Re: [PATCH v2 5/5] dt-bindings: net: ipq4019-mdio: Document ipq5332 platform
From: Jie Luo
Date: Fri Dec 15 2023 - 06:42:59 EST
On 12/15/2023 6:53 PM, Krzysztof Kozlowski wrote:
On 15/12/2023 11:40, Jie Luo wrote:
On 12/15/2023 6:37 PM, Krzysztof Kozlowski wrote:
On 15/12/2023 11:33, Jie Luo wrote:
+ cmn-reference-clock:
+ oneOf:
+ - items:
+ - enum:
+ - 0 # CMN PLL reference internal 48MHZ
+ - 1 # CMN PLL reference external 25MHZ
+ - 2 # CMN PLL reference external 31250KHZ
+ - 3 # CMN PLL reference external 40MHZ
+ - 4 # CMN PLL reference external 48MHZ
+ - 5 # CMN PLL reference external 50MHZ
+ - 6 # CMN PLL reference internal 96MHZ
Why is this not represented by an element of the clocks property?
This property is for the reference clock source selection of CMN PLL,
CMN PLL generates the different clock rates for the different Ethernet
blocks, this CMN PLL configuration is not located in the GCC, so the
clock framework can't be used, which is the general hardware register
instead of RCG register for GCC.
I don't see how the clock being provided by the "GCC" (whatever that is)
or by some other clock controller or fixed clock makes a difference.
Why can't the other clock provider be represented in the devicetree?
cmn-reference-clock is for selecting the reference clock source for the
whole Ethernet block, which is just the standalone configure register.
Sure, you are aware though that all clocks are just configure registers?
Which clocks are these mentioned in the property? From where do they come?
Anyway, property is in existing form is not correct - this is not a
generic property.
This property cmn-reference-clock is just the hardware register
configuration, since the different IPQ platform needs to select
the different reference clock source for the CMN PLL block that
provides the various clock outputs to the all kinds of Ethernet
devices, which is not from GCC provider.
AGAIN: where do the clocks come from? Which device generates them?
Oh, OK, the reference clock is from wifi that provides 48MHZ to
Ethernet block.
Then WiFi should be providing you the clock and this device should be
clock consumer, right?
Yes, wifi provides 48MHz clock to CMM PLL block, there is no GCC
for this 48MHZ clock output, it is the hardware PIN connection.
All clocks are some hardware pin connections.
Best regards,
Krzysztof
Yes, all reference clocks here are from hardware pin connection.