Re: [PATCH v2 10/10] dt-bindings: Add DSIv2 documentation

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On 11/21/2015 1:29 AM, Rob Herring wrote:
+Stephen

On Wed, Nov 18, 2015 at 9:24 AM, Archit Taneja <architt@xxxxxxxxxxxxxx> wrote:
Hi Rob,

On 11/18/2015 6:48 PM, Rob Herring wrote:

+dt list

On Wed, Nov 18, 2015 at 4:55 AM, Archit Taneja <architt@xxxxxxxxxxxxxx>
wrote:

Add additional property info needed for DSIv2 DT.


Please use get_maintainers.pl.


Sorry about that, missed out doing that posting this time.


Signed-off-by: Archit Taneja <architt@xxxxxxxxxxxxxx>
---
   Documentation/devicetree/bindings/display/msm/dsi.txt | 10 +++++++++-
   1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/display/msm/dsi.txt
b/Documentation/devicetree/bindings/display/msm/dsi.txt
index f344b9e..ca65a34 100644
--- a/Documentation/devicetree/bindings/display/msm/dsi.txt
+++ b/Documentation/devicetree/bindings/display/msm/dsi.txt
@@ -13,18 +13,25 @@ Required properties:
   - power-domains: Should be <&mmcc MDSS_GDSC>.
   - clocks: device clocks
     See Documentation/devicetree/bindings/clocks/clock-bindings.txt for
details.
-- clock-names: the following clocks are required:
+- clock-names: these vary based on the DSI version. For DSI6G:
     * "bus_clk"
     * "byte_clk"
+  * "byte_clk_src


This sounds like the parent of byte_clk. Is that really a clock within
the block?


byte_clk_src isn't in the block, but byte_clk_src's parent is one of
the PLLs in this block. We take this clock so that we can re-parent
it to an appropriate PLL. The decision of what PLL to choose needs to
be done by the DSI block's driver.

Seems like abuse to me. The list of clocks should match what are
inputs to the block, not what the driver happens to need. Without a
full understanding of the clock tree here, I don't have a suggestion.
Maybe Stephen does.

We don't need specify byte_clk_src (and other xyz_clk_src clocks) via
DT. There is a static link set up between byte_clk and byte_clk_src by
our clock driver that never changes. We can retrieve it in the driver
itself using clk_get_parent(byte_clk). This way we stick to only
input clocks.

Stephen, does that sound okay?


     * "core_clk"
     * "core_mmss_clk"
     * "iface_clk"
     * "mdp_core_clk"
     * "pixel_clk"
+  * "pixel_clk_src"
+  For DSIv2, we need a few more:


What is the overall order of clocks? As listed?


Order in which the driver does clk_get? It uses the clock
name to get each one individually, so the order doesn't matter
as such.

The order in DT. You may use the names, but the order should still be specified.

Okay. I'll cross check and make sure the order is as in our DT files.

Archit


Rob
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