[RFC PATCH 1/2] of: Add generic device tree DMA helpers
Cousson, Benoit
b-cousson at ti.com
Thu Feb 23 21:03:30 EST 2012
Salut Nico,
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 :-(
> 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 :-)
Thanks,
Benoit
>
> Best regards,
>
>> Signed-off-by: Benoit Cousson<b-cousson at ti.com>
>> Cc: Grant Likely<grant.likely at secretlab.ca>
>> Cc: Rob Herring<rob.herring at calxeda.com>
>> ---
>> 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 */
>
>
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