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| author | Jonathan Kimmitt <jonathan@kimmitt.uk> | 2019-11-06 17:43:09 +0000 |
|---|---|---|
| committer | Andrew Waterman <andrew@sifive.com> | 2019-11-06 09:43:09 -0800 |
| commit | 14e87d2dd250b0efb5e9fb19ab279ccf1ccbdbd7 (patch) | |
| tree | 981f33c25b55b354fdfe01f9977951e9fd0faee4 | |
| parent | b1bdf5bb995ada25f4855279e90ac2c54c7162fa (diff) | |
| download | riscv-pk-14e87d2dd250b0efb5e9fb19ab279ccf1ccbdbd7.zip riscv-pk-14e87d2dd250b0efb5e9fb19ab279ccf1ccbdbd7.tar.gz riscv-pk-14e87d2dd250b0efb5e9fb19ab279ccf1ccbdbd7.tar.bz2 | |
Support a subset of 16750 functionality, and improve baud rate selection (#182)
| -rw-r--r-- | machine/uart16550.c | 18 |
1 files changed, 15 insertions, 3 deletions
diff --git a/machine/uart16550.c b/machine/uart16550.c index 44685eb..f4fbbee 100644 --- a/machine/uart16550.c +++ b/machine/uart16550.c @@ -25,7 +25,10 @@ static uint32_t uart16550_clock = 1843200; // a "common" base clock #define UART_REG_STATUS_RX 0x01 #define UART_REG_STATUS_TX 0x20 +// We cannot use the word DEFAULT for a parameter that cannot be overridden due to -Werror +#ifndef UART_DEFAULT_BAUD #define UART_DEFAULT_BAUD 38400 +#endif void uart16550_putchar(uint8_t ch) { @@ -47,18 +50,21 @@ struct uart16550_scan uint32_t reg_offset; uint32_t reg_shift; uint32_t clock_freq; + uint32_t baud; }; static void uart16550_open(const struct fdt_scan_node *node, void *extra) { struct uart16550_scan *scan = (struct uart16550_scan *)extra; memset(scan, 0, sizeof(*scan)); + scan->baud = UART_DEFAULT_BAUD; } static void uart16550_prop(const struct fdt_scan_prop *prop, void *extra) { struct uart16550_scan *scan = (struct uart16550_scan *)extra; - if (!strcmp(prop->name, "compatible") && fdt_string_list_index(prop, "ns16550a") != -1) { + // For the purposes of the boot loader, the 16750 is a superset of what 16550a provides + if (!strcmp(prop->name, "compatible") && ((fdt_string_list_index(prop, "ns16550a") != -1) || (fdt_string_list_index(prop, "ns16750") != -1))) { scan->compat = 1; } else if (!strcmp(prop->name, "reg")) { fdt_get_address(prop->node->parent, prop->value, &scan->reg); @@ -66,6 +72,9 @@ static void uart16550_prop(const struct fdt_scan_prop *prop, void *extra) scan->reg_shift = fdt_get_value(prop, 0); } else if (!strcmp(prop->name, "reg-offset")) { scan->reg_offset = fdt_get_value(prop, 0); + } else if (!strcmp(prop->name, "current-speed")) { + // This is the property that Linux uses + scan->baud = fdt_get_value(prop, 0); } else if (!strcmp(prop->name, "clock-frequency")) { scan->clock_freq = fdt_get_value(prop, 0); } @@ -81,8 +90,11 @@ static void uart16550_done(const struct fdt_scan_node *node, void *extra) uart16550_clock = scan->clock_freq; // if device tree doesn't supply a clock, fallback to default clock of 1843200 - uint32_t divisor = uart16550_clock / (16 * UART_DEFAULT_BAUD); - assert (divisor < 0x10000u); + // Check for divide by zero + uint32_t divisor = uart16550_clock / (16 * (scan->baud ? scan->baud : UART_DEFAULT_BAUD)); + // If the divisor is out of range, don't assert, set the rate back to the default + if (divisor >= 0x10000u) + divisor = uart16550_clock / (16 * UART_DEFAULT_BAUD); uart16550 = (void*)((uintptr_t)scan->reg + scan->reg_offset); uart16550_reg_shift = scan->reg_shift; |