On Mon, Sep 01, 2025 at 08:15:24PM +0530, Manivannan Sadhasivam wrote:
On Mon, Sep 01, 2025 at 04:50:02PM GMT, Siddharth Vadapalli wrote:
On Mon, Sep 01, 2025 at 12:14:51PM +0530, Manivannan Sadhasivam wrote:
On Mon, Sep 01, 2025 at 11:51:33AM GMT, Siddharth Vadapalli wrote:
[...]
If I understand correctly, are you suggesting the following?
j721e_pcie_probe() pm_runtime_set_active() pm_runtime_enable() ret = j721e_pcie_ctrl_init(pcie); /* * PCIe Controller should be powered off here, but is there * a way to ensure that it has been powered off? */ => Program the strap settings and return to j721e_pcie_probe() /* Power on the PCIe Controller now */ ret = pm_runtime_get_sync(dev);
This pm_runtime_get_sync() should be part of j721e_pcie_ctrl_init() where you do power off, program strap and power on.
This should not be part of probe() as by that time, controller is already powered on. So pm_runtime_set_active() and pm_runtime_enable() should be enough to convey the state of the device to PM core.
I have tried out the suggestion in the following manner:
j721e_pcie_probe() ... pm_runtime_set_active(dev); pm_runtime_enable(dev); ret = j721e_pcie_ctrl_init(pcie); ... within j721e_pcie_ctrl_init() ret = pm_runtime_put_sync(dev); /* Program Strap Settings */ ret = pm_runtime_get_sync(dev); ... ... exit probe
Since a 'pm_runtime_get_sync()' hasn't yet been invoked prior to the section where 'pm_runtime_put_sync()' is invoked, it leads to a ref-count underflow error at runtime. Please let me know if I am missing something.
Doh... At the start of probe(), device PM usage_count will be 0. So we cannot decrement it without incrementing it.
Could you try below sequence?
probe() ... pm_runtime_set_active() pm_runtime_enable() j721e_pcie_ctrl_init() ... pm_runtime_get() /* Just increment usage_count */ pm_runtime_put_sync() /* ask PM core to turn off */ /* program strap setting */ pm_runtime_get_sync() /* ask PM core to turn on */ pm_runtime_put_noidle() /* balance the usage_count without suspending the device */ ...
The above sequence powers off the controller at the point in time that the strap settings are programmed. 'pm_runtime_get_sync()' is powering on the controller afterwards. However, the 'pm_runtime_put_noidle()' at the end is causing the controller to be powered off again leading to a crash. Removing 'pm_runtime_put_noidle()' results in a functional sequence.
Please consider the existing sequence prior to this patch:
probe() ... pm_runtime_enable() pm_runtime_get_sync() => usage_count is 1 ... exit probe
With the suggested sequence above, we have:
probe() ... pm_runtime_set_active() pm_runtime_enable() j721e_pcie_ctrl_init() ... pm_runtime_get() => usage_count is 1 pm_runtime_put_sync() => usage_count is 0 /* Controller is powered off now */ /* Strap settings are programmed */ pm_runtime_get_sync() => usage_count is 1 /* Controller is powered on now */ pm_runtime_put_noidle() => usage_count is 0 /* Controller is powered off in a while */ ... /* Crash is observed aroung this point before probe finishes */
Please let me know if the fix is to drop 'pm_runtime_put_noidle()' from the above sequence.
Regards, Siddharth.