Re: [PATCH 1/1] of: add dma-mask binding

On 03/07/2012 11:34 AM, Jean-Christophe PLAGNIOL-VILLARD wrote:

On 10:59 Wed 07 Mar     , Rob Herring wrote:

quoted

On 03/07/2012 05:26 AM, Jean-Christophe PLAGNIOL-VILLARD wrote:

quoted

This will allow each device to specify its dma-mask
The microblaze architecture hook is keep temporary if no dma-mask is specified
int the DT

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj-sclMFOaUSTBWk0Htik3J/w@public.gmane.org>
---
 drivers/of/platform.c |   26 +++++++++++++++++++++++++-
 1 files changed, 25 insertions(+), 1 deletions(-)

diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index cae9477..bb22194 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c

@@ -121,6 +121,26 @@ void of_device_make_bus_id(struct device *dev)
 	dev_set_name(dev, "%s.%d", node->name, magic - 1);
 }
 
+static u64* of_get_dma_mask(struct device_node *np)
+{
+	const __be32 *prop;
+	int len;
+	u64 *dma_mask;
+
+	prop = of_get_property(np, "dma-mask", &len);

This would need some documentation. There is already "dma-ranges"
defined for OF which nay do what's needed.

what is dma-ranges I see no doc about it
but I don't think it could be used for the dma mask

See the ePAPR spec. It's a PowerPC doc, but parts still apply.

https://www.power.org/resources/downloads/Power_ePAPR_APPROVED_v1.1.pdf

There may also be something in OpenFirmware specs.

quoted

quoted

+
+	if (!prop)
+		return NULL;
+
+	dma_mask = kzalloc(sizeof(u64), GFP_KERNEL);

This seems kind of wasteful for 1 u64.

no choice dma_mask must be a pointer

quoted

quoted

+	if (!dma_mask)
+		return NULL;
+
+	*dma_mask = of_read_number(prop, len / 4);
+
+	return dma_mask;
+}
+
 /**
  * of_device_alloc - Allocate and initialize an of_device
  * @np: device node to assign to device

@@ -161,10 +181,14 @@ struct platform_device *of_device_alloc(struct device_node *np,
 		WARN_ON(of_irq_to_resource_table(np, res, num_irq) != num_irq);
 	}
 
+	dev->dev.dma_mask = of_get_dma_mask(np);
 	dev->dev.of_node = of_node_get(np);
+
 #if defined(CONFIG_MICROBLAZE)
-	dev->dev.dma_mask = &dev->archdata.dma_mask;

And doing it this way for didn't get a warm reception either:

http://lists.ozlabs.org/pipermail/devicetree-discuss/2011-April/005285.html

Do you really need this to be something other than ~0UL and if so does
it need to be per device or system wide?

You can solve this with bus notifiers in your at91 code. Here's an
example which I did (but no longer need):

static u64 highbank_dma_mask = DMA_BIT_MASK(32);

IIRC on at91 all of them that need it have a DMA_BIT_MASK(32)

quoted

static int highbank_platform_notifier(struct notifier_block *nb,
				  unsigned long event, void *__dev)
{
	struct device *dev = __dev;

	if (event != BUS_NOTIFY_ADD_DEVICE)
		return NOTIFY_DONE;

	if (of_device_is_compatible(dev->of_node, "calxeda,hb-nfc"))
		dev->dma_mask = &highbank_dma_mask;

execpt as example today I need it on 2 node (OHCI & EHCI)

I don't think there is any reason you can't point to a single value if a
system wide setting fits. If not, using a per device value here is
easily doable.

and if more device need I don't want to end up with more fixup

I really prefer to set it via DT

You don't have any h/w restrictions here and most ARM platforms don't,
so really this doesn't need to be solved with DT for the default case.

Rob