[U-Boot] [PATCH 062/126] x86: Add a function to set variable MTRRs

[Bin Meng]

On Wed, Sep 25, 2019 at 10:58 PM Simon Glass <sjg at chromium.org> wrote:
>
> Normally U-Boot handles MTRRs through an add/commit process which
> overwrites all MTRRs. But in very early boot it is not desirable to clear
> the existing MTRRs since they may be in use and it can cause a hang.
>
> Add a new mtrr_set_next_var() function which sets up the next available
> MTRR to the required region.
>
> Signed-off-by: Simon Glass <sjg at chromium.org>
> ---
>
>  arch/x86/cpu/mtrr.c         | 38 +++++++++++++++++++++++++++++++++++++
>  arch/x86/include/asm/mtrr.h | 12 ++++++++++++
>  2 files changed, 50 insertions(+)
>
> diff --git a/arch/x86/cpu/mtrr.c b/arch/x86/cpu/mtrr.c
> index 6218d149e30..1a7c292fa8b 100644
> --- a/arch/x86/cpu/mtrr.c
> +++ b/arch/x86/cpu/mtrr.c
> @@ -112,3 +112,41 @@ int mtrr_add_request(int type, uint64_t start, uint64_t size)
>
>         return 0;
>  }
> +
> +static int get_var_mtrr_count(void)
> +{
> +       return msr_read(MSR_MTRR_CAP_MSR).lo & MSR_MTRR_CAP_VCNT;
> +}
> +
> +static int get_free_var_mtrr(void)
> +{
> +       struct msr_t maskm;
> +       int vcnt;
> +       int i;
> +
> +       vcnt = get_var_mtrr_count();
> +
> +       /* Identify the first var mtrr which is not valid */
> +       for (i = 0; i < vcnt; i++) {
> +               maskm = msr_read(MTRR_PHYS_MASK_MSR(i));
> +               if ((maskm.lo & MTRR_PHYS_MASK_VALID) == 0)
> +                       return i;
> +       }
> +
> +       /* No free var mtrr */
> +       return -ENOSPC;
> +}
> +
> +int mtrr_set_next_var(uint type, uint64_t start, uint64_t size)
> +{
> +       int mtrr;
> +
> +       mtrr = get_free_var_mtrr();
> +       if (mtrr < 0)
> +               return mtrr;
> +
> +       set_var_mtrr(mtrr, MTRR_TYPE_WRPROT, start, size);

I think MTRR_TYPE_WRPROT should be parameter 'type'

> +       debug("MTRR %x: start=%x, size=%x\n", mtrr, (uint)start, (uint)size);
> +
> +       return 0;
> +}
> diff --git a/arch/x86/include/asm/mtrr.h b/arch/x86/include/asm/mtrr.h
> index 6f29e75ce65..672617256e9 100644
> --- a/arch/x86/include/asm/mtrr.h
> +++ b/arch/x86/include/asm/mtrr.h
> @@ -117,6 +117,18 @@ int mtrr_add_request(int type, uint64_t start, uint64_t size);
>   */
>  int mtrr_commit(bool do_caches);
>
> +/**
> + * mtrr_set_next_var() - set up a variable MTRR
> + *
> + * This finds the first free variable MTRR and sets to the given area
> + *
> + * @type:      Requested type (MTRR_TYPE_)
> + * @start:     Start address
> + * @size:      Size
> + * @return 0 on success, -ENOSPC if there are no more MTRRs
> + */
> +int mtrr_set_next_var(uint type, uint64_t base, uint64_t size);
> +
>  #endif
>
>  #if ((CONFIG_XIP_ROM_SIZE & (CONFIG_XIP_ROM_SIZE - 1)) != 0)
> --

Other than above,

Reviewed-by: Bin Meng <bmeng.cn at gmail.com>