[PATCH RFC v8 0/5] MPC512x DMA slave s/g support, OF DMA lookup

[PATCH RFC v8 0/5] MPC512x DMA slave s/g support, OF DMA lookup

[Alexander Popov]

2013/7/14 Gerhard Sittig <gsi-ynQEQJNshbs@public.gmane.org>:
> this series
> - introduces slave s/g support (that's support for DMA transfers which
>    involve peripherals in contrast to mem-to-mem transfers)
> - adds device tree based lookup support for DMA channels
> - combines floating patches and related feedback which already covered
>    several aspects of what the suggested LPB driver needs, to demonstrate
>    how integration might be done
> - carries Q&D SD card support to enable another DMA client during test,
>    while this patch needs to get dropped upon pickup

Changes in v2:
> - re-order mpc8308 related code paths for improved readability, no
>    change in behaviour, introduction of symbolic channel names here
>    already
> - squash 'execute() start condition' and 'terminate all' into the
>    introduction of 'slave s/g prep' and 'device control' support; refuse
>    s/g lists with more than one item since slave support is operational
>    yet proper s/g support is missing (can get addressed later)
> - always start transfers from software on MPC8308 as there are no
>    external request lines for peripheral flow control
> - drop dt-bindings header file and symbolic channel names in OF nodes

Changes in v3 and v4:
 Part 1/5:
 - use #define instead of enum since individual channels don't require
    special handling.
 Part 2/5:
 - add a flag "will_access_peripheral" to DMA transfer descriptor
    according recommendations of Gerhard Sittig.
    This flag is set in mpc_dma_prep_memcpy() and mpc_dma_prep_slave_sg()
    and is evaluated in mpc_dma_execute() to choose a type of start for
    the transfer.
 - prevent descriptors of transfers which involve peripherals from
    being chained together;
    each of such transfers needs hardware initiated start.
 - add locking while working with struct mpc_dma_chan
    according recommendations of Lars-Peter Clausen.
 - remove default nbytes value. Client kernel modules must set
    src_maxburst and dst_maxburst fields of struct dma_slave_config (dmaengine.h).

Changes in v5:
 Part 2/5:
 - add and improve comments;
 - improve the code moving transfer descriptors from 'queued' to 'active' list
    in mpc_dma_execute();
 - allow mpc_dma_prep_slave_sg() to run with non-empty 'active' list;
 - take 'mdesc' back to 'free' list in case of error in mpc_dma_prep_slave_sg();
 - improve checks of the transfer parameters;
 - provide the default value for 'maxburst' in mpc_dma_device_control().

Changes in v6:
 Part 2/5:
 - remove doubtful comment;
 - fix coding style issues;
 - set default value for 'maxburst' to 1 which applies to most cases;
 Part 3/5:
 - use dma_get_slave_channel() instead of dma_request_channel()
    in new function of_dma_xlate_by_chan_id() according recommendations of
    Arnd Bergmann;
 Part 4/5:
 - set DMA_PRIVATE flag for MPC512x DMA controller since its driver relies on
    of_dma_xlate_by_chan_id() which doesn't use dma_request_channel()
    any more; (removed in v7)
 - resolve little patch conflict;
 Part 5/5:
 - resolve little patch conflict;

Changes in v7:
 Part 2:
 - improve comment;
 Part 4:
 - split in two separate patches. Part 4/6 contains device tree
    binding document and in part 5/6 MPC512x DMA controller is registered
    for device tree channel lookup;
 - remove setting DMA_PRIVATE flag for MPC512x DMA controller from part 5/6;

Changes in v8:
 Part 2:
 - improve comments;
 - fix style issues;
 Part 6:
 - remove since it has become obsolete;

> known issues:
> - it's yet to get confirmed whether MPC8308 can use slave support or
>    whether the DMA controller's driver shall actively reject it, the
>    information that's available so far suggests that peripheral transfers
>    to IP bus attached I/O is useful and shall not get blocked right away
 - adding support for transfers which don't increment the RAM address or
    do increment the peripheral "port's" address is easy with
    this implementation; but which options of the common API
    should be used for specifying such transfers?
2014/02/13 Gerhard Sittig <gsi-ynQEQJNshbs@public.gmane.org>:
> - The MPC512x DMA completely lacks a binding document, so one
>    should get added.
> - The MPC8308 hardware is similar and can re-use the MPC512x
>    binding, which should be stated.
> - The Linux implementation currently has no OF based channel
>    lookup support, so '#dma-cells' is "a future feature".  I guess
>    the binding can and should already discuss the feature,
>    regardless of whether all implementations support it.


Alexander Popov (3):
  dma: mpc512x: reorder mpc8308 specific instructions
  dma: mpc512x: add support for peripheral transfers
  dma: of: Add common xlate function for matching by channel id

Gerhard Sittig (2):
  dma: mpc512x: add device tree binding document
  dma: mpc512x: register for device tree channel lookup

 .../devicetree/bindings/dma/mpc512x-dma.txt        |  55 ++++
 arch/powerpc/boot/dts/mpc5121.dtsi                 |   1 +
 drivers/dma/mpc512x_dma.c                          | 298 +++++++++++++++++++--
 drivers/dma/of-dma.c                               |  35 +++
 include/linux/of_dma.h                             |   4 +
 5 files changed, 368 insertions(+), 25 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/dma/mpc512x-dma.txt

-- 
1.8.4.2

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[PATCH RFC v8 3/5] dma: of: Add common xlate function for matching by channel id

[Alexander Popov]

This patch adds a new common OF dma xlate callback function which will match a
channel by it's id. The binding expects one integer argument which it will use to
lookup the channel by the id.

Unlike of_dma_simple_xlate this function is able to handle a system with
multiple DMA controllers. When registering the of dma provider with
of_dma_controller_register a pointer to the dma_device struct which is
associated with the dt node needs to passed as the data parameter.
New function will use this pointer to match only channels which belong to the
specified DMA controller.

Signed-off-by: Alexander Popov <a13xp0p0v88-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
 drivers/dma/of-dma.c   | 35 +++++++++++++++++++++++++++++++++++
 include/linux/of_dma.h |  4 ++++
 2 files changed, 39 insertions(+)

diff --git a/drivers/dma/of-dma.c b/drivers/dma/of-dma.c
index e8fe9dc..d5fbeaa 100644
--- a/drivers/dma/of-dma.c
+++ b/drivers/dma/of-dma.c
@@ -218,3 +218,38 @@ struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
 			&dma_spec->args[0]);
 }
 EXPORT_SYMBOL_GPL(of_dma_simple_xlate);
+
+/**
+ * of_dma_xlate_by_chan_id - Translate dt property to DMA channel by channel id
+ * @dma_spec:	pointer to DMA specifier as found in the device tree
+ * @of_dma:	pointer to DMA controller data
+ *
+ * This function can be used as the of xlate callback for DMA driver which wants
+ * to match the channel based on the channel id. When using this xlate function
+ * the #dma-cells propety of the DMA controller dt node needs to be set to 1.
+ * The data parameter of of_dma_controller_register must be a pointer to the
+ * dma_device struct the function should match upon.
+ *
+ * Returns pointer to appropriate dma channel on success or NULL on error.
+ */
+struct dma_chan *of_dma_xlate_by_chan_id(struct of_phandle_args *dma_spec,
+					 struct of_dma *ofdma)
+{
+	struct dma_device *dev = ofdma->of_dma_data;
+	struct dma_chan *chan, *candidate = NULL;
+
+	if (!dev || dma_spec->args_count != 1)
+		return NULL;
+
+	list_for_each_entry(chan, &dev->channels, device_node)
+		if (chan->chan_id == dma_spec->args[0]) {
+			candidate = chan;
+			break;
+		}
+
+	if (!candidate)
+		return NULL;
+
+	return dma_get_slave_channel(candidate);
+}
+EXPORT_SYMBOL_GPL(of_dma_xlate_by_chan_id);
diff --git a/include/linux/of_dma.h b/include/linux/of_dma.h
index ae36298..56bc026 100644
--- a/include/linux/of_dma.h
+++ b/include/linux/of_dma.h
@@ -41,6 +41,8 @@ extern struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
 						     const char *name);
 extern struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
 		struct of_dma *ofdma);
+extern struct dma_chan *of_dma_xlate_by_chan_id(struct of_phandle_args *dma_spec,
+		struct of_dma *ofdma);
 #else
 static inline int of_dma_controller_register(struct device_node *np,
 		struct dma_chan *(*of_dma_xlate)
@@ -66,6 +68,8 @@ static inline struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_s
 	return NULL;
 }
 
+#define of_dma_xlate_by_chan_id NULL
+
 #endif
 
 #endif /* __LINUX_OF_DMA_H */
-- 
1.8.4.2

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[PATCH RFC v8 4/5] dma: mpc512x: add device tree binding document

[Alexander Popov]

From: Gerhard Sittig <gsi-ynQEQJNshbs@public.gmane.org>

introduce a device tree binding document for the MPC512x DMA controller

Signed-off-by: Gerhard Sittig <gsi-ynQEQJNshbs@public.gmane.org>
[ a13xp0p0v88-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org: turn this into a separate patch ]
---
 .../devicetree/bindings/dma/mpc512x-dma.txt        | 55 ++++++++++++++++++++++
 1 file changed, 55 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/dma/mpc512x-dma.txt

diff --git a/Documentation/devicetree/bindings/dma/mpc512x-dma.txt b/Documentation/devicetree/bindings/dma/mpc512x-dma.txt
new file mode 100644
index 0000000..a4867d5
--- /dev/null
+++ b/Documentation/devicetree/bindings/dma/mpc512x-dma.txt
@@ -0,0 +1,55 @@
+* Freescale MPC512x DMA Controller
+
+The DMA controller in the Freescale MPC512x SoC can move blocks of
+memory contents between memory and peripherals or memory to memory.
+
+Refer to the "Generic DMA Controller and DMA request bindings" description
+in the dma.txt file for a more detailled discussion of the binding.  The
+MPC512x DMA engine binding follows the common scheme, but doesn't provide
+support for the optional channels and requests counters (those values are
+derived from the detected hardware features) and has a fixed client
+specifier length of 1 integer cell (the value is the DMA channel, since
+the DMA controller uses a fixed assignment of request lines per channel).
+
+
+DMA controller node properties:
+
+Required properties:
+- compatible:		should be "fsl,mpc5121-dma"
+- reg:			address and size of the DMA controller's register set
+- interrupts:		interrupt spec for the DMA controller
+
+Optional properties:
+- #dma-cells:		must be <1>, describes the number of integer cells
+			needed to specify the 'dmas' property in client nodes,
+			strongly recommended since common client helper code
+			uses this property
+
+Example:
+
+	dma0: dma@14000 {
+		compatible = "fsl,mpc5121-dma";
+		reg = <0x14000 0x1800>;
+		interrupts = <65 0x8>;
+		#dma-cells = <1>;
+	};
+
+
+Client node properties:
+
+Required properties:
+- dmas:			list of DMA specifiers, consisting each of a handle
+			for the DMA controller and integer cells to specify
+			the channel used within the DMA controller
+- dma-names:		list of identifier strings for the DMA specifiers,
+			client device driver code uses these strings to
+			have DMA channels looked up at the controller
+
+Example:
+
+	sdhc@1500 {
+		compatible = "fsl,mpc5121-sdhc";
+		/* ... */
+		dmas = <&dma0 30>;
+		dma-names = "rx-tx";
+	};
-- 
1.8.4.2

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[PATCH RFC v8 5/5] dma: mpc512x: register for device tree channel lookup

[Alexander Popov]

From: Gerhard Sittig <gsi-ynQEQJNshbs@public.gmane.org>

register the controller for device tree based lookup of DMA channels
(non-fatal for backwards compatibility with older device trees) and
provide the '#dma-cells' property in the shared mpc5121.dtsi file

Signed-off-by: Gerhard Sittig <gsi-ynQEQJNshbs@public.gmane.org>
[ a13xp0p0v88-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org: resolve little patch conflict and put
  MPC512x DMA controller bindings document to a separate patch ]
---
 arch/powerpc/boot/dts/mpc5121.dtsi |  1 +
 drivers/dma/mpc512x_dma.c          | 21 ++++++++++++++++++---
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/boot/dts/mpc5121.dtsi b/arch/powerpc/boot/dts/mpc5121.dtsi
index 2c0e155..7f9d14f 100644
--- a/arch/powerpc/boot/dts/mpc5121.dtsi
+++ b/arch/powerpc/boot/dts/mpc5121.dtsi
@@ -498,6 +498,7 @@
 			compatible = "fsl,mpc5121-dma";
 			reg = <0x14000 0x1800>;
 			interrupts = <65 0x8>;
+			#dma-cells = <1>;
 		};
 	};
 
diff --git a/drivers/dma/mpc512x_dma.c b/drivers/dma/mpc512x_dma.c
index 8f504cb..d9f8740 100644
--- a/drivers/dma/mpc512x_dma.c
+++ b/drivers/dma/mpc512x_dma.c
@@ -52,6 +52,7 @@
 #include <linux/of_address.h>
 #include <linux/of_device.h>
 #include <linux/of_irq.h>
+#include <linux/of_dma.h>
 #include <linux/of_platform.h>
 
 #include <linux/random.h>
@@ -1018,11 +1019,23 @@ static int mpc_dma_probe(struct platform_device *op)
 	/* Register DMA engine */
 	dev_set_drvdata(dev, mdma);
 	retval = dma_async_device_register(dma);
-	if (retval) {
-		devm_free_irq(dev, mdma->irq, mdma);
-		irq_dispose_mapping(mdma->irq);
+	if (retval)
+		goto out_irq;
+
+	/* register with OF helpers for DMA lookups (nonfatal) */
+	if (dev->of_node) {
+		retval = of_dma_controller_register(dev->of_node,
+						    of_dma_xlate_by_chan_id,
+						    mdma);
+		if (retval)
+			dev_warn(dev, "could not register for OF lookup\n");
 	}
 
+	return 0;
+
+out_irq:
+	devm_free_irq(dev, mdma->irq, mdma);
+	irq_dispose_mapping(mdma->irq);
 	return retval;
 }
 
@@ -1031,6 +1044,8 @@ static int mpc_dma_remove(struct platform_device *op)
 	struct device *dev = &op->dev;
 	struct mpc_dma *mdma = dev_get_drvdata(dev);
 
+	if (dev->of_node)
+		of_dma_controller_free(dev->of_node);
 	dma_async_device_unregister(&mdma->dma);
 	devm_free_irq(dev, mdma->irq, mdma);
 	irq_dispose_mapping(mdma->irq);
-- 
1.8.4.2

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Re: [PATCH RFC v8 5/5] dma: mpc512x: register for device tree channel lookup

[Andy Shevchenko]

On Mon, 2014-02-24 at 15:09 +0400, Alexander Popov wrote:
> From: Gerhard Sittig <gsi-ynQEQJNshbs@public.gmane.org>
> 
> register the controller for device tree based lookup of DMA channels
> (non-fatal for backwards compatibility with older device trees) and
> provide the '#dma-cells' property in the shared mpc5121.dtsi file
> 
> Signed-off-by: Gerhard Sittig <gsi-ynQEQJNshbs@public.gmane.org>
> [ a13xp0p0v88-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org: resolve little patch conflict and put
>   MPC512x DMA controller bindings document to a separate patch ]
> ---
>  arch/powerpc/boot/dts/mpc5121.dtsi |  1 +
>  drivers/dma/mpc512x_dma.c          | 21 ++++++++++++++++++---
>  2 files changed, 19 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/boot/dts/mpc5121.dtsi b/arch/powerpc/boot/dts/mpc5121.dtsi
> index 2c0e155..7f9d14f 100644
> --- a/arch/powerpc/boot/dts/mpc5121.dtsi
> +++ b/arch/powerpc/boot/dts/mpc5121.dtsi
> @@ -498,6 +498,7 @@
>  			compatible = "fsl,mpc5121-dma";
>  			reg = <0x14000 0x1800>;
>  			interrupts = <65 0x8>;
> +			#dma-cells = <1>;
>  		};
>  	};
>  
> diff --git a/drivers/dma/mpc512x_dma.c b/drivers/dma/mpc512x_dma.c
> index 8f504cb..d9f8740 100644
> --- a/drivers/dma/mpc512x_dma.c
> +++ b/drivers/dma/mpc512x_dma.c
> @@ -52,6 +52,7 @@
>  #include <linux/of_address.h>
>  #include <linux/of_device.h>
>  #include <linux/of_irq.h>
> +#include <linux/of_dma.h>
>  #include <linux/of_platform.h>
>  
>  #include <linux/random.h>
> @@ -1018,11 +1019,23 @@ static int mpc_dma_probe(struct platform_device *op)
>  	/* Register DMA engine */
>  	dev_set_drvdata(dev, mdma);
>  	retval = dma_async_device_register(dma);
> -	if (retval) {
> -		devm_free_irq(dev, mdma->irq, mdma);
> -		irq_dispose_mapping(mdma->irq);
> +	if (retval)
> +		goto out_irq;
> +
> +	/* register with OF helpers for DMA lookups (nonfatal) */
> +	if (dev->of_node) {
> +		retval = of_dma_controller_register(dev->of_node,
> +						    of_dma_xlate_by_chan_id,
> +						    mdma);
> +		if (retval)
> +			dev_warn(dev, "could not register for OF lookup\n");
>  	}
>  
> +	return 0;
> +
> +out_irq:
> +	devm_free_irq(dev, mdma->irq, mdma);

Something wrong either with devm_request_irq() or you don't need to call
devm_free_irq() explicitly. Once we already try to discuss this earlier
in this mailing list with Lars-Peter(?), though there were no solution
how to keep devm_*_irq usability.

> +	irq_dispose_mapping(mdma->irq);
>  	return retval;
>  }
>  
> @@ -1031,6 +1044,8 @@ static int mpc_dma_remove(struct platform_device *op)
>  	struct device *dev = &op->dev;
>  	struct mpc_dma *mdma = dev_get_drvdata(dev);
>  
> +	if (dev->of_node)
> +		of_dma_controller_free(dev->of_node);
>  	dma_async_device_unregister(&mdma->dma);
>  	devm_free_irq(dev, mdma->irq, mdma);
>  	irq_dispose_mapping(mdma->irq);


-- 
Andy Shevchenko <andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Intel Finland Oy

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Re: [PATCH RFC v8 5/5] dma: mpc512x: register for device tree channel lookup

[Alexander Popov]

Hello Andy.

2014-02-24 17:08 GMT+04:00 Andy Shevchenko <andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>:
> On Mon, 2014-02-24 at 15:09 +0400, Alexander Popov wrote:
>> @@ -1018,11 +1019,23 @@ static int mpc_dma_probe(struct platform_device *op)
>>       /* Register DMA engine */
>>       dev_set_drvdata(dev, mdma);
>>       retval = dma_async_device_register(dma);
>> -     if (retval) {
>> -             devm_free_irq(dev, mdma->irq, mdma);
>> -             irq_dispose_mapping(mdma->irq);
>> +     if (retval)
>> +             goto out_irq;
>> +
>> +     /* register with OF helpers for DMA lookups (nonfatal) */
>> +     if (dev->of_node) {
>> +             retval = of_dma_controller_register(dev->of_node,
>> +                                                 of_dma_xlate_by_chan_id,
>> +                                                 mdma);
>> +             if (retval)
>> +                     dev_warn(dev, "could not register for OF lookup\n");
>>       }
>>
>> +     return 0;
>> +
>> +out_irq:
>> +     devm_free_irq(dev, mdma->irq, mdma);
>
> Something wrong either with devm_request_irq() or you don't need to call
> devm_free_irq() explicitly. Once we already try to discuss this earlier
> in this mailing list with Lars-Peter(?), though there were no solution
> how to keep devm_*_irq usability.

Thanks, I've read this discussion. It seems that the current code doesn't do
anything bad, though devm_request_irq() and devm_free_irq() can be changed
to request_irq() and free_irq() accordingly. Do you think it's worth being done
in a separate patch in this series?

>> +     irq_dispose_mapping(mdma->irq);
>>       return retval;
>>  }
>>
>> @@ -1031,6 +1044,8 @@ static int mpc_dma_remove(struct platform_device *op)
>>       struct device *dev = &op->dev;
>>       struct mpc_dma *mdma = dev_get_drvdata(dev);
>>
>> +     if (dev->of_node)
>> +             of_dma_controller_free(dev->of_node);
>>       dma_async_device_unregister(&mdma->dma);
>>       devm_free_irq(dev, mdma->irq, mdma);
>>       irq_dispose_mapping(mdma->irq);

Best regards,
Alexander
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