Hi Caleb,
On Wed, 21 Aug 2024 at 08:49, Caleb Connolly caleb.connolly@linaro.org wrote:
On 21/08/2024 16:37, Simon Glass wrote:
Hi Caleb,
On Wed, 21 Aug 2024 at 08:11, Caleb Connolly caleb.connolly@linaro.org wrote:
Hi Simon,
+U_BOOT_DRIVER(gcc_sc7280) = {
.name = "gcc_sc7280",.id = UCLASS_NOP,.of_match = gcc_sc7280_of_match,.bind = qcom_cc_bind,.flags = DM_FLAG_PRE_RELOC | DM_FLAG_DEFAULT_PD_CTRL_OFF,+};
This should use driver model, with a UCLASS_CLK and UCLASS_RESET
Please refer to qcom_cc_bind() which binds the clock, reset, and power domain drivers.
Gosh, why? Are these devices not in the devicetree?
They are, the gcc block contains clock, reset, and pd parts. On Linux this is not an issue because a single device can be multiple different classes (e..g when you register a reset you do it for a device) whereas U-Boot requires a device per class.
e.g. see devm_reset_controller_register() in Linux, it populates a struct reset_controller_dev which references the struct device created for the node. In U-Boot you have to create a new device which _is_ the reset controller.
OK, I see. Rockchip has a CRU (Clock & Reset Unit) which uses syscon to access registers. The clock driver 'owns' the node in U-Boot and it manually binds a reset driver. It isn't great, either.
Looking at drivers/clk/qcom/clock-sdm845.c (for example), I can't actually find "qcom,gcc-sdm845" (for example) in U-Boot, except as a binding. Can you please point me to the node?
Re devm_reset_controller_register(), yes the U-Boot driver model is a lot more regular, e.g. we don't really want drivers creating their own struct udevice. We want all devices to be created automatically by the devicetree and most memory allocations to be done automatically. This helps to reduce code size and execution time. You probably know all this :-)
To a significant degree, the devicetree bindings are created without much thought to efficient operation in U-Boot. I hope that eventually this might change.
Anyway, with the devicetree we have, I wonder how we could do this better?
Some ideas:
1. Allow DM to bind multiple devices to each devicetree node, perhaps as a Kconfig option (to avoid time penalty for all boards), or by requiring a new DM_FLAG_MULTI_NODE flag. The devices would then be independent, with no common parent device
2. As 1 but have DM create a parent 'UCLASS_MULTI' device automatically. I am thinking that we should have a new uclass for these things, or rename the NOP uclass. This option would allow easy access to the parent device, if needed.
3. Implement devices which are in more than one uclass. There would still be a primary uclass, but others can be added too. This would involve declaring a list of secondary uclasses in the U_BOOT_DRIVER() macro. We would then have a struct dmtag_node for each secondary uclass, containing the ID and the uclass pointer. Certain functions would need to be updated to support this, and again it could be behind a Kconfig.
What do you think?
Regards, Simon