Re: [PATCH v3 2/6] misc: sram: add ability to mark sram sections as reserved

[Rob Herring <robherring2-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On Fri, Jul 5, 2013 at 7:41 AM, Heiko Stübner <heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org> wrote:
> Some SoCs need parts of their sram for special purposes. So while being part
> of the periphal, it should not be part of the genpool controlling the sram.

s/periphal/peripheral/

>
> Threfore add an option mmio-sram-reserved to keep arbitary portions of the

s/Threfore/Therefore/
s/arbitary/arbitrary/

> sram from being part of the pool.
>
> Suggested-by: Rob Herring <robherring2-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> Signed-off-by: Heiko Stuebner <heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org>
> Tested-by: Ulrich Prinz <ulrich.prinz-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org>
> ---
>  Documentation/devicetree/bindings/misc/sram.txt |    8 +++
>  drivers/misc/sram.c                             |   80 +++++++++++++++++++++--
>  2 files changed, 82 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/misc/sram.txt b/Documentation/devicetree/bindings/misc/sram.txt
> index 4d0a00e..eae080e 100644
> --- a/Documentation/devicetree/bindings/misc/sram.txt
> +++ b/Documentation/devicetree/bindings/misc/sram.txt
> @@ -8,9 +8,17 @@ Required properties:
>
>  - reg : SRAM iomem address range
>
> +Optional properties:
> +
> +- mmio-sram-reserved: ordered list of reserved chunks inside the sram that
> +  should not become part of the genalloc pool.

genalloc is linux specific. "should not be used by the OS" would be better.

> +  Format is <base size>, <base size>, ...; with base being relative to the
> +  reg property base.
> +
>  Example:
>
>  sram: sram@5c000000 {
>         compatible = "mmio-sram";
>         reg = <0x5c000000 0x40000>; /* 256 KiB SRAM at address 0x5c000000 */
> +       mmio-sram-reserved = <0x0 0x100>; /* reserve 0x5c000000-0x5c000100 */
>  };
> diff --git a/drivers/misc/sram.c b/drivers/misc/sram.c
> index afe66571..9131e4a 100644
> --- a/drivers/misc/sram.c
> +++ b/drivers/misc/sram.c
> @@ -42,6 +42,13 @@ static int sram_probe(struct platform_device *pdev)
>         struct sram_dev *sram;
>         struct resource *res;
>         unsigned long size;
> +       const __be32 *reserved_list = NULL;
> +       int reserved_size = 0;
> +       unsigned int cur_start = 0;
> +       unsigned int cur_size;
> +       unsigned int rstart;
> +       unsigned int rsize;

Use one line for each type.

> +       int i;
>         int ret;
>
>         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> @@ -65,12 +72,73 @@ static int sram_probe(struct platform_device *pdev)
>         if (!sram->pool)
>                 return -ENOMEM;
>
> -       ret = gen_pool_add_virt(sram->pool, (unsigned long)virt_base,
> -                               res->start, size, -1);
> -       if (ret < 0) {
> -               if (sram->clk)
> -                       clk_disable_unprepare(sram->clk);
> -               return ret;
> +       if (pdev->dev.of_node) {
> +               reserved_list = of_get_property(pdev->dev.of_node,
> +                                               "mmio-sram-reserved",
> +                                               &reserved_size);
> +               if (reserved_list) {
> +                       reserved_size /= sizeof(*reserved_list);
> +                       if (!reserved_size || reserved_size % 2) {
> +                               dev_warn(&pdev->dev, "wrong number of arguments in mmio-sram-reserved\n");
> +                               reserved_list = NULL;
> +                       }
> +               }
> +       }
> +
> +       if (!reserved_list)
> +               reserved_size = 0;

This can be moved to where you set reserved_list to NULL.

> +
> +       for (i = 0; i < (reserved_size + 2); i += 2) {
> +               if (i < reserved_size) {

This loop is hard to follow. For example, it is not immediate obvious
why you loop an extra time. I think it would be more straight forward
to determine the free regions first and then do the allocations. This
will require a kmalloc or fixed max number of regions, but would
improve readability.

Rob

> +                       /* get the next reserved block */
> +                       rstart = be32_to_cpu(*reserved_list++);
> +                       rsize = be32_to_cpu(*reserved_list++);
> +
> +                       /* catch unsorted list entries */
> +                       if (rstart < cur_start) {
> +                               dev_err(&pdev->dev,
> +                                       "unsorted reserved list (0x%x before current 0x%x)\n",
> +                                       rstart, cur_start);
> +                               if (sram->clk)
> +                                       clk_disable_unprepare(sram->clk);
> +                               return -EINVAL;
> +                       }
> +
> +                       dev_dbg(&pdev->dev,
> +                               "found reserved block 0x%x-0x%x\n",
> +                               rstart, rstart + rsize);
> +               } else {
> +                       /* the last chunk extends to the end of the region */
> +                       rstart = size;
> +                       rsize = 0;
> +               }
> +
> +               /* current start is in a reserved block */
> +               if (rstart <= cur_start) {
> +                       cur_start = rstart + rsize;
> +                       continue;
> +               }
> +
> +               /*
> +                * allocate the space between the current starting
> +                * address and the following reserved block, or the
> +                * end of the region.
> +                */
> +               cur_size = rstart - cur_start;
> +
> +               dev_dbg(&pdev->dev, "adding chunk 0x%x-0x%x\n",
> +                       cur_start, cur_start + cur_size);
> +               ret = gen_pool_add_virt(sram->pool,
> +                               (unsigned long)virt_base + cur_start,
> +                               res->start + cur_start, cur_size, -1);
> +               if (ret < 0) {
> +                       if (sram->clk)
> +                               clk_disable_unprepare(sram->clk);
> +                       return ret;
> +               }
> +
> +               /* next allocation after this reserved block */
> +               cur_start = rstart + rsize;
>         }
>
>         platform_set_drvdata(pdev, sram);
> --
> 1.7.10.4
>