Re: [PATCH] ARM: dts: keystone: use one to one address translations under netcp

From: Murali Karicheri
Date: Thu Sep 03 2015 - 15:19:12 EST

On 09/03/2015 10:26 AM, Tony Lindgren wrote:
* santosh shilimkar <santosh.shilimkar@xxxxxxxxxx> [150902 08:55]:

I suspected the same. I know back then we started with SERDES code
with NETCP but as you already know, its a separate block which
is needed for NIC card to work. Its more of phy and hence its
having different address space is not surprising.

The point Santosh is making here though is that any drivers
tinkering with registers belonging to a separate hardware block
is a recipe for a long term maintenance nightmare with mysterious

That is what we want to avoid as well. If I interpret your statement correctly, you don't want SerDes driver update the register of say SGMII, right? But we will have to based on the hardware design. So it can't be a standalone device driver IMO and it has to be part of the respective peripheral device driver.

bugs popping up as things are not clocked or powered properly
or become racy with other drivers.

Each hardware block needs to have it's own driver and then the
drivers can communicate using some Linux generic APIs like clock,
regulator, phy, or mailbox frameworks.

That depends on what your definition of a hardware block is. Inside NetCP, there are many hardware blocks that work together to provide the NIC functionality, and SerDes is one of them. Where ever possible, we have separate drivers :- knav qmss, knav pkt dma, ethss, mdio etc. Ethss driver manages Eth subsystem that includes SGMII and SerDes. Unfortunately SerDes is tightly integrated with ethss and taking it out as a separate driver (Say Phy) is not a good idea. We will posting an RFC for this soon and probably we can discuss it more then.

Probably we will fold this into the RFC series to give this a better context.




Murali Karicheri
Linux Kernel, Keystone
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