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

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Message-ID: <20190710143649.w5dplhzdpi3bxp7e@willie-the-truck>
Date:   Wed, 10 Jul 2019 15:36:50 +0100
From:   Will Deacon <will@...nel.org>
To:     Yong Wu <yong.wu@...iatek.com>
Cc:     Joerg Roedel <joro@...tes.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Robin Murphy <robin.murphy@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Evan Green <evgreen@...omium.org>,
        Tomasz Figa <tfiga@...gle.com>,
        Will Deacon <will.deacon@....com>,
        linux-mediatek@...ts.infradead.org, srv_heupstream@...iatek.com,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, yingjoe.chen@...iatek.com,
        youlin.pei@...iatek.com, Nicolas Boichat <drinkcat@...omium.org>,
        anan.sun@...iatek.com, Matthias Kaehlcke <mka@...omium.org>
Subject: Re: [PATCH v8 07/21] iommu/io-pgtable-arm-v7s: Extend MediaTek 4GB
 Mode

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@...iatek.com>
> Reviewed-by: Robin Murphy <robin.murphy@....com>
> Reviewed-by: Evan Green <evgreen@...omium.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