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

From: [email-masked] (Grygorii Strashko)
Date: Tue, 22 Apr 2014 17:56:31 +0300

Hi Rob,

On 04/21/2014 06:29 PM, Rob Herring wrote:
> On Sat, Apr 19, 2014 at 9:32 AM, Santosh Shilimkar
> <[email-masked]> wrote:
>> From: Grygorii Strashko <[email-masked]>
>>
>> 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 <[email-masked]>
>> Cc: Russell King <[email-masked]>
>> Cc: Arnd Bergmann <[email-masked]>
>> Cc: Olof Johansson <[email-masked]>
>> Cc: Grant Likely <[email-masked]>
>> Cc: Rob Herring <[email-masked]>
>> Cc: Catalin Marinas <[email-masked]>
>> Cc: Linus Walleij <[email-masked]>
>> Signed-off-by: Grygorii Strashko <[email-masked]>
>> Signed-off-by: Santosh Shilimkar <[email-masked]>
>> ---
>>   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