On 12/17/2014 04:56 PM, Arnd Bergmann wrote:
On Wednesday 17 December 2014 13:02:23 Murali Karicheri wrote:
Now, in Kernel, parent device's DMA parameters has to be applied to
the child as is - to enable DMA support for the device. Usually this
is happened in places where parent device manually instantiates child
device such as in drivers/pci/probe.c (pci_device_add() for example).
Now DMA configuration is represented in device data structure not only
by DMA mask and DMA params, it also includes dma_pfn_offset at least.
Hence introduce common dma_get_parent_cfg() helper to apply dma
configuration from parent to child, and use __weak to allow arch to
override it if needed.
Signed-off-by: Murali Karicheri<m-karicheri2@xxxxxx>
---
drivers/base/dma-mapping.c | 18 ++++++++++++++++++
include/linux/dma-mapping.h | 3 +++
2 files changed, 21 insertions(+)
diff --git a/drivers/base/dma-mapping.c b/drivers/base/dma-mapping.c
index 9e8bbdd..5322426 100644
--- a/drivers/base/dma-mapping.c
+++ b/drivers/base/dma-mapping.c
@@ -339,3 +339,21 @@ void dma_common_free_remap(void *cpu_addr, size_t size, unsigned long vm_flags)
vunmap(cpu_addr);
}
#endif
+
+int __weak dma_get_parent_cfg(struct device *dev, struct device *parent)
+{
+ struct device *temp = parent;
+
+ if (!temp)
+ temp = dev->parent;
+
+ if (temp&& is_device_dma_capable(temp)) {
+ dev->dma_mask = temp->dma_mask;
+ dev->coherent_dma_mask = temp->coherent_dma_mask;
As discussed, setting the pointers like this is always wrong,
so don't do it.
What's wrong with using arch_setup_dma_ops() from PCI as suggested
previously?
Arnd
Arnd,
Thanks for the review.
I had originally written a code based on that line as below. But
dma-ranges property is also used by ppc and other architectures in the
pci device DT node. So I wasn't sure how this code impact PCI driver
functionality on those platforms. Hence used a simpler change as all
that is needed for keystone is to get the dma_pfn_offset rightly set in
the pci slave device.
Initially I had a function implemented as below for this in of_pci.c.
+ * of_pci_dma_configure - Setup DMA configuration for a pci device
+ * @dev: pci device to apply DMA configuration
+ *
+ * Try to get devices's DMA configuration from DT and update it
+ * accordingly. This is a similar to of_dma_configure() for platform
+ * devices.
+ *
+ */
+void of_pci_dma_configure(struct pci_dev *dev)
+{
+ struct device *host_bridge, *parent;
+ struct pci_bus *bus = dev->bus;
+ u64 dma_addr, paddr, size;
+ int ret;
+
+ while (!pci_is_root_bus(bus))
+ bus = bus->parent;
+ host_bridge = bus->bridge;
+
+ parent = host_bridge->parent;
+ if (parent->of_node) {
+ /*
+ * if dma-coherent property exist, call arch hook to setup
+ * dma coherent operations.
+ */
+ if (of_dma_is_coherent(parent->of_node)) {
+ set_arch_dma_coherent_ops(&dev->dev);
+ dev_info(&dev->dev, "device is dma coherent\n");
+ }
+
+ /*
+ * if dma-ranges property doesn't exist - just return else
+ * setup the dma offset
+ */
+ ret = of_dma_get_range(parent->of_node, &dma_addr,
&paddr, &size);
+ if (ret < 0) {
+ dev_info(&dev->dev, "no dma range information to
setup\n");
+ printk("no dma range information to setup\n");
+ return;
+ }
+
+ /* DMA ranges found. Calculate and set dma_pfn_offset */
+ dev->dev.dma_pfn_offset = PFN_DOWN(paddr - dma_addr);
+ dev_info(&dev->dev, "dma_pfn_offset(%#08lx)\n",
dev->dev.dma_pfn_offset);
+ }
+}
+EXPORT_SYMBOL_GPL(of_pci_dma_configure);
and then called from pci/probe.c as
@@ -1527,6 +1528,9 @@ void pci_device_add(struct pci_dev *dev, struct
pci_bus *bus)
dev->dev.dma_parms = &dev->dma_parms;
dev->dev.coherent_dma_mask = 0xffffffffull;
+ /* Get the DMA configuration from root bridge's parent if present */
+ of_pci_dma_configure(dev);
If you think this is a better way to implement this, I can work on a
patch set using this approach. Let me know.
--
Murali Karicheri
Linux Kernel, Texas Instruments
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