Re: [PATCH v3 2/5] ARM: NSP: add minimal Northstar Plus device tree

[Ray Jui]

On 8/30/2015 7:24 PM, Jon Mason wrote:
> On Fri, Aug 28, 2015 at 05:20:20PM -0700, Ray Jui wrote:
>>
>>
>> On 8/28/2015 4:47 PM, Jon Mason wrote:
>>> Add a very minimalistic set of Northstar Plus Device Tree files which
>>> describes the SoC and the BCM958625 implementation.  The perpherials
>>> described are:
>>>
>>> ARM Cortex A9 CPU
>>> 2 8250 UARTs
>>> ARM GIC
>>> PL310 L2 Cache
>>> ARM A9 Global timer
>>>
>>> Signed-off-by: Kapil Hali <kapilh@xxxxxxxxxxxx>
>>> Signed-off-by: Jon Mason <jonmason@xxxxxxxxxxxx>
>>> ---
>>>  arch/arm/boot/dts/Makefile       |   2 +
>>>  arch/arm/boot/dts/bcm-nsp.dtsi   | 120 +++++++++++++++++++++++++++++++++++++++
>>>  arch/arm/boot/dts/bcm958625k.dts |  57 +++++++++++++++++++
>>>  3 files changed, 179 insertions(+)
>>>  create mode 100644 arch/arm/boot/dts/bcm-nsp.dtsi
>>>  create mode 100644 arch/arm/boot/dts/bcm958625k.dts
>>>
>>> diff --git a/arch/arm/boot/dts/Makefile b/arch/arm/boot/dts/Makefile
>>> index 246473a..adb5732 100644
>>> --- a/arch/arm/boot/dts/Makefile
>>> +++ b/arch/arm/boot/dts/Makefile
>>> @@ -82,6 +82,8 @@ dtb-$(CONFIG_ARCH_BCM_CYGNUS) += \
>>>  dtb-$(CONFIG_ARCH_BCM_MOBILE) += \
>>>  	bcm28155-ap.dtb \
>>>  	bcm21664-garnet.dtb
>>> +dtb-$(CONFIG_ARCH_BCM_NSP) += \
>>> +	bcm958625k.dtb
>>>  dtb-$(CONFIG_ARCH_BERLIN) += \
>>>  	berlin2-sony-nsz-gs7.dtb \
>>>  	berlin2cd-google-chromecast.dtb \
>>> diff --git a/arch/arm/boot/dts/bcm-nsp.dtsi b/arch/arm/boot/dts/bcm-nsp.dtsi
>>> new file mode 100644
>>> index 0000000..f5f494f
>>> --- /dev/null
>>> +++ b/arch/arm/boot/dts/bcm-nsp.dtsi
>>> @@ -0,0 +1,120 @@
>>> +/*
>>> + *  BSD LICENSE
>>> + *
>>> + *  Copyright(c) 2015 Broadcom Corporation.  All rights reserved.
>>> + *
>>> + *  Redistribution and use in source and binary forms, with or without
>>> + *  modification, are permitted provided that the following conditions
>>> + *  are met:
>>> + *
>>> + *    * Redistributions of source code must retain the above copyright
>>> + *      notice, this list of conditions and the following disclaimer.
>>> + *    * Redistributions in binary form must reproduce the above copyright
>>> + *      notice, this list of conditions and the following disclaimer in
>>> + *      the documentation and/or other materials provided with the
>>> + *      distribution.
>>> + *    * Neither the name of Broadcom Corporation nor the names of its
>>> + *      contributors may be used to endorse or promote products derived
>>> + *      from this software without specific prior written permission.
>>> + *
>>> + *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
>>> + *  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
>>> + *  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
>>> + *  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
>>> + *  OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
>>> + *  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
>>> + *  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
>>> + *  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
>>> + *  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
>>> + *  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
>>> + *  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
>>> + */
>>> +
>>> +#include <dt-bindings/interrupt-controller/arm-gic.h>
>>> +#include <dt-bindings/interrupt-controller/irq.h>
>>> +
>>> +#include "skeleton.dtsi"
>>> +
>>> +/ {
>>> +	compatible = "brcm,nsp";
>>> +	model = "Broadcom Northstar Plus SoC";
>>> +	interrupt-parent = <&gic>;
>>> +
>>> +	mpcore {
>>> +		compatible = "simple-bus";
>>> +		ranges = <0x00000000 0x19020000 0x00003000>;
>>> +		#address-cells = <1>;
>>> +		#size-cells = <1>;
>>> +
>>> +		cpus {
>>> +			#address-cells = <1>;
>>> +			#size-cells = <0>;
>>> +
>>> +			cpu@0 {
>>> +				device_type = "cpu";
>>> +				compatible = "arm,cortex-a9";
>>> +				next-level-cache = <&L2>;
>>> +				reg = <0x0>;
>>> +			};
>>> +		};
>>> +
>>> +		L2: l2-cache {
>>> +			compatible = "arm,pl310-cache";
>>> +			reg = <0x2000 0x1000>;
>>> +			cache-unified;
>>> +			cache-level = <2>;
>>> +		};
>>> +
>>> +		gic: interrupt-controller@19021000 {
>>> +			compatible = "arm,cortex-a9-gic";
>>> +			#interrupt-cells = <3>;
>>> +			#address-cells = <0>;
>>> +			interrupt-controller;
>>> +			reg = <0x1000 0x1000>,
>>> +			      <0x0100 0x100>;
>>> +		};
>>> +
>>> +		timer@19020200 {
>>> +			compatible = "arm,cortex-a9-global-timer";
>>> +			reg = <0x0200 0x100>;
>>> +			interrupts = <GIC_PPI 11 IRQ_TYPE_LEVEL_HIGH>;
>>> +			clocks = <&periph_clk>;
>>> +		};
>>> +	};
>>> +
>>> +	clocks {
>>> +		#address-cells = <1>;
>>> +		#size-cells = <1>;
>>> +		ranges;
>>> +
>>> +		periph_clk: periph_clk {
>>> +			compatible = "fixed-clock";
>>> +			#clock-cells = <0>;
>>> +			clock-frequency = <500000000>;
>>> +		};
>>> +	};
>>> +
>>> +	apb {
>>> +		compatible = "arm,amba-bus", "simple-bus";
>>
>> Should "arm,amba-bus" has a separate bus node with AMBA compatible
>> devices declared in there (e.g, pl330, spi-pl022, and etc.) in the
>> future after they are brought up? To my best knowledge, "ns16550a" UART
>> is NOT an AMBA compatible device.
> 
> APB is an AMBA bus, so this part is accurate.  The block diagram of
> the SoC has the UARTs (and other perpherials) hanging off of the APB
> bus.  So, this organization follows the block diagram.

Okay so the "apb" node can be used for amba compatible devices
(arm,amba-bus) and/or simple platform devices (simple-bus). I guess
that's fine and I now see that there are some other dtsi also doing it
this way.

> While the
> UART drivers are not AMBA aware, there appears to be no issues with
> this layout (as the HW/drivers come up without issue). Unless there
> is an unforeseen issue with having non-AMBA aware devices on the DT
> AMBA bus, I would think it best to organize it to match the block
> disgram.
> 

UART runs fine because you also have "simple-bus" listed as the
compatible string so uart is populated as standard platform device.

>>> +		interrupt-parent = <&gic>;
>>> +		ranges = <0x00000000 0x18000000 0x00001000>;
>>
>> Does the 'apb' bus mean to cover all peripherals connected through APB?
>> If so, the size is only 0x1000 and that seems to be too small...
> 
> This is all that is currently needed.  I was planning on expanding it
> as I added more devices.

Sure.

I haven't checked the datahsheet but based on the layout (which seems
quite similar to Cygnus), I assume the range for these devices should be
0x18000000 - 0x18ffffff? Just want to make sure there are no other
devices come before 0x18000000 so you don't need to change all these reg
offsets in the future.

> 
> Thanks,
> Jon
> 

Thanks,

Ray
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