linux-kernel - Re: [PATCH v9 4/6] iommu/arm-smmu-v3: Add CS_NONE quirk for CONFIG_TEGRA241

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Message-ID: <20240702174307.GB4740@willie-the-truck>
Date: Tue, 2 Jul 2024 18:43:07 +0100
From: Will Deacon <will@...nel.org>
To: Nicolin Chen <nicolinc@...dia.com>
Cc: robin.murphy@....com, joro@...tes.org, jgg@...dia.com,
	thierry.reding@...il.com, vdumpa@...dia.com, jonathanh@...dia.com,
	linux-kernel@...r.kernel.org, iommu@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, linux-tegra@...r.kernel.org
Subject: Re: [PATCH v9 4/6] iommu/arm-smmu-v3: Add CS_NONE quirk for
 CONFIG_TEGRA241_CMDQV

On Wed, Jun 12, 2024 at 02:45:31PM -0700, Nicolin Chen wrote:
> The CMDQV extension in NVIDIA Tegra241 SoC only supports CS_NONE in the
> CS field of CMD_SYNC. Add a quirk flag to accommodate that.
> 
> Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
> Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
> ---
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 8 +++++++-
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 3 +++
>  2 files changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> index c864c634cd23..ba0e24d5ffbf 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -345,6 +345,11 @@ static void arm_smmu_cmdq_build_sync_cmd(u64 *cmd, struct arm_smmu_device *smmu,
>  		 FIELD_PREP(CMDQ_SYNC_0_MSH, ARM_SMMU_SH_ISH) |
>  		 FIELD_PREP(CMDQ_SYNC_0_MSIATTR, ARM_SMMU_MEMATTR_OIWB);
>  
> +	if (q->quirks & CMDQ_QUIRK_SYNC_CS_NONE_ONLY) {
> +		cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_CS, CMDQ_SYNC_0_CS_NONE);
> +		return;
> +	}
> +
>  	if (!(smmu->options & ARM_SMMU_OPT_MSIPOLL)) {
>  		cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_CS, CMDQ_SYNC_0_CS_SEV);
>  		return;
> @@ -690,7 +695,8 @@ static int arm_smmu_cmdq_poll_until_sync(struct arm_smmu_device *smmu,
>  					 struct arm_smmu_cmdq *cmdq,
>  					 struct arm_smmu_ll_queue *llq)
>  {
> -	if (smmu->options & ARM_SMMU_OPT_MSIPOLL)
> +	if (smmu->options & ARM_SMMU_OPT_MSIPOLL &&
> +	    !(cmdq->q.quirks & CMDQ_QUIRK_SYNC_CS_NONE_ONLY))
>  		return __arm_smmu_cmdq_poll_until_msi(smmu, cmdq, llq);
>  
>  	return __arm_smmu_cmdq_poll_until_consumed(smmu, cmdq, llq);
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> index 180c0b1e0658..01227c0de290 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> @@ -543,6 +543,9 @@ struct arm_smmu_queue {
>  
>  	u32 __iomem			*prod_reg;
>  	u32 __iomem			*cons_reg;
> +
> +#define CMDQ_QUIRK_SYNC_CS_NONE_ONLY	BIT(0)	/* CMD_SYNC CS field supports CS_NONE only */
> +	u32				quirks;

Please can you use the existing smmu->options field instead of adding
another place to track quirks? Or do you need this only for some of the
queues for a given SMMU device?

Thanks,

Will