linux-kernel - Re: [PATCH 2/2] arm64: dts: ti: am642-evm: Add overlay for NAND expansion card

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Date:   Fri, 22 Sep 2023 12:03:23 +0300
From:   Roger Quadros <rogerq@...nel.org>
To:     Andrew Davis <afd@...com>, Nishanth Menon <nm@...com>,
        Tony Lindgren <tony@...mide.com>,
        Rob Herring <robh+dt@...nel.org>, david@...son.dropbear.id.au
Cc:     vigneshr@...com, krzysztof.kozlowski+dt@...aro.org,
        conor+dt@...nel.org, srk@...com,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Siddharth Vadapalli <s-vadapalli@...com>
Subject: Re: [PATCH 2/2] arm64: dts: ti: am642-evm: Add overlay for NAND
 expansion card



On 21/09/2023 20:23, Andrew Davis wrote:
> On 9/21/23 6:37 AM, Roger Quadros wrote:
>> On 20/09/2023 20:06, Andrew Davis wrote:
>>> On 9/20/23 11:44 AM, Nishanth Menon wrote:
>>>> On 18:18-20230920, Roger Quadros wrote:
>>>>>
>>>>>
>>>>> On 20/09/2023 16:58, Nishanth Menon wrote:
>>>>>> On 16:34-20230920, Roger Quadros wrote:
>>>>>>> The NAND expansion card plugs in over the HSE (High Speed Expansion)
>>>>>>> connector. Add support for it.
>>>>>>>
>>>>>>> Signed-off-by: Roger Quadros <rogerq@...nel.org>
>>>>>>> ---
>>>>>>>    arch/arm64/boot/dts/ti/Makefile               |   1 +
>>>>>>>    arch/arm64/boot/dts/ti/k3-am642-evm-nand.dtso | 140 ++++++++++++++++++
>>>>>>>    2 files changed, 141 insertions(+)
>>>>>>>    create mode 100644 arch/arm64/boot/dts/ti/k3-am642-evm-nand.dtso
>>>>>>>
>>>>>>> diff --git a/arch/arm64/boot/dts/ti/Makefile b/arch/arm64/boot/dts/ti/Makefile
>>>>>>> index 06d6f264f292..ece74085a6be 100644
>>>>>>> --- a/arch/arm64/boot/dts/ti/Makefile
>>>>>>> +++ b/arch/arm64/boot/dts/ti/Makefile
>>>>>>> @@ -29,6 +29,7 @@ dtb-$(CONFIG_ARCH_K3) += k3-am62p5-sk.dtb
>>>>>>>      # Boards with AM64x SoC
>>>>>>>    dtb-$(CONFIG_ARCH_K3) += k3-am642-evm.dtb
>>>>>>> +dtb-$(CONFIG_ARCH_K3) += k3-am642-evm-nand.dtbo
>>>>>>>    dtb-$(CONFIG_ARCH_K3) += k3-am642-phyboard-electra-rdk.dtb
>>>>>>>    dtb-$(CONFIG_ARCH_K3) += k3-am642-sk.dtb
>>>>>>>    dtb-$(CONFIG_ARCH_K3) += k3-am642-tqma64xxl-mbax4xxl.dtb
>>>>>>
>>>>>> Also see https://lore.kernel.org/all/20230911165610.GA1362932-robh@kernel.org/
>>>>>>
>>>>>> you may not get the dtbo installed when doing make dtbs_install
>>>>>>
>>>>>> [...]
>>>>>>
>>>>>
>>>>> $ v8make dtbs_install INSTALL_DTBS_PATH=/tmp
>>>>>     INSTALL /tmp/ti/k3-am625-beagleplay.dtb
>>>>>     INSTALL /tmp/ti/k3-am625-phyboard-lyra-rdk.dtb
>>>>>     INSTALL /tmp/ti/k3-am625-sk.dtb
>>>>>     INSTALL /tmp/ti/k3-am625-verdin-nonwifi-dahlia.dtb
>>>>>     INSTALL /tmp/ti/k3-am625-verdin-nonwifi-dev.dtb
>>>>>     INSTALL /tmp/ti/k3-am625-verdin-nonwifi-yavia.dtb
>>>>>     INSTALL /tmp/ti/k3-am625-verdin-wifi-dahlia.dtb
>>>>>     INSTALL /tmp/ti/k3-am625-verdin-wifi-dev.dtb
>>>>>     INSTALL /tmp/ti/k3-am625-verdin-wifi-yavia.dtb
>>>>>     INSTALL /tmp/ti/k3-am62-lp-sk.dtb
>>>>>     INSTALL /tmp/ti/k3-am62x-sk-hdmi-audio.dtbo
>>>>>     INSTALL /tmp/ti/k3-am62a7-sk.dtb
>>>>>     INSTALL /tmp/ti/k3-am62p5-sk.dtb
>>>>>     INSTALL /tmp/ti/k3-am642-evm.dtb
>>>>>     INSTALL /tmp/ti/k3-am642-evm-nand.dtbo
>>>>> ^^^^
>>>>>     INSTALL /tmp/ti/k3-am642-phyboard-electra-rdk.dtb
>>>>>     INSTALL /tmp/ti/k3-am642-sk.dtb
>>>>>
>>>>>
>>>>> What did I miss?
>>>>
>>>> I missed it, actually. See Rob's comment:
>>>> https://lore.kernel.org/all/CAL_Jsq+GR3hP6hFvFn2z5aXvSXnh9butD3aKZ-y_XJgx0_YPTw@mail.gmail.com/
>>>>
>>>> Having orphan dtbo is apparently frowned upon
>>>>
>>>
>>> And if you apply these overlays to the base DTB then it gets
>>> symbols added automatically, no need for your patch [1/2] here.
>>>
>>
>> Is this OK?
>>
>>     k3-am642-evm-nand-dtbs := k3-am642-evm.dtb k3-am642-evm-nand.dtbo
>>     dtb-$(CONFIG_ARCH_K3) += k3-am642-evm-nand.dtb
>>
>> So patch 1 is not required in this case but we have an
>> extra dtb file which is not really required.
>>
> 
> While I agree we will end up with several pre-overlayed DTB files
> that are arguably not required as they could be later built/applied,
> until we find a better way to check at build time these overlays
> need applied to something as a test.
> 
>> I have 2 more issues to point out
>>
>> 1)
>> With existing examples e.g. J7200 EVM
>> wouldn't  k3-j7200-evm.dtb include the k3-j7200-evm-quad-port-eth-exp.dtbo?
>> Is this what we really want?
>>
>> likewise for k3-j721e-evm.dtb and k3-am654-gp-evm.dtb
>>
> 
> Yes, that is the idea, the base-board.dtb is just the raw main board, but
> the "EVM" when you buy it comes with the quad-port daughtercard attached.
> That is what we consider the "EVM" and the DTB names match that.
> 
>> 2)
>> Another issue (unrelated to this change) is the below warning:
>>
>>     arch/arm64/boot/dts/ti/k3-am642-evm-nand.dtso:65.8-140.3: Warning (avoid_default_addr_size): /fragment@..._overlay__: Relying on default #address-cells value
>>     arch/arm64/boot/dts/ti/k3-am642-evm-nand.dtso:65.8-140.3: Warning (avoid_default_addr_size): /fragment@..._overlay__: Relying on default #size-cells value
>>
>> This is because we use the 'ranges' property in the gpmc0 node
>> and the compiler doesn't know the #address/size-cells of the
>> parent node.
>>
>> Is there a trick to specify it in the dtso file?
>>
> 
> Hmm, seems like a tricky one. Do you really need to do the ranges here?
> Could you use the default `ranges;` for gpmc0? Then do the range translation
> down inside the nand node to keep the partition addresses sane.

GPMC has separate address spaces per chip select. 

>From Documentation/devicetree/bindings/memory-controllers/ti,gpmc.yaml
  ranges:
    minItems: 1
    description: |
      Must be set up to reflect the memory layout with four
      integer values for each chip-select line in use,
      <cs-number> 0 <physical address of mapping> <size>

The ranges location in the device tree overlay is correct. The overlay is
meaningless without the base tree.

The correct solution would be to fix dtc so it doesn't print this warning
for DT overlays.

i.e.

diff --git a/scripts/dtc/checks.c b/scripts/dtc/checks.c
index 9f31d2607182..dcb0a6f6f3fb 100644
--- a/scripts/dtc/checks.c
+++ b/scripts/dtc/checks.c
@@ -1203,6 +1203,9 @@ static void check_avoid_default_addr_size(struct check *c, struct dt_info *dti,
        if (!reg && !ranges)
                return;
 
+       if (streq(node->name, "__overlay__"))
+               return;
+
        if (node->parent->addr_cells == -1)
                FAIL(c, dti, node, "Relying on default #address-cells value");


-- 
cheers,
-roger