linux-kernel - Re: [PATCH v8 08/12] iommu/exynos: remove prefetch buffer setting when enabling System MMU

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Message-ID: <CANEJEGtWTZHZEr=XzPXHFbJtP7U5JFD-o58kRjLe23XaTzv=fA@mail.gmail.com>
Date:	Fri, 26 Jul 2013 10:35:59 -0700
From:	Grant Grundler <grundler@...omium.org>
To:	Cho KyongHo <pullip.cho@...sung.com>
Cc:	Linux ARM Kernel <linux-arm-kernel@...ts.infradead.org>,
	Linux IOMMU <iommu@...ts.linux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linux Samsung SOC <linux-samsung-soc@...r.kernel.org>,
	Hyunwoong Kim <khw0178.kim@...sung.com>,
	Joerg Roedel <joro@...tes.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Prathyush <prathyush.k@...sung.com>,
	Rahul Sharma <rahul.sharma@...sung.com>,
	Subash Patel <supash.ramaswamy@...aro.org>,
	Keyyoung Park <keyyoung.park@...sung.com>,
	Grant Grundler <grundler@...omium.org>,
	Antonios Motakis <a.motakis@...tualopensystems.com>,
	kvmarm@...ts.cs.columbia.edu,
	Sachin Kamat <sachin.kamat@...aro.org>
Subject: Re: [PATCH v8 08/12] iommu/exynos: remove prefetch buffer setting
 when enabling System MMU

On Fri, Jul 26, 2013 at 4:28 AM, Cho KyongHo <pullip.cho@...sung.com> wrote:
> Prefetch buffer must be handled accurately, exact range of a buffer,
> frame by frame manually. Otherwise, it may causes page fault or
> deadlock in System MMU.
> Thus this patch removes prefetch buffer setting when System MMU is
> initialized(enabled).
>
> Signed-off-by: Cho KyongHo <pullip.cho@...sung.com>

Reviewed-by: Grant Grundler <grundler@...omium.org>

BTW, cscope doesn't find any callers of exynos_sysmmu_enable().
Want to submit another patch to remove it?

(Note I'm talking about exynos_sysmmu_enable() without "__" prefix).

cheers,
grant

> ---
>  drivers/iommu/exynos-iommu.c |   32 +++++++++++++++++++++++++++-----
>  1 files changed, 27 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/iommu/exynos-iommu.c b/drivers/iommu/exynos-iommu.c
> index cfc02ed..87f6bb7 100644
> --- a/drivers/iommu/exynos-iommu.c
> +++ b/drivers/iommu/exynos-iommu.c
> @@ -80,6 +80,8 @@
>  #define CTRL_BLOCK     0x7
>  #define CTRL_DISABLE   0x0
>
> +#define CFG_FLPDCACHE  (1 << 20) /* System MMU 3.2+ only */
> +
>  #define REG_MMU_CTRL           0x000
>  #define REG_MMU_CFG            0x004
>  #define REG_MMU_STATUS         0x008
> @@ -96,6 +98,9 @@
>
>  #define REG_MMU_VERSION                0x034
>
> +#define MMU_MAJ_VER(reg)       (reg >> 28)
> +#define MMU_MIN_VER(reg)       ((reg >> 21) & 0x7F)
> +
>  #define REG_PB0_SADDR          0x04C
>  #define REG_PB0_EADDR          0x050
>  #define REG_PB1_SADDR          0x054
> @@ -200,6 +205,22 @@ static bool is_sysmmu_active(struct sysmmu_drvdata *data)
>         return data->activations > 0;
>  }
>
> +static unsigned int __sysmmu_version(struct sysmmu_drvdata *data,
> +                                    int idx, unsigned int *minor)
> +{
> +       unsigned long major;
> +
> +       major = readl(data->sfrbases[idx] + REG_MMU_VERSION);
> +
> +       if (minor)
> +               *minor = MMU_MIN_VER(major);
> +
> +       if (MMU_MAJ_VER(major) > 3)
> +               return 1;
> +
> +       return MMU_MAJ_VER(major);
> +}
> +
>  static void sysmmu_unblock(void __iomem *sfrbase)
>  {
>         __raw_writel(CTRL_ENABLE, sfrbase + REG_MMU_CTRL);
> @@ -460,14 +481,15 @@ static int __exynos_sysmmu_enable(struct sysmmu_drvdata *data,
>         data->pgtable = pgtable;
>
>         for (i = 0; i < data->nsfrs; i++) {
> +               unsigned int min;
> +
>                 __sysmmu_set_ptbase(data->sfrbases[i], pgtable);
>
> -               if ((readl(data->sfrbases[i] + REG_MMU_VERSION) >> 28) == 3) {
> -                       /* System MMU version is 3.x */
> -                       __raw_writel((1 << 12) | (2 << 28),
> +               if ((__sysmmu_version(data, i, &min) == 3) && (min > 1)) {
> +                       unsigned long cfg;
> +                       cfg = __raw_readl(data->sfrbases[i] + REG_MMU_CFG);
> +                       __raw_writel(cfg | CFG_FLPDCACHE,
>                                         data->sfrbases[i] + REG_MMU_CFG);
> -                       __sysmmu_set_prefbuf(data->sfrbases[i], 0, -1, 0);
> -                       __sysmmu_set_prefbuf(data->sfrbases[i], 0, -1, 1);
>                 }
>
>                 __raw_writel(CTRL_ENABLE, data->sfrbases[i] + REG_MMU_CTRL);
> --
> 1.7.2.5
>
>
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