[PATCH] bsp/imx: Fix system counter init for imx6

[Christian MAUDERER]

Hello,

I want to backport that patch to RTEMS 5 too because this problem 
occurred multiple times on the mailing list. If that is OK I'll create a 
separate ticket for RTEMS 5 that describes that problem. For RTEMS 6 it 
should finally be the last step to closing the "add i.MX6UL" ticket.

Best regards

Christian

Am 18.01.21 um 10:02 schrieb Christian Mauderer:
> For i.MX7 U-Boot initializes the system counter. On i.MX6 Barebox is
> often used which doesn't initialize the counter. With this patch, we try
> to auto-detect whether the counter is initialized or not and do the
> initialization ourself if necessary.
> 
> Closes #3869
> ---
>   bsps/arm/imx/start/bspstart.c | 61 ++++++++++++++++++++++++++++++++++-
>   1 file changed, 60 insertions(+), 1 deletion(-)
> 
> diff --git a/bsps/arm/imx/start/bspstart.c b/bsps/arm/imx/start/bspstart.c
> index 9f610d1ff5..238bc2bd28 100644
> --- a/bsps/arm/imx/start/bspstart.c
> +++ b/bsps/arm/imx/start/bspstart.c
> @@ -19,6 +19,7 @@
>   #include <bsp/irq-generic.h>
>   #include <bsp/linker-symbols.h>
>   #include <dev/clock/arm-generic-timer.h>
> +#include <libcpu/arm-cp15.h>
>   
>   #include <libfdt.h>
>   
> @@ -59,6 +60,60 @@ uint32_t bsp_fdt_map_intr(const uint32_t *intr, size_t icells)
>     return intr[1] + MAGIC_IRQ_OFFSET;
>   }
>   
> +static bool imx_is_imx6(const void *fdt)
> +{
> +  /*
> +   * At the moment: Check for some compatible strings that should be there
> +   * somewhere in every fdt.
> +   *
> +   * FIXME: It would be nice if some CPU-ID could be used instead. But I didn't
> +   * find one.
> +   */
> +  int node;
> +
> +  node = fdt_node_offset_by_compatible(fdt, -1, "fsl,imx6ul");
> +  if (node >= 0) {
> +    return true;
> +  }
> +
> +  node = fdt_node_offset_by_compatible(fdt, -1, "fsl,imx6ull");
> +  if (node >= 0) {
> +    return true;
> +  }
> +
> +  return false;
> +}
> +
> +#define SYSCNT_CNTCR          (0x0)
> +#define SYSCNT_CNTCR_ENABLE   (1 << 0)
> +#define SYSCNT_CNTCR_HDBG     (1 << 1)
> +#define SYSCNT_CNTCR_FCREQ(n) (1 << (8 + (n)))
> +#define SYSCNT_CNTFID(n)      (0x20 + 4 * (n))
> +
> +static uint32_t imx_syscnt_enable_and_return_frequency(const void *fdt)
> +{
> +  uint32_t freq;
> +  volatile void *syscnt_base;
> +
> +  /* That's not in the usual FDTs. Sorry for falling back to a magic value. */
> +  if (imx_is_imx6(fdt)) {
> +    syscnt_base = (void *)0x021dc000;
> +  } else {
> +    syscnt_base = (void *)0x306c0000;
> +  }
> +
> +  freq = *(uint32_t *)(syscnt_base + SYSCNT_CNTFID(0));
> +
> +  arm_cp15_set_counter_frequency(freq);
> +
> +  *(uint32_t *)(syscnt_base + SYSCNT_CNTCR) =
> +    SYSCNT_CNTCR_ENABLE |
> +    SYSCNT_CNTCR_HDBG |
> +    SYSCNT_CNTCR_FCREQ(0);
> +
> +  return freq;
> +}
> +
>   void arm_generic_timer_get_config(
>     uint32_t *frequency,
>     uint32_t *irq
> @@ -76,7 +131,11 @@ void arm_generic_timer_get_config(
>     if (val != NULL && len >= 4) {
>       *frequency = fdt32_to_cpu(val[0]);
>     } else {
> -    bsp_fatal(IMX_FATAL_GENERIC_TIMER_FREQUENCY);
> +    /*
> +     * Normally clock-frequency would be provided by the boot loader. If it
> +     * didn't add one, we have to initialize the system counter ourself.
> +     */
> +    *frequency = imx_syscnt_enable_and_return_frequency(fdt);
>     }
>   
>     /* FIXME: Figure out how Linux gets a proper IRQ number */
> 

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