diff options
Diffstat (limited to 'src/drivers/uart/oxpcie_early.c')
| -rw-r--r-- | src/drivers/uart/oxpcie_early.c | 40 |
1 files changed, 37 insertions, 3 deletions
diff --git a/src/drivers/uart/oxpcie_early.c b/src/drivers/uart/oxpcie_early.c index 2cbc8c7948..206f54d1a5 100644 --- a/src/drivers/uart/oxpcie_early.c +++ b/src/drivers/uart/oxpcie_early.c @@ -5,8 +5,9 @@ #include <device/pci_ops.h> #include <console/uart.h> #include <device/pci.h> +#include "uart8250reg.h" -static unsigned int oxpcie_present; +static int oxpcie_present; static DEVTREE_CONST u32 uart0_base = CONFIG_EARLY_PCI_MMIO_BASE + 0x1000; int pci_early_device_probe(u8 bus, u8 dev, u32 mmio_base) @@ -49,9 +50,42 @@ int pci_early_device_probe(u8 bus, u8 dev, u32 mmio_base) return 0; } -static int oxpcie_uart_active(void) +/* + * Stages that do not call pci_early_device_probe() identify an + * enabled UART with a test read. Since PCI bus enumeration + * has not happened PCI configuration register access is not + * possible here. + */ +static int uart_presence(uintptr_t base) { - return oxpcie_present; + /* LCR has no side-effects on reads. */ + const u8 reg = UART8250_LCR; + u8 val; + + if (CONFIG(DRIVERS_UART_8250MEM_32)) + val = read32p(base + 4 * reg) & 0xff; + else + val = read8p(base + reg); + + if (val == 0xff) + return -1; + + /* Something decoded MMIO read, assume it was the UART. */ + return 1; +} + +static bool oxpcie_uart_active(void) +{ + if (oxpcie_present == 0) + oxpcie_present = uart_presence(uart0_base); + + if (oxpcie_present > 0) + return true; + if (oxpcie_present < 0) + return false; + + /* not reached */ + return false; } uintptr_t uart_platform_base(unsigned int idx) |