Re: [Minios-devel] [UNIKRAFT PATCHv6 37/37] plat/common: Get arch_timer clock frequency from DT for Arm

[Simon Kuenzer <simon.kuenzer@xxxxxxxxx>]

Reviewed-by: Simon Kuenzer <simon.kuenzer@xxxxxxxxx>

On 14.09.2018 09:57, Wei Chen wrote:
> On a few platforms the frequency is not configured correctly
> by the firmware. A property in the DT (clock-frequency) has
> been introduced to workaround those firmware. So, we will try
> to get clock-frequency from DT first, if failed we will read
> the register directly.
>
> Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
> ---
>   plat/common/arm/time.c | 36 +++++++++++++++++++++++++++++++++++-
>   1 file changed, 35 insertions(+), 1 deletion(-)
>
> diff --git a/plat/common/arm/time.c b/plat/common/arm/time.c
> index 8457511..c309b03 100644
> --- a/plat/common/arm/time.c
> +++ b/plat/common/arm/time.c
> @@ -32,6 +32,7 @@
>    * THIS HEADER MAY NOT BE EXTRACTED OR MODIFIED IN ANY WAY.
>    */
>   #include <stdlib.h>
> +#include <libfdt.h>
>   #include <uk/assert.h>
>   #include <uk/plat/time.h>
>   #include <uk/plat/irq.h>
> @@ -40,6 +41,7 @@
>   
>   static uint64_t boot_ticks;
>   static uint32_t counter_freq;
> +extern void *_libkvmplat_dtb;
>   
>   /*
>    * Shift factor for counter scaling multiplier; referred to as S in the
> @@ -58,8 +60,40 @@ static inline uint64_t ticks_to_ns(uint64_t ticks)
>         return (ns_per_tick * ticks) >> counter_shift;
>   }
>   
> -static inline uint32_t get_counter_frequency(void)
> +/*
> + * On a few platforms the frequency is not configured correctly
> + * by the firmware. A property in the DT (clock-frequency) has
> + * been introduced to workaround those firmware. So, we will try
> + * to get clock-frequency from DT first, if failed we will read
> + * the register directly.
> + */
> +static uint32_t get_counter_frequency(void)
>   {
> +       int fdt_archtimer, len;
> +       const uint64_t *fdt_freq;
> +
> +       /* Try to find arm,armv8-timer first */
> +       fdt_archtimer = fdt_node_offset_by_compatible(_libkvmplat_dtb,
> +                                               -1, "arm,armv8-timer");
> +       /* If failed, try to find arm,armv7-timer */
> +       if (fdt_archtimer < 0)
> +               fdt_archtimer = fdt_node_offset_by_compatible(_libkvmplat_dtb,
> +                                                       -1, "arm,armv7-timer");
> +       /* DT doesn't provide arch timer information */
> +       if (fdt_archtimer < 0)
> +               goto endnofreq;
> +
> +       fdt_freq = fdt_getprop(_libkvmplat_dtb,
> +                       fdt_archtimer, "clock-frequency", &len);
> +       if (!fdt_freq || (len <= 0)) {
> +               uk_printd(DLVL_INFO,
> +               "No clock-frequency found, reading from register directly.\n");
> +               goto endnofreq;
> +       }
> +
> +       return fdt32_to_cpu(fdt_freq[0]);
> +
> +endnofreq:
>         return SYSREG_READ32(cntfrq_el0);
>   }
>   
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