Subject: [RFC PATCH 1/2] of: Add generic device tree DMA helpers

From: [email-masked] (Nicolas Ferre)
Date: Thu, 23 Feb 2012 16:51:56 +0100

On 02/23/2012 11:03 AM, Cousson, Benoit :
> Salut Nico,

Coucou Benoit ;-)

> On 2/22/2012 11:59 AM, Nicolas Ferre wrote:
>> On 01/27/2012 06:29 PM, Cousson, Benoit :
>>> Add some basic helpers to retrieve a DMA controller device_node
>>> and the DMA request line number.
>>>
>>> For legacy reason another API will export the DMA request number
>>> into a Linux resource of type IORESOURCE_DMA.
>>> This API is usable only on system with an unique DMA controller.
>>
>> Hi,
>>
>> I followed that discussion and I like very much the biding that Benoit
>> is proposing. It will help me a lot with my current work on Atmel DMA
>> controller.
>>
>> If I understand correctly, some rework is needed before it can be
>> integrated in a stable git tree (I mean before we can base our work on
>> top of it). So, in the meantime, what should I do to help and make
>> things go forward? to be quite frank, I would be interested to have a
>> working DMA enabled device soon ;-)
> 
> Me too, but unfortunately, I was busy trying to add irq_domain and
> fixing issues with SPARSE_IRQ on OMAP :-(

Been there, loved that ;-)

>> Do you think that 3.4 is out of reach?
> 
> Maybe not, from the comments, it looks like we should add a .xlate
> callback to allow any custom parsing of the DMA nodes attributes.
> 
> I'll be more than happy, if you can finalize that patch :-)

I will try to figure out what I can understand from the irq mechanism of
.xlate and try to see if I can implement it on top of your patch.

I will keep you informed...

Bye,

>> Best regards,
>>
>>> Signed-off-by: Benoit Cousson<[email-masked]>
>>> Cc: Grant Likely<[email-masked]>
>>> Cc: Rob Herring<[email-masked]>
>>> ---
>>>   Documentation/devicetree/bindings/dma/dma.txt |   44 +++++++++
>>>   drivers/of/Kconfig                            |    5 +
>>>   drivers/of/Makefile                           |    1 +
>>>   drivers/of/dma.c                              |  130
>>> +++++++++++++++++++++++++
>>>   include/linux/of_dma.h                        |   49 +++++++++
>>>   5 files changed, 229 insertions(+), 0 deletions(-)
>>>   create mode 100644 Documentation/devicetree/bindings/dma/dma.txt
>>>   create mode 100644 drivers/of/dma.c
>>>   create mode 100644 include/linux/of_dma.h
>>>
>>> diff --git a/Documentation/devicetree/bindings/dma/dma.txt
>>> b/Documentation/devicetree/bindings/dma/dma.txt
>>> new file mode 100644
>>> index 0000000..7f2a301
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/dma/dma.txt
>>> @@ -0,0 +1,44 @@
>>> +* Generic DMA Controller and DMA request bindings
>>> +
>>> +Generic binding to provide a way for a driver to retrieve the
>>> +DMA request line that goes from an IP to a DMA controller.
>>> +
>>> +
>>> +* DMA controller
>>> +
>>> +Required properties:
>>> +    - dma-controller: Mark the device as a DMA controller
>>> +    - #dma-cells: Number of cell for each DMA line, must be one.
>>> +
>>> +
>>> +Example:
>>> +
>>> +    sdma: dma-controller at 48000000 {
>>> +        compatible = "ti,sdma-omap4"
>>> +        reg =<0x48000000 0x1000>;
>>> +        interrupts =<12>;
>>> +        dma-controller;
>>> +        #dma-cells =<1>;
>>> +    };
>>> +
>>> +
>>> +
>>> +* DMA client
>>> +
>>> +Client drivers should specify the DMA request numbers using a
>>> phandle to
>>> +the controller + the DMA request number on that controller.
>>> +
>>> +Required properties:
>>> +    - dma-request: List of pair phandle + dma-request per line
>>> +    - dma-request-names: list of strings in the same order as the
>>> dma-request
>>> +      in the dma-request property.
>>> +
>>> +
>>> +Example:
>>> +
>>> +    i2c1: i2c at 1 {
>>> +        ...
>>> +        dma-request =<&sdma 2&sdma 3>;
>>> +        dma-request-names = "tx", "rx";
>>> +        ...
>>> +    };
>>> diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig
>>> index 268163d..7d1f06b 100644
>>> --- a/drivers/of/Kconfig
>>> +++ b/drivers/of/Kconfig
>>> @@ -90,4 +90,9 @@ config OF_PCI_IRQ
>>>       help
>>>         OpenFirmware PCI IRQ routing helpers
>>>
>>> +config OF_DMA
>>> +    def_bool y
>>> +    help
>>> +      Device Tree DMA routing helpers
>>> +
>>>   endmenu # OF
>>> diff --git a/drivers/of/Makefile b/drivers/of/Makefile
>>> index a73f5a5..d08443b 100644
>>> --- a/drivers/of/Makefile
>>> +++ b/drivers/of/Makefile
>>> @@ -12,3 +12,4 @@ obj-$(CONFIG_OF_SELFTEST) += selftest.o
>>>   obj-$(CONFIG_OF_MDIO)    += of_mdio.o
>>>   obj-$(CONFIG_OF_PCI)    += of_pci.o
>>>   obj-$(CONFIG_OF_PCI_IRQ)  += of_pci_irq.o
>>> +obj-$(CONFIG_OF_DMA)  += dma.o
>>> diff --git a/drivers/of/dma.c b/drivers/of/dma.c
>>> new file mode 100644
>>> index 0000000..d4927e2
>>> --- /dev/null
>>> +++ b/drivers/of/dma.c
>>> @@ -0,0 +1,130 @@
>>> +/*
>>> + * Device tree helpers for DMA request / controller
>>> + *
>>> + * Based on of_gpio.c
>>> + *
>>> + * Copyright (C) 2012 Texas Instruments Incorporated -
>>> http://www.ti.com/
>>> + *
>>> + * This program is free software; you can redistribute it and/or modify
>>> + * it under the terms of the GNU General Public License version 2 as
>>> + * published by the Free Software Foundation.
>>> + */
>>> +
>>> +#include<linux/device.h>
>>> +#include<linux/err.h>
>>> +#include<linux/module.h>
>>> +#include<linux/of.h>
>>> +#include<linux/of_dma.h>
>>> +
>>> +/**
>>> + * of_get_dma_request() - Get a DMA request number and
>>> dma-controller node
>>> + * @np:        device node to get DMA request from
>>> + * @propname:    property name containing DMA specifier(s)
>>> + * @index:    index of the DMA request
>>> + * @ctrl_np:    a device_node pointer to fill in
>>> + *
>>> + * Returns DMA number along to the dma controller node, or one of
>>> the errno
>>> + * value on the error condition. If @ctrl_np is not NULL the
>>> function also
>>> + * fills in the DMA controller device_node pointer.
>>> + */
>>> +int of_get_dma_request(struct device_node *np, int index,
>>> +               struct device_node **ctrl_np)
>>> +{
>>> +    int ret = -EINVAL;
>>> +    struct of_phandle_args dma_spec;
>>> +
>>> +    ret = of_parse_phandle_with_args(np, "dma-request", "#dma-cells",
>>> +                     index,&dma_spec);
>>> +    if (ret) {
>>> +        pr_debug("%s: can't parse dma property\n", __func__);
>>> +        goto err0;
>>> +    }
>>> +
>>> +    if (dma_spec.args_count>  0)
>>> +        ret = dma_spec.args[0];
>>> +
>>> +    if (ctrl_np)
>>> +        *ctrl_np = dma_spec.np;
>>> +    else
>>> +        of_node_put(dma_spec.np);
>>> +
>>> +err0:
>>> +    pr_debug("%s exited with status %d\n", __func__, ret);
>>> +    return ret;
>>> +}
>>> +EXPORT_SYMBOL(of_get_dma_request);
>>> +
>>> +/**
>>> + * of_dma_count - Count DMA requests for a device
>>> + * @np:        device node to count DMAs for
>>> + *
>>> + * The function returns the count of DMA requests specified for a node.
>>> + *
>>> + * Note that the empty DMA specifiers counts too. For example,
>>> + *
>>> + * dma-request =<0
>>> + *&sdma 1
>>> + *                0
>>> + *&sdma 3>;
>>> + *
>>> + * defines four DMAs (so this function will return 4), two of which
>>> + * are not specified.
>>> + */
>>> +unsigned int of_dma_count(struct device_node *np)
>>> +{
>>> +    unsigned int cnt = 0;
>>> +
>>> +    do {
>>> +        int ret;
>>> +
>>> +        ret = of_parse_phandle_with_args(np, "dma-request",
>>> +                         "#dma-cells", cnt, NULL);
>>> +        /* A hole in the dma-request =<>  counts anyway. */
>>> +        if (ret<  0&&  ret != -EEXIST)
>>> +            break;
>>> +    } while (++cnt);
>>> +
>>> +    return cnt;
>>> +}
>>> +EXPORT_SYMBOL(of_dma_count);
>>> +
>>> +/**
>>> + * of_dma_to_resource - Decode a node's DMA and return it as a resource
>>> + * @dev: pointer to device tree node
>>> + * @index: zero-based index of the DMA request
>>> + * @r: pointer to resource structure to return result into.
>>> + *
>>> + * Using a resource to export a DMA request number to a driver should
>>> + * be used only for legacy purpose and on system when only one DMA
>>> controller
>>> + * is present.
>>> + * The proper and only scalable way is to use the native
>>> of_get_dma_request API
>>> + * in order retrieve both the DMA controller device node and the DMA
>>> request
>>> + * line for that controller.
>>> + */
>>> +int of_dma_to_resource(struct device_node *dev, int index, struct
>>> resource *r)
>>> +{
>>> +    const char *name = NULL;
>>> +    int dma;
>>> +
>>> +    if (!r)
>>> +        return -EINVAL;
>>> +
>>> +    dma = of_get_dma_request(dev, index, NULL);
>>> +    if (dma<  0)
>>> +        return dma;
>>> +
>>> +    /*
>>> +     * Get optional "dma-request-names" property to add a name
>>> +     * to the resource.
>>> +     */
>>> +    of_property_read_string_index(dev, "dma-request-names", index,
>>> +                &name);
>>> +
>>> +    r->start = dma;
>>> +    r->end = dma;
>>> +    r->flags = IORESOURCE_DMA;
>>> +    r->name = name ? name : dev->full_name;
>>> +
>>> +    return dma;
>>> +}
>>> +EXPORT_SYMBOL_GPL(of_dma_to_resource);
>>> diff --git a/include/linux/of_dma.h b/include/linux/of_dma.h
>>> new file mode 100644
>>> index 0000000..575163d
>>> --- /dev/null
>>> +++ b/include/linux/of_dma.h
>>> @@ -0,0 +1,49 @@
>>> +/*
>>> + * OF helpers for DMA request / controller
>>> + *
>>> + * Based on of_gpio.h
>>> + *
>>> + * Copyright (C) 2012 Texas Instruments Incorporated -
>>> http://www.ti.com/
>>> + *
>>> + * This program is free software; you can redistribute it and/or modify
>>> + * it under the terms of the GNU General Public License version 2 as
>>> + * published by the Free Software Foundation.
>>> + */
>>> +
>>> +#ifndef __LINUX_OF_DMA_H
>>> +#define __LINUX_OF_DMA_H
>>> +
>>> +#include<linux/of.h>
>>> +
>>> +struct device_node;
>>> +
>>> +#ifdef CONFIG_OF_GPIO
>>> +
>>> +extern int of_get_dma_request(struct device_node *np, int index,
>>> +               struct device_node **ctrl_np);
>>> +extern unsigned int of_dma_count(struct device_node *np);
>>> +extern int of_dma_to_resource(struct device_node *dev, int index,
>>> +                  struct resource *r);
>>> +
>>> +#else /* CONFIG_OF_DMA */
>>> +
>>> +static int of_get_dma_request(struct device_node *np, int index,
>>> +                  struct device_node **ctrl_np);
>>> +{
>>> +    return -ENOSYS;
>>> +}
>>> +
>>> +static inline unsigned int of_dma_count(struct device_node *np)
>>> +{
>>> +    return 0;
>>> +}
>>> +
>>> +static int of_dma_to_resource(struct device_node *dev, int index,
>>> +                  struct resource *r);
>>> +{
>>> +    return -ENOSYS;
>>> +}
>>> +
>>> +#endif /* CONFIG_OF_DMA */
>>> +
>>> +#endif /* __LINUX_OF_DMA_H */
>>
>>
> 
> 

-- 
Nicolas Ferre