[Skiboot] [PATCH] phb4: Enable PHB MMIO-0/1 Bars only when mmio window exists

[Oliver]

On Tue, Aug 21, 2018 at 8:44 PM, Vaibhav Jain <vaibhav at linux.ibm.com> wrote:
> Presently phb4_probe_stack() will always enable PHB MMIO0/1 windows
> even if they doesn't exist in phy_map. Hence we do some minor shuffling
> in the phb4_probe_stack() so that MMIO-0/1 Bars are only enabled if
> there corresponding MMIO window exists in the phy_map.

In what circumstances do we have PHBs that aren't in the phys map?

> Signed-off-by: Vaibhav Jain <vaibhav at linux.ibm.com>
> ---
>  hw/phb4.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/hw/phb4.c b/hw/phb4.c
> index d1245dce..935b0e92 100644
> --- a/hw/phb4.c
> +++ b/hw/phb4.c
> @@ -5580,25 +5580,28 @@ static void phb4_probe_stack(struct dt_node *stk_node, uint32_t pec_index,
>         /* Same with MMIO windows */
>         phys_map_get(gcid, PHB4_64BIT_MMIO, phb_num, &mmio0_bar, &mmio0_sz);
>         mmio0_bmask =  (~(mmio0_sz - 1)) & 0x00FFFFFFFFFFFFFFULL;
> -       xscom_write(gcid, nest_stack + XPEC_NEST_STK_MMIO_BAR0, mmio0_bar << 8);
> -       xscom_write(gcid, nest_stack + XPEC_NEST_STK_MMIO_BAR0_MASK, mmio0_bmask << 8);
>
>         phys_map_get(gcid, PHB4_32BIT_MMIO, phb_num, &mmio1_bar, &mmio1_sz);
>         mmio1_bmask =  (~(mmio1_sz - 1)) & 0x00FFFFFFFFFFFFFFULL;
> -       xscom_write(gcid, nest_stack + XPEC_NEST_STK_MMIO_BAR1, mmio1_bar << 8);
> -       xscom_write(gcid, nest_stack + XPEC_NEST_STK_MMIO_BAR1_MASK, mmio1_bmask << 8);


> -       bar_en |= XPEC_NEST_STK_BAR_EN_MMIO0 | XPEC_NEST_STK_BAR_EN_MMIO1;

I think you can remove just this line and drop the rest of the changes
in the patch. I'd rather we kept the XSCOM writes here so that we know
the BAR and MASK registers are explicitly set to zero even when the
BAR is disabled.

>         /* Build MMIO windows list */
>         mmio_win_sz = 0;
>         if (mmio0_bar) {
>                 mmio_win[mmio_win_sz++] = mmio0_bar;
>                 mmio_win[mmio_win_sz++] = mmio0_sz;
> +               xscom_write(gcid, nest_stack + XPEC_NEST_STK_MMIO_BAR0,
> +                           mmio0_bar << 8);
> +               xscom_write(gcid, nest_stack + XPEC_NEST_STK_MMIO_BAR0_MASK,
> +                           mmio0_bmask << 8);
>                 bar_en |= XPEC_NEST_STK_BAR_EN_MMIO0;
>         }
>         if (mmio1_bar) {
>                 mmio_win[mmio_win_sz++] = mmio1_bar;
>                 mmio_win[mmio_win_sz++] = mmio1_sz;
> +               xscom_write(gcid, nest_stack + XPEC_NEST_STK_MMIO_BAR1,
> +                           mmio1_bar << 8);
> +               xscom_write(gcid, nest_stack + XPEC_NEST_STK_MMIO_BAR1_MASK,
> +                           mmio1_bmask << 8);
>                 bar_en |= XPEC_NEST_STK_BAR_EN_MMIO1;
>         }
>
> --
> 2.17.1
>
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