linux-kernel - Re: [PATCH 1/5] iommu/io-pgtable-arm: Add BROKEN_NS quirk to disable shareability on ARM LPAE

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Date:   Wed, 9 Sep 2020 13:23:28 +0100
From:   Steven Price <steven.price@....com>
To:     Neil Armstrong <narmstrong@...libre.com>, robh@...nel.org,
        tomeu.vizoso@...labora.com, alyssa.rosenzweig@...labora.com
Cc:     dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-amlogic@...ts.infradead.org
Subject: Re: [PATCH 1/5] iommu/io-pgtable-arm: Add BROKEN_NS quirk to disable
 shareability on ARM LPAE

Subject: s/BROKEN_NS/BROKEN_SH/

Steve

On 08/09/2020 16:18, Neil Armstrong wrote:
> The coherency integration of the IOMMU in the Mali-G52 found in the Amlogic G12B SoCs
> is broken and leads to constant and random faults from the IOMMU.
> 
> Disabling shareability completely fixes the issue.
> 
> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
> ---
>   drivers/iommu/io-pgtable-arm.c | 7 ++++---
>   include/linux/io-pgtable.h     | 4 ++++
>   2 files changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
> index dc7bcf858b6d..d2d48dc86556 100644
> --- a/drivers/iommu/io-pgtable-arm.c
> +++ b/drivers/iommu/io-pgtable-arm.c
> @@ -440,7 +440,9 @@ static arm_lpae_iopte arm_lpae_prot_to_pte(struct arm_lpae_io_pgtable *data,
>   				<< ARM_LPAE_PTE_ATTRINDX_SHIFT);
>   	}
>   
> -	if (prot & IOMMU_CACHE)
> +	if (data->iop.cfg.quirks & IO_PGTABLE_QUIRK_ARM_BROKEN_SH)
> +		pte |= ARM_LPAE_PTE_SH_NS;
> +	else if (prot & IOMMU_CACHE)
>   		pte |= ARM_LPAE_PTE_SH_IS;
>   	else
>   		pte |= ARM_LPAE_PTE_SH_OS;
> @@ -1005,8 +1007,7 @@ arm_mali_lpae_alloc_pgtable(struct io_pgtable_cfg *cfg, void *cookie)
>   {
>   	struct arm_lpae_io_pgtable *data;
>   
> -	/* No quirks for Mali (hopefully) */
> -	if (cfg->quirks)
> +	if (cfg->quirks & ~(IO_PGTABLE_QUIRK_ARM_BROKEN_SH))
>   		return NULL;
>   
>   	if (cfg->ias > 48 || cfg->oas > 40)
> diff --git a/include/linux/io-pgtable.h b/include/linux/io-pgtable.h
> index 23285ba645db..efb9c8f20909 100644
> --- a/include/linux/io-pgtable.h
> +++ b/include/linux/io-pgtable.h
> @@ -86,6 +86,9 @@ struct io_pgtable_cfg {
>   	 *
>   	 * IO_PGTABLE_QUIRK_ARM_TTBR1: (ARM LPAE format) Configure the table
>   	 *	for use in the upper half of a split address space.
> +	 *
> +	 * IO_PGTABLE_QUIRK_ARM_BROKEN_SH: (ARM LPAE format) Disables shareability
> +	 *	when coherency integration is broken.
>   	 */
>   	#define IO_PGTABLE_QUIRK_ARM_NS		BIT(0)
>   	#define IO_PGTABLE_QUIRK_NO_PERMS	BIT(1)
> @@ -93,6 +96,7 @@ struct io_pgtable_cfg {
>   	#define IO_PGTABLE_QUIRK_ARM_MTK_EXT	BIT(3)
>   	#define IO_PGTABLE_QUIRK_NON_STRICT	BIT(4)
>   	#define IO_PGTABLE_QUIRK_ARM_TTBR1	BIT(5)
> +	#define IO_PGTABLE_QUIRK_ARM_BROKEN_SH	BIT(6)
>   	unsigned long			quirks;
>   	unsigned long			pgsize_bitmap;
>   	unsigned int			ias;
>