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

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Message-ID: <CAPLW+4=A7wTwH8a40hzDxn=4yT+jeMn2DX2WRyzxaX59hgbDnw@mail.gmail.com>
Date:   Fri, 8 Jul 2022 16:34:55 +0300
From:   Sam Protsenko <semen.protsenko@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        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 Sun, 3 Jul 2022 at 22:10, Krzysztof Kozlowski
<krzysztof.kozlowski@...aro.org> wrote:
>
> 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.
>

I'd say it's more a matter of taste, having "const" kinda disciplines
one. But I don't mind removing those bits, will do in v2.

> >
> >       /* 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