linux-kernel - Re: [PATCH] ARM: dts: BCM5301X: Fix pin controller node

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Message-ID: <a3680cea-e97f-c4a2-de21-a83a3d2c1b5d@broadcom.com>
Date:   Wed, 19 Aug 2020 14:14:20 -0700
From:   Ray Jui <ray.jui@...adcom.com>
To:     Florian Fainelli <f.fainelli@...il.com>,
        Christian Lamparter <chunkeey@...il.com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     Hauke Mehrtens <hauke@...ke-m.de>,
        Rafał Miłecki <zajec5@...il.com>,
        "maintainer:BROADCOM BCM5301X ARM ARCHITECTURE" 
        <bcm-kernel-feedback-list@...adcom.com>,
        Rob Herring <robh+dt@...nel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: dts: BCM5301X: Fix pin controller node



On 8/19/2020 1:49 PM, Florian Fainelli wrote:
> On 8/19/20 1:48 PM, Christian Lamparter wrote:
>> On 2020-08-19 06:23, Florian Fainelli wrote:
>>> The pin controller resources start at 0xc0 from the CRU base which is at
>>> 0x100 from th DMU base, for a final address of 0x1800_c1c0, whereas we
>>> are currently off by 0x100. The resource size of the CRU is also
>>> incorrect and should end at 0x248 bytes from 0x100 which is the start
>>> address. Finally, the compatibility strings defined for the
>>> pin-controller node should reflect the SoC being used.
>>>
>>> Fixes: 9994241ac97c ("ARM: dts: BCM5301X: Describe Northstar pins mux
>>> controller")
>>> Reported-by: Christian Lamparter <chunkeey@...il.com>
>>> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
>>> ---
>>> Christian, can you test this as a preliminary patch for your Cisco
>>> Meraki MR32 series? Thanks!
>>
>> Hm, it looks like this is more complicated than this. We should have
>> looked at pinctrl-ns.c's ns_pinctrl_probe() [0] before calling it.
>>
>> |    ns_pinctrl->regmap = syscon_node_to_regmap(of_get_parent(np));
>> |    if (IS_ERR(ns_pinctrl->regmap)) {
>> |        int err = PTR_ERR(ns_pinctrl->regmap);
>> |
>> |        dev_err(dev, "Failed to map pinctrl regs: %d\n", err);
>> |
>> |        return err;
>> |    }
>> |
>> |    if (of_property_read_u32(np, "offset", &ns_pinctrl->offset)) {
>> |        dev_err(dev, "Failed to get register offset\n");
>> |        return -ENOENT;
>> |    }
>>
>> So, the ns_pinctrl_probe() takes the address of the parent node (cru)
>> and then looks for a "offset" property to add to this (which is missing
>> in the bcm5301x.dtsi [1]).
>>
>> Thing is, for this to work, the parent-node should be a "simple-mfd" (so
>> a regmap is created for the reg), right? This would also mean that the
>> "reg" property in the pin-controller node is just cosmetic.
>>
>> I guess the reason why this sort-of-works for me is because I'm using
>> this MR32 with OpenWrt (Rafał Miłecki is probably using it too ;) ).
>>
>> (Note: We should not forget to update the binding-documentation as well!)
>>
>> BTW: I'll reply my findings for the i2c issue with the MR32 in the other
>> mail.
> 
> Rafal, has this driver ever worked to begin with? None of this should be
> necessary, we should just be using a simple platform device resource here.
> 

Florian, what if CDRU is a shared resource whose registers are accessed
and shared by multiple blocks (and therefore device drivers) within the
chip? Then accessing this shared CDRU resource through syscon makes sure
there's no race condition, isn't it?