
-- 
2.8.1


.


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