Re: [PATCH] IOMMU: arm-smmu-v3: Use STE.S1STALLD only when supported

[Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>]

Hi Prem,

Thanks for the patch. Just a few minor comments...

On Mon, Nov 16, 2015 at 02:18:20PM +0530, pmallapp-dY08KVG/lbpWk0Htik3J/w@public.gmane.org wrote:
> From: Prem Mallappa <pmallapp-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
> 
> Also fix the STALLD check.

Can you extend the commit message please to explain that it is ILLEGAL
to set STE.S1STALLD to 1 if stage 1 is enabled and either the stall or
terminate models are not supported?

> Signed-off-by: Prem Mallappa <pmallapp-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
> ---
>  drivers/iommu/arm-smmu-v3.c | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> index ed409cb..804671c 100644
> --- a/drivers/iommu/arm-smmu-v3.c
> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -38,7 +38,9 @@
>  #define IDR0_ST_LVL_SHIFT		27
>  #define IDR0_ST_LVL_MASK		0x3
>  #define IDR0_ST_LVL_2LVL		(1 << IDR0_ST_LVL_SHIFT)
> -#define IDR0_STALL_MODEL		(3 << 24)
> +#define IDR0_STALL_SHIFT		24

To keep the style consistent, can you also add IDR0_STALL_MASK please...

> +#define IDR0_STALL_MODEL_STALL		0x0
> +#define IDR0_STALL_MODEL_FORCE		0x2

... and shift these guys left by IDR0_STALL_SHIFT?

>
>  #define IDR0_TTENDIAN_SHIFT		21
>  #define IDR0_TTENDIAN_MASK		0x3
>  #define IDR0_TTENDIAN_LE		(2 << IDR0_TTENDIAN_SHIFT)
> @@ -1051,12 +1053,14 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_device *smmu, u32 sid,
>  			 STRTAB_STE_1_S1C_CACHE_WBRA
>  			 << STRTAB_STE_1_S1COR_SHIFT |
>  			 STRTAB_STE_1_S1C_SH_ISH << STRTAB_STE_1_S1CSH_SHIFT |
> -			 STRTAB_STE_1_S1STALLD |
>  #ifdef CONFIG_PCI_ATS
>  			 STRTAB_STE_1_EATS_TRANS << STRTAB_STE_1_EATS_SHIFT |
>  #endif
>  			 STRTAB_STE_1_STRW_NSEL1 << STRTAB_STE_1_STRW_SHIFT);
>  
> +		if (smmu->features & ARM_SMMU_FEAT_STALLS)
> +			dst[1] |= cpu_to_le64(STRTAB_STE_1_S1STALLD);
> +
>  		val |= (ste->s1_cfg->cdptr_dma & STRTAB_STE_0_S1CTXPTR_MASK
>  		        << STRTAB_STE_0_S1CTXPTR_SHIFT) |
>  			STRTAB_STE_0_CFG_S1_TRANS;
> @@ -2483,8 +2487,14 @@ static int arm_smmu_device_probe(struct arm_smmu_device *smmu)
>  		dev_warn(smmu->dev, "IDR0.COHACC overridden by dma-coherent property (%s)\n",
>  			 coherent ? "true" : "false");
>  
> -	if (reg & IDR0_STALL_MODEL)
> +	switch ((reg >> IDR0_STALL_SHIFT) & 0x3) {

Then structure this more like the TTENDIAN code:

  switch (reg & IDR0_STALL_MASK << IDR0_STALL_SHIFT) {

> +	case IDR0_STALL_MODEL_STALL:
> +	case IDR0_STALL_MODEL_FORCE:
>  		smmu->features |= ARM_SMMU_FEAT_STALLS;
> +		break;
> +	default:
> +		break;
> +	}

I think you can drop the default case, or does GCC complain?

Will