Re: [PATCH v2 2/7] of: introduce of_dma_get_range() helper

[Grygorii Strashko]

Hi Rob,

On 04/21/2014 06:29 PM, Rob Herring wrote:
> On Sat, Apr 19, 2014 at 9:32 AM, Santosh Shilimkar
> <santosh.shilimkar@xxxxxx> wrote:
> > From: Grygorii Strashko <grygorii.strashko@xxxxxx>
> >
> > The of_dma_get_range() allows to find "dma-range" property for
> > the specified device and parse it.
> >   dma-ranges format:
> >     DMA addr (dma_addr)          : naddr cells
> >     CPU addr (phys_addr_t)       : pna cells
> >     size                         : nsize cells
> >
> > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
> > Cc: Arnd Bergmann <arnd@xxxxxxxx>
> > Cc: Olof Johansson <olof@xxxxxxxxx>
> > Cc: Grant Likely <grant.likely@xxxxxxxxxx>
> > Cc: Rob Herring <robh+dt@xxxxxxxxxx>
> > Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> > Cc: Linus Walleij <linus.walleij@xxxxxxxxxx>
> > Signed-off-by: Grygorii Strashko <grygorii.strashko@xxxxxx>
> > Signed-off-by: Santosh Shilimkar <santosh.shilimkar@xxxxxx>
> > ---
> >   drivers/of/platform.c       |   85 +++++++++++++++++++++++++++++++++++++++++++
> >   include/linux/of_platform.h |    8 ++++
>
> This belongs in drivers/of/address.c and of_address.h.
>
> >   2 files changed, 93 insertions(+)
> >
> > diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> > index 404d1da..2265a55 100644
> > --- a/drivers/of/platform.c
> > +++ b/drivers/of/platform.c
> > @@ -485,4 +485,89 @@ int of_platform_populate(struct device_node *root,
> >          return rc;
> >   }
> >   EXPORT_SYMBOL_GPL(of_platform_populate);
> > +
> > +/**
> > + * of_dma_get_range - Get DMA range info
> > + * @np:                device node to get DMA range info
> > + * @dma_addr:  pointer to store initial DMA address of DMA range
> > + * @paddr:     pointer to store initial CPU address of DMA range
> > + * @size:      pointer to store size of DMA range
> > + *
> > + * Look in bottom up direction for the first "dma-range" property
>
> dma-ranges
>
> > + * and parse it.
> > + *  dma-ranges format:
> > + *     DMA addr (dma_addr)     : naddr cells
> > + *     CPU addr (phys_addr_t)  : pna cells
> > + *     size                    : nsize cells
> > + *
> > + * It returns -ENODEV if "dma-ranges" property was not found
> > + * for this device in DT.
> > + */
> > +extern int of_dma_get_range(struct device_node *np, dma_addr_t *dma_addr,
>
> drop extern.
>
> > +               phys_addr_t *paddr, phys_addr_t *size)
> > +{
> > +       struct device_node *node = np;
> > +       const u32 *ranges = NULL;
>
> __be32
>
> > +       int len, naddr, nsize, pna;
> > +       int ret = 0;
> > +
> > +       if (!node)
> > +               return -EINVAL;
> > +
> > +       while (1) {
> > +               naddr = of_n_addr_cells(node);
> > +               nsize = of_n_size_cells(node);
> > +               node = of_get_next_parent(node);
> > +               if (!node)
> > +                       break;
> > +
> > +               ranges = of_get_property(node, "dma-ranges", &len);
> > +
> > +               /* Ignore empty ranges, they imply no translation required */
> > +               if (ranges && len > 0)
> > +                       break;
> > +
> > +               /*
> > +                * At least empty ranges has to be defined for parent node if
> > +                * DMA is supported
> > +                */
> > +               if (!ranges)
> > +                       break;
>
> You need an of_node_put here if you are getting the next parent.

Seems, It's not needed, because of_get_next_parent() does following:
	parent = of_node_get(node->parent);
	of_node_put(node);

> > +       }
> > +
> > +       if (!ranges) {
> > +               pr_debug("%s: no dma-ranges found for node(%s)\n",
> > +                        __func__, np->full_name);
> > +               ret = -ENODEV;
> > +               goto out;
> > +       }
> > +
> > +       len /= sizeof(u32);
> > +
> > +       pna = of_n_addr_cells(node);
> > +
> > +       /* dma-ranges format:
> > +        * DMA addr     : naddr cells
> > +        * CPU addr     : pna cells
> > +        * size         : nsize cells
> > +        */
> > +       *dma_addr = of_read_number(ranges, naddr);
>
> You should set this after the following call succeeds.
>
> > +       *paddr = of_translate_dma_address(np, ranges);
>
> This is going to search for dma-ranges again, but you have already
> done that. Is there a case that just reading the CPU addr will not
> work? I suppose we could have more than one level of translation. It
> also seems a bit abusive that the DMA address is the ranges property.
> I don't really have a better suggestion though.

I think, We need to keep using of_translate_dma_address(), because
this code intended to be generic and, as result, there is no
guarantee that we will always have one level of translations.

> > +       if (*paddr == OF_BAD_ADDR) {
>
> As I mentioned, this is potentially a size mismatch.

Thanks for your review.

Regards,
Grygorii

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