Re: [kvm-unit-tests PATCH v2 06/23] arm/arm64: Add support for discovering the UART through ACPI

[Ricardo Koller <ricarkol@google.com>]

On Fri, May 06, 2022 at 09:55:48PM +0100, 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>
> ---
>  lib/acpi.h     | 25 +++++++++++++++++++++++++
>  lib/arm/io.c   | 21 +++++++++++++++++++--
>  lib/arm/psci.c |  4 +++-
>  3 files changed, 47 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/acpi.h b/lib/acpi.h
> index 139ccba..5213299 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();
>  }
>  
> diff --git a/lib/arm/psci.c b/lib/arm/psci.c
> index 0e96d19..afbc33d 100644
> --- a/lib/arm/psci.c
> +++ b/lib/arm/psci.c
> @@ -80,9 +80,11 @@ static void psci_set_conduit_fdt(void)
>  static void psci_set_conduit_acpi(void)
>  {
>  	struct acpi_table_fadt *fadt = find_acpi_table_addr(FACP_SIGNATURE);
> +
>  	assert_msg(fadt, "Unable to find ACPI FADT");
>  	assert_msg(fadt->arm_boot_flags & ACPI_FADT_PSCI_COMPLIANT,
> -		   "PSCI is not supported in this platfrom");
> +		   "PSCI is not supported in this platform");
> +
>  	if (fadt->arm_boot_flags & ACPI_FADT_PSCI_USE_HVC)
>  		psci_invoke = psci_invoke_hvc;
>  	else
> -- 
> 2.25.1
>

Reviewed-by: Ricardo Koller <ricarkol@google.com>