Hi,

On Thu, 19 Aug 2021 at 18:23, Marcel Holtmann [off-list ref] wrote:

quoted

This is an RFC of the proposed power sequencer subsystem. This is a
generification of the MMC pwrseq code. The subsystem tries to abstract
the idea of complex power-up/power-down/reset of the devices.

The primary set of devices that promted me to create this patchset is
the Qualcomm BT+WiFi family of chips. They reside on serial+platform
interfaces (older generations) or on serial+PCIe (newer generations).
They require a set of external voltage regulators to be powered on and
(some of them) have separate WiFi and Bluetooth enable GPIOs.

This patchset being an RFC tries to demonstrate the approach, design and
usage of the pwrseq subsystem. Following issues are present in the RFC
at this moment but will be fixed later if the overall approach would be
viewed as acceptable:

- No documentation
  While the code tries to be self-documenting proper documentation
  would be required.

- Minimal device tree bindings changes
  There are no proper updates for the DT bindings (thus neither Rob
  Herring nor devicetree are included in the To/Cc lists). The dt
  schema changes would be a part of v1.

- Lack of proper PCIe integration
  At this moment support for PCIe is hacked up to be able to test the
  PCIe part of qca6390. Proper PCIe support would require automatically
  powering up the devices before the scan basing on the proper device
  structure in the device tree.

----------------------------------------------------------------
Dmitry Baryshkov (15):
     power: add power sequencer subsystem
     pwrseq: port MMC's pwrseq drivers to new pwrseq subsystem
     mmc: core: switch to new pwrseq subsystem
     ath10k: add support for pwrseq sequencing
     Bluetooth: hci_qca: merge qca_power into qca_serdev
     Bluetooth: hci_qca: merge init paths
     Bluetooth: hci_qca: merge qca_power_on with qca_regulators_init
     Bluetooth: hci_qca: futher rework of power on/off handling
     Bluetooth: hci_qca: add support for pwrseq

any chance you can try to abandon patching hci_qca. The serdev support in hci_uart is rather hacking into old line discipline code and it is not aging well. It is really becoming a mess.

I wanted to stay away from rewriting the BT code. But... New driver
would have a bonus point that I don't have to be compatible with old
bindings. In fact we can even make it the other way around: let the
old driver always use regulators and make the new driver support only
the pwrseq. Then it should be possible to drop the old hci_qca driver
together with dropping the old bindings.

I would say that the Qualcomm serial devices could use a separate standalone serdev driver. A while I send an RFC for a new serdev driver.

https://www.spinics.net/lists/linux-bluetooth/msg74918.html

Any reason why your driver stayed as an RFC and never made it into the
kernel? Do you plan to revive your old RFCs on H:4 and H:5?

There I had the idea that simple vendor specifics can be in that driver (like the Broadcom part I added there), but frankly the QCA specifics are a bit too specific and it should be a separate driver. However I think this would be a good starting point.

In general a H:4 based Bluetooth driver is dead simple with the help of h4_recv.h helper we have in the kernel. The complicated part is the power management pieces or any vendor specific low-power protocol they are running on that serial line. And since you are touching this anyway, doing a driver from scratch might be lot simpler and cleaner. It would surely help all the new QCA device showing up in the future.

-- 
With best wishes
Dmitry