linux-kernel - Re: [PATCH 2/4] iommu/exynos: Check if SysMMU v7 has VM registers

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Message-ID: <23357d34-4570-1309-6b6e-46055bdb8160@linaro.org>
Date:   Sun, 3 Jul 2022 21:10:09 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Sam Protsenko <semen.protsenko@...aro.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Janghyuck Kim <janghyuck.kim@...sung.com>,
        Cho KyongHo <pullip.cho@...sung.com>,
        Daniel Mentz <danielmentz@...gle.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        iommu@...ts.linux-foundation.org, iommu@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] iommu/exynos: Check if SysMMU v7 has VM registers

On 02/07/2022 23:37, Sam Protsenko wrote:
> SysMMU v7 can have Virtual Machine registers, which implement multiple
> translation domains. The driver should know if it's true or not, as VM
> registers shouldn't be accessed if not present. Read corresponding
> capabilities register to obtain that info, and store it in driver data.
> 
> Signed-off-by: Sam Protsenko <semen.protsenko@...aro.org>
> ---
>  drivers/iommu/exynos-iommu.c | 42 ++++++++++++++++++++++++++++++------
>  1 file changed, 36 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/iommu/exynos-iommu.c b/drivers/iommu/exynos-iommu.c
> index 28f8c8d93aa3..df6ddbebbe2b 100644
> --- a/drivers/iommu/exynos-iommu.c
> +++ b/drivers/iommu/exynos-iommu.c
> @@ -135,6 +135,9 @@ static u32 lv2ent_offset(sysmmu_iova_t iova)
>  #define CFG_SYSSEL	(1 << 22) /* System MMU 3.2 only */
>  #define CFG_FLPDCACHE	(1 << 20) /* System MMU 3.2+ only */
>  
> +#define CAPA0_CAPA1_EXIST		BIT(11)
> +#define CAPA1_VCR_ENABLED		BIT(14)
> +
>  /* common registers */
>  #define REG_MMU_CTRL		0x000
>  #define REG_MMU_CFG		0x004
> @@ -171,6 +174,10 @@ static u32 lv2ent_offset(sysmmu_iova_t iova)
>  #define REG_V5_FAULT_AR_VA	0x070
>  #define REG_V5_FAULT_AW_VA	0x080
>  
> +/* v7.x registers */
> +#define REG_V7_CAPA0		0x870
> +#define REG_V7_CAPA1		0x874
> +
>  #define has_sysmmu(dev)		(dev_iommu_priv_get(dev) != NULL)
>  
>  static struct device *dma_dev;
> @@ -274,6 +281,9 @@ struct sysmmu_drvdata {
>  	unsigned int version;		/* our version */
>  
>  	struct iommu_device iommu;	/* IOMMU core handle */
> +
> +	/* v7 fields */
> +	bool has_vcr;			/* virtual machine control register */
>  };
>  
>  static struct exynos_iommu_domain *to_exynos_domain(struct iommu_domain *dom)
> @@ -364,11 +374,7 @@ static void __sysmmu_disable_clocks(struct sysmmu_drvdata *data)
>  
>  static void __sysmmu_get_version(struct sysmmu_drvdata *data)
>  {
> -	u32 ver;
> -
> -	__sysmmu_enable_clocks(data);
> -
> -	ver = readl(data->sfrbase + REG_MMU_VERSION);
> +	const u32 ver = readl(data->sfrbase + REG_MMU_VERSION);


No need for const for local, non-pointer variables. There is no benefit
in preventing the modification and it is not a constant.

>  
>  	/* controllers on some SoCs don't report proper version */
>  	if (ver == 0x80000001u)
> @@ -378,6 +384,29 @@ static void __sysmmu_get_version(struct sysmmu_drvdata *data)
>  
>  	dev_dbg(data->sysmmu, "hardware version: %d.%d\n",
>  		MMU_MAJ_VER(data->version), MMU_MIN_VER(data->version));
> +}
> +
> +static bool __sysmmu_has_capa1(struct sysmmu_drvdata *data)
> +{
> +	const u32 capa0 = readl(data->sfrbase + REG_V7_CAPA0);

Same here and further.


Best regards,
Krzysztof