Hi Martin,

Thanks for your comment.

On 8/25/2019 5:11 AM, Martin Blumenstingl wrote:

Hi Dilip,

quoted

Add driver for the reset controller present on Intel
Lightening Mountain (LGM) SoC for performing reset
management of the devices present on the SoC. Driver also
registers a reset handler to peform the entire device reset.

[...]

quoted

+static const struct of_device_id intel_reset_match[] = {
+	{ .compatible = "intel,rcu-lgm" },
+	{}
+};

how is this IP block differnet from the one used in many Lantiq SoCs?
there is already an upstream driver for the RCU IP block on the Lantiq
SoCs: drivers/reset/reset-lantiq.c

some background:
Lantiq was started as a spinoff from Infineon in 2009. Intel then
acquired Lantiq in 2015. source: [0]
Intel is re-using some of the IP blocks from the MIPS Lantiq SoCs
(Intel even has some own MIPS SoCs as part of the Lantiq acquisition,
typically used for PON/GPON/ADSL/VDSL capable network devices).
Thus I think it is likely that the new "Lightening Mountain" SoCs use
an updated version of the Lantiq RCU IP.

I would not say there is a fundamental difference since reset is a 
really simple

stuff from all reset drivers.  However, it did have some difference

from existing reset-lantiq.c since SoC becomes more and more complex.

1. reset-lantiq.c use index instead of register offset + bit position.

index reset is good for a small system (< 64). However, it will become very

difficult to use if you have  > 100 reset. So we use register offset + 
bit position

2. reset-lantiq.c does not support device restart which is part of the 
reset in

old lantiq SoC. It moved this part into arch/mips/lantiq directory.

3. reset-lantiqc reset callback doesn't implement what hardware implemented

function. In old SoCs, some bits in the same register can be hardware 
reset clear.

It just call assert + assert. For these SoCs, we should only call 
assert, hardware

will auto deassert.

4. Code not optimized and intel internal review not assessed.

Based on the above findings, I would suggest reset-lantiq.c to move to 
reset-intel-syscon.c

What is your opinion?


Chuanhua

Martin


[0] https://wikidevi.com/wiki/Lantiq