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Message-ID: <5356831F.40006@ti.com>
Date: Tue, 22 Apr 2014 17:56:31 +0300
From: Grygorii Strashko <grygorii.strashko@...com>
To: Rob Herring <robherring2@...il.com>,
Santosh Shilimkar <santosh.shilimkar@...com>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Russell King <linux@....linux.org.uk>,
Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
Grant Likely <grant.likely@...aro.org>,
Rob Herring <robh+dt@...nel.org>,
Catalin Marinas <catalin.marinas@....com>,
Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v2 2/7] of: introduce of_dma_get_range() helper
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@...com> wrote:
>> From: Grygorii Strashko <grygorii.strashko@...com>
>>
>> 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@...uxfoundation.org>
>> Cc: Russell King <linux@....linux.org.uk>
>> Cc: Arnd Bergmann <arnd@...db.de>
>> Cc: Olof Johansson <olof@...om.net>
>> Cc: Grant Likely <grant.likely@...aro.org>
>> Cc: Rob Herring <robh+dt@...nel.org>
>> Cc: Catalin Marinas <catalin.marinas@....com>
>> Cc: Linus Walleij <linus.walleij@...aro.org>
>> Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
>> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@...com>
>> ---
>> 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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