Re: [kvm-unit-tests PATCH v5 12/29] arm64: Add support for discovering the UART through ACPI

[Shaoqin Huang <shahuang@redhat.com>]

On 4/28/23 20:03, Nikos Nikoleris wrote:
> 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@arm.com>
> Reviewed-by: Andrew Jones <drjones@redhat.com>
> Reviewed-by: Ricardo Koller <ricarkol@google.com>
Reviewed-by: Shaoqin Huang <shahuang@redhat.com>
> ---
>   lib/acpi.h   | 25 +++++++++++++++++++++++++
>   lib/arm/io.c | 34 +++++++++++++++++++++++++++++-----
>   2 files changed, 54 insertions(+), 5 deletions(-)
> 
> diff --git a/lib/acpi.h b/lib/acpi.h
> index ef4a8e1d..54ed9ef7 100644
> --- a/lib/acpi.h
> +++ b/lib/acpi.h
> @@ -17,6 +17,7 @@
>   #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) \
>   	(((uint64_t)(ACPI_SIGNATURE(c1, c2, c3, c4))) |	     \
> @@ -145,6 +146,30 @@ struct acpi_table_facs_rev1 {
>   	u8 reserved3[40];	/* Reserved - must be zero */
>   };
>   
> +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;
> +};
> +
>   #pragma pack(0)
>   
>   void set_efi_rsdp(struct acpi_table_rsdp *rsdp);
> diff --git a/lib/arm/io.c b/lib/arm/io.c
> index 343e1082..19f93490 100644
> --- a/lib/arm/io.c
> +++ b/lib/arm/io.c
> @@ -29,7 +29,7 @@ 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
> @@ -65,17 +65,41 @@ static void uart0_init(void)
>   	}
>   
>   	uart0_base = ioremap(base.addr, base.size);
> +}
> +
> +#ifdef CONFIG_EFI
> +
> +#include <acpi.h>
> +
> +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);
> +}
> +#else
> +
> +static void uart0_init_acpi(void)
> +{
> +	assert_msg(false, "ACPI not available");
> +}
> +
> +#endif
> +
> +void io_init(void)
> +{
> +	if (dt_available())
> +		uart0_init_fdt();
> +	else
> +		uart0_init_acpi();
>   
>   	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();
>   	chr_testdev_init();
>   }
>   

-- 
Shaoqin