diff options
Diffstat (limited to 'arch/mips/alchemy/common/clocks.c')
| -rw-r--r-- | arch/mips/alchemy/common/clocks.c | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/arch/mips/alchemy/common/clocks.c b/arch/mips/alchemy/common/clocks.c index a8170fda4932..d8991854530e 100644 --- a/arch/mips/alchemy/common/clocks.c +++ b/arch/mips/alchemy/common/clocks.c @@ -27,11 +27,21 @@ */ #include <linux/module.h> +#include <linux/spinlock.h> +#include <asm/time.h> #include <asm/mach-au1x00/au1000.h> +/* + * I haven't found anyone that doesn't use a 12 MHz source clock, + * but just in case..... + */ +#define AU1000_SRC_CLK 12000000 + static unsigned int au1x00_clock; /* Hz */ static unsigned long uart_baud_base; +static DEFINE_SPINLOCK(time_lock); + /* * Set the au1000_clock */ @@ -60,3 +70,47 @@ void set_au1x00_uart_baud_base(unsigned long new_baud_base) { uart_baud_base = new_baud_base; } + +/* + * We read the real processor speed from the PLL. This is important + * because it is more accurate than computing it from the 32 KHz + * counter, if it exists. If we don't have an accurate processor + * speed, all of the peripherals that derive their clocks based on + * this advertised speed will introduce error and sometimes not work + * properly. This function is futher convoluted to still allow configurations + * to do that in case they have really, really old silicon with a + * write-only PLL register. -- Dan + */ +unsigned long au1xxx_calc_clock(void) +{ + unsigned long cpu_speed; + unsigned long flags; + + spin_lock_irqsave(&time_lock, flags); + + /* + * On early Au1000, sys_cpupll was write-only. Since these + * silicon versions of Au1000 are not sold by AMD, we don't bend + * over backwards trying to determine the frequency. + */ + if (au1xxx_cpu_has_pll_wo()) +#ifdef CONFIG_SOC_AU1000_FREQUENCY + cpu_speed = CONFIG_SOC_AU1000_FREQUENCY; +#else + cpu_speed = 396000000; +#endif + else + cpu_speed = (au_readl(SYS_CPUPLL) & 0x0000003f) * AU1000_SRC_CLK; + + /* On Alchemy CPU:counter ratio is 1:1 */ + mips_hpt_frequency = cpu_speed; + /* Equation: Baudrate = CPU / (SD * 2 * CLKDIV * 16) */ + set_au1x00_uart_baud_base(cpu_speed / (2 * ((int)(au_readl(SYS_POWERCTRL) + & 0x03) + 2) * 16)); + + spin_unlock_irqrestore(&time_lock, flags); + + set_au1x00_speed(cpu_speed); + + return cpu_speed; +} |