linux-kernel - Re: [PATCH 5/9] [media] s5p-jpeg: Add IOMMU support

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Date:   Fri, 2 Jun 2017 18:46:31 -0600
From:   Shuah Khan <shuahkhan@...il.com>
To:     Thierry Escande <thierry.escande@...labora.com>
Cc:     Andrzej Pietrasiewicz <andrzej.p@...sung.com>,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        shuahkh@....samsung.com
Subject: Re: [PATCH 5/9] [media] s5p-jpeg: Add IOMMU support

On Fri, Jun 2, 2017 at 10:02 AM, Thierry Escande
<thierry.escande@...labora.com> wrote:
> From: Tony K Nadackal <tony.kn@...sung.com>
>
> This patch adds support for IOMMU s5p-jpeg driver if the Exynos IOMMU
> and ARM DMA IOMMU configurations are supported. The address space is
> created with size limited to 256M and base address set to 0x20000000.
>
> Signed-off-by: Tony K Nadackal <tony.kn@...sung.com>
> Signed-off-by: Thierry Escande <thierry.escande@...labora.com>
> ---
>  drivers/media/platform/s5p-jpeg/jpeg-core.c | 77 +++++++++++++++++++++++++++++
>  1 file changed, 77 insertions(+)
>
> diff --git a/drivers/media/platform/s5p-jpeg/jpeg-core.c b/drivers/media/platform/s5p-jpeg/jpeg-core.c
> index 770a709..5569b99 100644
> --- a/drivers/media/platform/s5p-jpeg/jpeg-core.c
> +++ b/drivers/media/platform/s5p-jpeg/jpeg-core.c
> @@ -28,6 +28,14 @@
>  #include <media/v4l2-ioctl.h>
>  #include <media/videobuf2-v4l2.h>
>  #include <media/videobuf2-dma-contig.h>
> +#if defined(CONFIG_EXYNOS_IOMMU) && defined(CONFIG_ARM_DMA_USE_IOMMU)
> +#include <asm/dma-iommu.h>
> +#include <linux/dma-iommu.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/iommu.h>
> +#include <linux/kref.h>
> +#include <linux/of_platform.h>
> +#endif
>
>  #include "jpeg-core.h"
>  #include "jpeg-hw-s5p.h"
> @@ -35,6 +43,10 @@
>  #include "jpeg-hw-exynos3250.h"
>  #include "jpeg-regs.h"
>
> +#if defined(CONFIG_EXYNOS_IOMMU) && defined(CONFIG_ARM_DMA_USE_IOMMU)
> +static struct dma_iommu_mapping *mapping;
> +#endif
> +
>  static struct s5p_jpeg_fmt sjpeg_formats[] = {
>         {
>                 .name           = "JPEG JFIF",
> @@ -956,6 +968,60 @@ static void exynos4_jpeg_parse_q_tbl(struct s5p_jpeg_ctx *ctx)
>         }
>  }
>
> +#if defined(CONFIG_EXYNOS_IOMMU) && defined(CONFIG_ARM_DMA_USE_IOMMU)
> +static int jpeg_iommu_init(struct platform_device *pdev)
> +{
> +       struct device *dev = &pdev->dev;
> +       int err;
> +
> +       mapping = arm_iommu_create_mapping(&platform_bus_type, 0x20000000,
> +                                          SZ_512M);

Change log says 256M??

What happens when another driver uses the same start point?
exynos drm uses the same  looks like

EXYNOS_DEV_ADDR_START   0x20000000

> +       if (IS_ERR(mapping)) {
> +               dev_err(dev, "IOMMU mapping failed\n");
> +               return PTR_ERR(mapping);
> +       }
> +
> +       dev->dma_parms = devm_kzalloc(dev, sizeof(*dev->dma_parms), GFP_KERNEL);
> +       if (!dev->dma_parms) {
> +               err = -ENOMEM;
> +               goto error_alloc;
> +       }
> +
> +       err = dma_set_max_seg_size(dev, 0xffffffffu);

You could use DMA_BIT_MASK(32) instead of 0xffffffffu

> +       if (err)
> +               goto error;
> +
> +       err = arm_iommu_attach_device(dev, mapping);
> +       if (err)
> +               goto error;
> +
> +       return 0;
> +
> +error:
> +       devm_kfree(dev, dev->dma_parms);
> +       dev->dma_parms = NULL;
> +
> +error_alloc:
> +       arm_iommu_release_mapping(mapping);
> +       mapping = NULL;
> +
> +       return err;
> +}
> +
> +static void jpeg_iommu_deinit(struct platform_device *pdev)
> +{
> +       struct device *dev = &pdev->dev;
> +
> +       if (mapping) {
> +               arm_iommu_detach_device(dev);
> +               devm_kfree(dev, dev->dma_parms);
> +               dev->dma_parms = NULL;
> +               arm_iommu_release_mapping(mapping);
> +               mapping = NULL;
> +       }
> +}
> +#endif
> +
>  /*
>   * ============================================================================
>   * Device file operations
> @@ -2816,6 +2882,13 @@ static int s5p_jpeg_probe(struct platform_device *pdev)
>         spin_lock_init(&jpeg->slock);
>         jpeg->dev = &pdev->dev;
>
> +#if defined(CONFIG_EXYNOS_IOMMU) && defined(CONFIG_ARM_DMA_USE_IOMMU)
> +       ret = jpeg_iommu_init(pdev);
> +       if (ret) {
> +               dev_err(&pdev->dev, "IOMMU Initialization failed\n");
> +               return ret;
> +       }
> +#endif

You might be able to avoid use of ifdefs if you define stubs for !defines case.

>         /* memory-mapped registers */
>         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>
> @@ -2962,6 +3035,10 @@ static int s5p_jpeg_remove(struct platform_device *pdev)
>                         clk_disable_unprepare(jpeg->clocks[i]);
>         }
>
> +#if defined(CONFIG_EXYNOS_IOMMU) && defined(CONFIG_ARM_DMA_USE_IOMMU)
> +       jpeg_iommu_deinit(pdev);
> +#endif
> +
>         return 0;
>  }
>
> --
> 2.7.4
>