summaryrefslogtreecommitdiff
path: root/doc
diff options
context:
space:
mode:
authorSimon Glass <sjg@chromium.org>2019-09-25 08:56:10 -0600
committerBin Meng <bmeng.cn@gmail.com>2019-10-08 13:57:41 +0800
commit9b69ba4a787209da59e69fd4e411ab6561b0447f (patch)
tree6afb6789182055037ce58fb76b2c9abe3469eb28 /doc
parente77663cf747b4c01fc72e3af1c72996a0f586613 (diff)
downloadu-boot-9b69ba4a787209da59e69fd4e411ab6561b0447f.tar.gz
pci: sandbox: Move the emulators into their own node
Sandbox pci works using emulation drivers which are currently children of the pci device: pci-controller { pci@1f,0 { compatible = "pci-generic"; reg = <0xf800 0 0 0 0>; emul@1f,0 { compatible = "sandbox,swap-case"; }; }; }; In this case the emulation device is attached to pci device on address f800 (device 1f, function 0) and provides the swap-case functionality. However this is not ideal, since every device on a PCI bus has a child device. This is only really the case for sandbox, but we want to avoid special-case code for sandbox. Worse, child devices cannot be probed before their parents. This forces us to use 'find' rather than 'get' to obtain the emulator device. In fact the emulator devices are never probed. There is code in sandbox_pci_emul_post_probe() which tries to track when emulators are active, but at present this does not work. A better approach seems to be to add a separate node elsewhere in the device tree, an 'emulation parent'. This could be given a bogus address (such as -1) to hide the emulators away from the 'pci' command, but it seems better to keep it at the root node to avoid such hacks. Then we can use a phandle to point from the device to the correct emulator, and only on sandbox. The code to find an emulator does not interfere with normal pci operation. Add a new UCLASS_PCI_EMUL_PARENT uclass which allows finding an emulator given a bus, and finding a bus given an emulator. Update the existing device trees and the code for finding an emulator. This brings PCI emulators more into line with I2C. Signed-off-by: Simon Glass <sjg@chromium.org> Reviewed-by: Bin Meng <bmeng.cn@gmail.com> Tested-by: Bin Meng <bmeng.cn@gmail.com> [bmeng: fix 3 typos in the commit message; encode bus number in the labels of swap_case_emul nodes; mention commit 4345998ae9df in sandbox_pci_get_emul()] Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Diffstat (limited to 'doc')
-rw-r--r--doc/driver-model/pci-info.rst23
1 files changed, 12 insertions, 11 deletions
diff --git a/doc/driver-model/pci-info.rst b/doc/driver-model/pci-info.rst
index d93ab8b61d..f39ff990a6 100644
--- a/doc/driver-model/pci-info.rst
+++ b/doc/driver-model/pci-info.rst
@@ -113,14 +113,17 @@ Sandbox
-------
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::
-
+is no real PCI bus. This works by looking in the device tree node for an
+emulator driver. For example::
pci@1f,0 {
compatible = "pci-generic";
reg = <0xf800 0 0 0 0>;
- emul@1f,0 {
+ sandbox,emul = <&emul_1f>;
+ };
+ pci-emul {
+ compatible = "sandbox,pci-emul-parent";
+ emul_1f: emul@1f,0 {
compatible = "sandbox,swap-case";
};
};
@@ -130,14 +133,16 @@ 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)
+The pci-emul node should go outside the pci bus node, since otherwise it will
+be scanned as a PCI device, causing confusion.
+
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
+ `- emul@1f,0 @ 05c662c8
-When accesses go to the pci@1f,0 device they are forwarded to its child, the
-emulator.
+When accesses go to the pci@1f,0 device they are forwarded to its emulator.
The sandbox PCI drivers also support dynamic driver binding, allowing device
driver to declare the driver binding information via U_BOOT_PCI_DEVICE(),
@@ -164,7 +169,3 @@ When this bus is scanned we will end up with something like this::
pci [ + ] pci_sandbo |-- pci-controller1
pci_emul [ ] sandbox_sw | |-- sandbox_swap_case_emul
pci_emul [ ] sandbox_sw | `-- sandbox_swap_case_emul
-
-Note the difference from the statically declared device nodes is that the
-device is directly attached to the host controller, instead of via a container
-device like pci@1f,0.