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authorSimon Glass <>2015-03-05 12:25:25 -0700
committerSimon Glass <>2015-04-16 19:27:43 -0600
commitff3e077bd23c37c83d01aad105e528194e33d75e (patch)
tree187c45a9cc100b90e9d3dc3cf623178e928f73c1 /doc
parentaab6724c90c39e1f599d4ee6354c9f2cf553dc61 (diff)
dm: pci: Add a uclass for PCI
Add a uclass for PCI controllers and a generic one for PCI devices. Adjust the 'pci' command and the existing PCI support to work with this new uclass. Keep most of the compatibility code in a separate file so that it can be removed one day. TODO: Add more header file comments to the new parts of pci.h Signed-off-by: Simon Glass <>
Diffstat (limited to 'doc')
1 files changed, 70 insertions, 0 deletions
diff --git a/doc/driver-model/pci-info.txt b/doc/driver-model/pci-info.txt
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+++ b/doc/driver-model/pci-info.txt
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+PCI with Driver Model
+How busses are scanned
+Any config read will end up at pci_read_config(). This uses
+uclass_get_device_by_seq() to get the PCI bus for a particular bus number.
+Bus number 0 will need to be requested first, and the alias in the device
+tree file will point to the correct device:
+ aliases {
+ pci0 = &pci;
+ };
+ pci: pci-controller {
+ compatible = "sandbox,pci";
+ ...
+ };
+If there is no alias the devices will be numbered sequentially in the device
+The call to uclass_get_device by seq() will cause the PCI bus to be probed.
+This does a scan of the bus to locate available devices. These devices are
+bound to their appropriate driver if available. If there is no driver, then
+they are bound to a generic PCI driver which does nothing.
+After probing a bus, the available devices will appear in the device tree
+under that bus.
+Note that this is all done on a lazy basis, as needed, so until something is
+touched on PCI it will not be probed.
+PCI devices can appear in the device tree. If they do this serves to specify
+the driver to use for the device. In this case they will be bound at
+With sandbox we need a device emulator for each device on the bus since there
+is no real PCI bus. This works by looking in the device tree node for a
+driver. For example:
+ pci@1f,0 {
+ compatible = "pci-generic";
+ reg = <0xf800 0 0 0 0>;
+ emul@1f,0 {
+ compatible = "sandbox,swap-case";
+ };
+ };
+This means that there is a 'sandbox,swap-case' driver at that bus position.
+Note that the first cell in the 'reg' value is the bus/device/function. See
+PCI_BDF() for the encoding (it is also specified in the IEEE Std 1275-1994
+PCI bus binding document, v2.1)
+When this bus is scanned we will end up with something like this:
+`- * pci-controller @ 05c660c8, 0
+ `- pci@1f,0 @ 05c661c8, 63488
+ `- emul@1f,0 @ 05c662c8
+When accesses go to the pci@1f,0 device they are forwarded to its child, the
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