On 01/13/2017 05:56 PM, Boris Brezillon wrote:

On Fri, 13 Jan 2017 17:44:12 +0100
Marek Vasut [off-list ref] wrote:

quoted

On 01/13/2017 05:28 PM, Boris Brezillon wrote:

quoted

On Fri, 13 Jan 2017 17:13:55 +0100
Marek Vasut [off-list ref] wrote:
  

quoted

On 01/13/2017 04:12 PM, Matthias Brugger wrote:  

quoted

On 13/01/17 15:17, Boris Brezillon wrote:    

quoted

On Fri, 13 Jan 2017 15:13:29 +0800
Guochun Mao [off-list ref] wrote:
   

quoted

Add Mediatek nor flash node.

Signed-off-by: Guochun Mao <redacted>
---
 arch/arm/boot/dts/mt2701-evb.dts |   25 +++++++++++++++++++++++++
 arch/arm/boot/dts/mt2701.dtsi    |   12 ++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/arch/arm/boot/dts/mt2701-evb.dts

b/arch/arm/boot/dts/mt2701-evb.dts
index 082ca88..85e5ae8 100644

--- a/arch/arm/boot/dts/mt2701-evb.dts
+++ b/arch/arm/boot/dts/mt2701-evb.dts

@@ -24,6 +24,31 @@
     };
 };

+&nor_flash {
+    pinctrl-names = "default";
+    pinctrl-0 = <&nor_pins_default>;
+    status = "okay";
+    flash at 0 {
+        compatible = "jedec,spi-nor";
+        reg = <0>;
+    };
+};
+
+&pio {
+    nor_pins_default: nor {
+        pins1 {
+            pinmux = <MT2701_PIN_240_EXT_XCS__FUNC_EXT_XCS>,
+                 <MT2701_PIN_241_EXT_SCK__FUNC_EXT_SCK>,
+                 <MT2701_PIN_239_EXT_SDIO0__FUNC_EXT_SDIO0>,
+                 <MT2701_PIN_238_EXT_SDIO1__FUNC_EXT_SDIO1>,
+                 <MT2701_PIN_237_EXT_SDIO2__FUNC_EXT_SDIO2>,
+                 <MT2701_PIN_236_EXT_SDIO3__FUNC_EXT_SDIO3>;
+            drive-strength = <MTK_DRIVE_4mA>;
+            bias-pull-up;
+        };
+    };
+};
+
 &uart0 {
     status = "okay";
 };

diff --git a/arch/arm/boot/dts/mt2701.dtsi

b/arch/arm/boot/dts/mt2701.dtsi
index bdf8954..1eefce4 100644

--- a/arch/arm/boot/dts/mt2701.dtsi
+++ b/arch/arm/boot/dts/mt2701.dtsi

@@ -227,6 +227,18 @@
         status = "disabled";
     };

+    nor_flash: spi at 11014000 {
+        compatible = "mediatek,mt2701-nor",
+                 "mediatek,mt8173-nor";    

Why define both here? Is "mediatek,mt8173-nor" really providing a
subset of the features supported by "mediatek,mt2701-nor"?
   

I think even if the ip block is the same, we should provide both
bindings, just in case in the future we find out that mt2701 has some
hidden bug, feature or bug-feature. This way even if we update the
driver, we stay compatible with older device tree blobs in the wild.

We can drop the mt2701-nor in the bindings definition if you want.   

Oh, sorry, I misunderstood. What I meant is that if you want to
list/support all possible compatibles, maybe you should just put one
compatible in your DT and patch your driver (+ binding doc) to define
all of them.  

Uh, what ? I lost you here :-)

quoted

quoted

This exactly. We should have a DT compat in the form:
compatible = "vendor,<soc>-block", "vendor,<oldest-compat-soc>-block";
Then if we find a problem in the future, we can match on the
"vendor,<soc>-block" and still support the old DTs.  

Not sure it's only in term of whose IP appeared first. My understanding
is that it's a way to provide inheritance. For example:

	"<soc-vendor>,<ip-version>", "<ip-vendor>,<ip-version>";

or

	"<soc-vendor>,<full-featured-ip-version>","<soc-vendor>,<basic-feature-ip-version>";

BTW, which one is the oldest between mt8173 and mt2701? :-)  

And that's another thing and I agree with you, but I don't think that's
what we're discussing in this thread. But (!), OT, I think we should
codify the rules in Documentation/ . This discussion came up multiple
times recently.

And my question still stands, what do we put into the DT here, IMO
compatible = "mediatek,mt2701-nor", "mediatek,mt8173-nor";

I'd say

	compatible = "mediatek,mt8173-nor";

because both compatible are referring to very specific IP version. It's
not the same as

But then you don't have the ability to handle a block in this particular
SoC in case there's a bug found in it in the future,
so IMO it should be:

compatible = "mediatek,mt2701-nor", "mediatek,mt8173-nor";

	compatible = "mediatek,mt8173-nor", "mediatek,mt81xx-nor";

This doesn't look right, since here we add two new compatibles ...

where you clearly have a generic compatible which is overloaded by a
specific one.

But anyway, I'm not the one taking the decision here, let's wait for DT
maintainers reviews.

quoted

and what goes into the binding document ? I guess both too ?

If both exist, they should be both documented.

-- 
Best regards,
Marek Vasut