Re: [PATCH v8 07/21] iommu/io-pgtable-arm-v7s: Extend MediaTek 4GB Mode

Will Deacon
2019-07-10T14:37:04Z

On Sat, Jun 29, 2019 at 10:09:13AM +0800, Yong Wu wrote:
> MediaTek extend the arm v7s descriptor to support the dram over 4GB.
>
> In the mt2712 and mt8173, it's called "4GB mode", the physical address
> is from 0x4000_0000 to 0x1_3fff_ffff, but from EMI point of view, it
> is remapped to high address from 0x1_0000_0000 to 0x1_ffff_ffff, the
> bit32 is always enabled. thus, in the M4U, we always enable the bit9
> for all PTEs which means to enable bit32 of physical address.
>
> but in mt8183, M4U support the dram from 0x4000_0000 to 0x3_ffff_ffff
> which isn't remaped. We extend the PTEs: the bit9 represent bit32 of
> PA and the bit4 represent bit33 of PA. Meanwhile the iova still is
> 32bits.

What happens if bit4 is set in the pte for mt2712 or mt8173? Perhaps the
io-pgtable backend should be allowing oas > 32 when
IO_PGTABLE_QUIRK_ARM_MTK_4GB is set, and then enforcing that itself.

> In order to unify code, in the "4GB mode", we add the bit32 for the
> physical address manually in our driver.
>
> Correspondingly, Adding bit32 and bit33 for the PA in the iova_to_phys
> has to been moved into v7s.
>
> Regarding whether the pagetable address could be over 4GB, the mt8183
> support it while the previous mt8173 don't. thus keep it as is.
>
> Signed-off-by: Yong Wu <yong.wu@mediatek.com>
> Reviewed-by: Robin Murphy <robin.murphy@arm.com>
> Reviewed-by: Evan Green <evgreen@chromium.org>
> ---
> Comparing with the previous one:
> 1). Add a new patch "iommu/mediatek: Fix iova_to_phys PA start for 4GB
> mode" before this one. Thus rebase it.
> A little difference: in the 4gb mode, we add bit32 for PA. and the PA got
> from iova_to_phys always have bit32 here, thus we should adjust it to locate
> the valid pa.
> 2). Add this code suggested from Evan.
> if (!data->plat_data->has_4gb_mode)
> data->enable_4GB = false;
> ---
> drivers/iommu/io-pgtable-arm-v7s.c | 31 ++++++++++++++++++++++++-------
> drivers/iommu/mtk_iommu.c | 29 ++++++++++++++++++-----------
> drivers/iommu/mtk_iommu.h | 1 +
> 3 files changed, 43 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/iommu/io-pgtable-arm-v7s.c b/drivers/iommu/io-pgtable-arm-v7s.c
> index 94c38db..4077822 100644
> --- a/drivers/iommu/io-pgtable-arm-v7s.c
> +++ b/drivers/iommu/io-pgtable-arm-v7s.c
> @@ -123,7 +123,9 @@
> #define ARM_V7S_TEX_MASK 0x7
> #define ARM_V7S_ATTR_TEX(val) (((val) & ARM_V7S_TEX_MASK) << ARM_V7S_TEX_SHIFT)
>
> -#define ARM_V7S_ATTR_MTK_4GB BIT(9) /* MTK extend it for 4GB mode */
> +/* MediaTek extend the two bits below for over 4GB mode */
> +#define ARM_V7S_ATTR_MTK_PA_BIT32 BIT(9)
> +#define ARM_V7S_ATTR_MTK_PA_BIT33 BIT(4)
>
> /* *well, except for TEX on level 2 large pages, of course :( */
> #define ARM_V7S_CONT_PAGE_TEX_SHIFT 6
> @@ -190,13 +192,22 @@ static dma_addr_t __arm_v7s_dma_addr(void *pages)
> static arm_v7s_iopte paddr_to_iopte(phys_addr_t paddr, int lvl,
> struct io_pgtable_cfg *cfg)
> {
> - return paddr & ARM_V7S_LVL_MASK(lvl);
> + arm_v7s_iopte pte = paddr & ARM_V7S_LVL_MASK(lvl);
> +
> + if (cfg->quirks & IO_PGTABLE_QUIRK_ARM_MTK_4GB) {
> + if (paddr & BIT_ULL(32))
> + pte |= ARM_V7S_ATTR_MTK_PA_BIT32;
> + if (paddr & BIT_ULL(33))
> + pte |= ARM_V7S_ATTR_MTK_PA_BIT33;
> + }
> + return pte;
> }
>
> static phys_addr_t iopte_to_paddr(arm_v7s_iopte pte, int lvl,
> struct io_pgtable_cfg *cfg)
> {
> arm_v7s_iopte mask;
> + phys_addr_t paddr;
>
> if (ARM_V7S_PTE_IS_TABLE(pte, lvl))
> mask = ARM_V7S_TABLE_MASK;
> @@ -205,7 +216,14 @@ static phys_addr_t iopte_to_paddr(arm_v7s_iopte pte, int lvl,
> else
> mask = ARM_V7S_LVL_MASK(lvl);
>
> - return pte & mask;
> + paddr = pte & mask;
> + if (cfg->quirks & IO_PGTABLE_QUIRK_ARM_MTK_4GB) {
> + if (pte & ARM_V7S_ATTR_MTK_PA_BIT32)
> + paddr |= BIT_ULL(32);
> + if (pte & ARM_V7S_ATTR_MTK_PA_BIT33)
> + paddr |= BIT_ULL(33);
> + }
> + return paddr;

I think this relies on CONFIG_PHYS_ADDR_T_64BIT, which isn't always set on
32-bit ARM.

Will