[PATCH v2 07/11] of: populate new device_d::dma_coherent attribute

[Ahmad Fatoum]

So far, whether device DMA is coherent was a one-time global decision.
This is insufficient, because some platforms:

 - are cache coherent, while the architecture isn't in general, e.g.
   barebox support for ARM with CONFIG_MMU=y assumes non-coherent DMA,
   but LS1046A can be fully coherent.

 - have a mix of devices that snoop caches and devices that don't
   (StarFive JH7100).

To enable dev_dma_(map|unmap)_single to take the correct device-specific
action with regards to cache maintenance, provide dev_is_dma_coherent()
with semantics similar to what Linux provides.

Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
---
v1 -> v2:
  - make dma_coherent a boolean (Sascha)
  - add dma_coherent unconditionally (Sascha)
  - Only print dma_coherent status for devices with OF node
---
 commands/devinfo.c    |  4 ++++
 drivers/of/platform.c |  1 +
 include/driver.h      | 22 ++++++++++++++++++++++
 3 files changed, 27 insertions(+)

diff --git a/commands/devinfo.c b/commands/devinfo.c
index aeb9c5533931..6001b00cfac8 100644
--- a/commands/devinfo.c
+++ b/commands/devinfo.c
@@ -105,6 +105,10 @@ static int do_devinfo(int argc, char *argv[])
 		if (dev->of_node) {
 			struct device *main_dev = dev->of_node->dev;
 
+			printf("DMA Coherent: %s%s\n",
+			       dev_is_dma_coherent(dev) ? "true" : "false",
+			       dev->dma_coherent == DEV_DMA_COHERENCE_DEFAULT ? " (default)" : "");
+
 			printf("Device node: %pOF", dev->of_node);
 			if (!main_dev) {
 			       printf(" (unpopulated)\n");
diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index edfeb192d434..060fa3458bd2 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -129,6 +129,7 @@ static void of_dma_configure(struct device *dev, struct device_node *np)
 	}
 
 	dev->dma_offset = offset;
+	dev->dma_coherent = of_dma_is_coherent(np);
 }
 
 /**
diff --git a/include/driver.h b/include/driver.h
index b37b0ab192a3..c23404ca16fb 100644
--- a/include/driver.h
+++ b/include/driver.h
@@ -25,6 +25,12 @@ struct platform_device_id {
 	unsigned long driver_data;
 };
 
+enum dev_dma_coherence {
+	DEV_DMA_COHERENCE_DEFAULT = 0,
+	DEV_DMA_COHERENT,
+	DEV_DMA_NON_COHERENT,
+};
+
 /** @brief Describes a particular device present in the system */
 struct device {
 	/*! This member (and 'type' described below) is used to match
@@ -45,6 +51,8 @@ struct device {
 	 * something like eth0 or nor0. */
 	int id;
 
+	enum dev_dma_coherence dma_coherent;
+
 	struct resource *resource;
 	int num_resources;
 
@@ -720,6 +728,20 @@ static inline struct device_node *dev_of_node(struct device *dev)
 	return IS_ENABLED(CONFIG_OFDEVICE) ? dev->of_node : NULL;
 }
 
+static inline bool dev_is_dma_coherent(struct device *dev)
+{
+	switch (dev->dma_coherent) {
+	case DEV_DMA_NON_COHERENT:
+		return false;
+	case DEV_DMA_COHERENT:
+		return true;
+	case DEV_DMA_COHERENCE_DEFAULT:
+		break;
+	}
+
+	return IS_ENABLED(CONFIG_ARCH_DMA_DEFAULT_COHERENT);
+}
+
 static inline void *dev_get_priv(const struct device *dev)
 {
 	return dev->priv;
-- 
2.39.2