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

From: Murali Karicheri
Date: Wed Sep 02 2015 - 12:36:31 EST


On 09/02/2015 11:50 AM, santosh shilimkar wrote:
On 9/2/2015 8:31 AM, Kwok, WingMan wrote:

-----Original Message-----
From: santosh.shilimkar@xxxxxxxxxx [mailto:santosh.shilimkar@xxxxxxxxxx]
Sent: Tuesday, September 01, 2015 5:19 PM
To: Kwok, WingMan; robh+dt@xxxxxxxxxx; pawel.moll@xxxxxxx;
mark.rutland@xxxxxxx; ijc+devicetree@xxxxxxxxxxxxxx;
linux@xxxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; linux-arm-
kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
Cc: Karicheri, Muralidharan
Subject: Re: [PATCH] ARM: dts: keystone: use one to one address
under netcp

On 9/1/15 1:28 PM, WingMan Kwok wrote:
Network subsystem NetCP in Keystone-2 devices includes some HW blocks
that are memory mapped to ranges outside that of the NetCP itself.
Thus address space of a child node of the NetCP node needs to be
mapped 1:1 onto the parent address space. Hence empty ranges
should be used under the NetCP node.

Signed-off-by: WingMan Kwok <w-kwok2@xxxxxx>
arch/arm/boot/dts/k2e-netcp.dtsi | 8 +++-----
arch/arm/boot/dts/k2hk-netcp.dtsi | 14 ++++++--------
arch/arm/boot/dts/k2l-netcp.dtsi | 8 +++-----
3 files changed, 12 insertions(+), 18 deletions(-)

diff --git a/arch/arm/boot/dts/k2e-netcp.dtsi b/arch/arm/boot/dts/k2e-
index b13b3c9..e103ed9 100644
--- a/arch/arm/boot/dts/k2e-netcp.dtsi
+++ b/arch/arm/boot/dts/k2e-netcp.dtsi
@@ -111,9 +111,7 @@ netcp: netcp@24000000 {
compatible = "ti,netcp-1.0";
#address-cells = <1>;
#size-cells = <1>;
- /* NetCP address range */
- ranges = <0 0x24000000 0x1000000>;
+ ranges;

What blocks are we talking here. We need to increase the
range if the current range isn't covering entire NETCP
address space. Removing range isn't a solution.

The Serdes. It is a HW block inside the NetCP but its address
space starts from 0x0232a000. We can change the base in the
ranges property to include the serdes. But then offsets of
other HW blocks that are within the NetCP address range will be
relative to this new base and are not as documented in the HW
user guides.

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.

Using Phy interface is not acceptable to the subsystem maintainer based on the communication I had on this. Also the Phy here is tighly coupled with the hardware block it is working with. So this model is not right for SerDes driver as it require additional enhancements as described below if needs to be used.

The serdes initialization procedure requires checking the status in the hardware block (PCIe, 1G or 10G) and then taking corrective action. This means a Phy driver would require mapping of related hw address space (PCIe, 1G and 10G) as well which is already mapped by the hardware driver(PCIe, 1G and 10G). One solution is to treat this as a libray function that can be called from the respective hardware device driver. A device node of h/w device (PCIe or 1G) in such as looks like

pcie {

serdes@someaddress {
reg = <address of serdes>;

hw driver will call ks2_serdes_init(node, hw_base_address) to initialize the serdes. Other APIs can be added to enable/disable lane or shutdown etc. The libary will be added to drivers/soc/ti/ and used by various device drivers to initialize and use the phy. As the serdes is slightly integrated with the hardware block, IMO, this is a better approach than using the phy model. The API definitions will be added to include/linux/soc/ti/ folder.

The SerDes will use the firmware interface to download and configure the hardware block to use with PCIe/1G/10G/SRIO. I queried the linux forum on this and the response was that firmware interface can be used for this. The patch will be using the firmware interface instead of embedding magic values in the serdes driver.


IIRC, there was a plan to consolidate the serdes code together
since the PCIE also needs it. Irrespective of that, I suggest
you model the serdes address space in another node and fetch
it from there if that works for you. Please also add DTS
documentation if you are going ahead with that approach.


Murali Karicheri
Linux Kernel, Keystone
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