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Subject: Re: [PATCH 3/3] amba: Properly handle device probe without IRQ domain
To:     Saravana Kannan <saravanak@google.com>
CC:     Rob Herring <robh+dt@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Frank Rowand <frowand.list@gmail.com>,
        <devicetree@vger.kernel.org>, Russell King <linux@armlinux.org.uk>,
        "Linus Walleij" <linus.walleij@linaro.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        Ruizhe Lin <linruizhe@huawei.com>
References: <20210816074619.177383-1-wangkefeng.wang@huawei.com>
 <20210816074619.177383-4-wangkefeng.wang@huawei.com>
 <CAL_JsqLBddXVeP-t++wqPNp=xYF7tvEcnCbjFnK9CUBLK2+9JA@mail.gmail.com>
 <CAGETcx8SY14rcd7g=Gdwmw7sUMb=jdEV+ffuNpg6btDoL1jmWw@mail.gmail.com>
 <ee649111-dc07-d6db-8872-dcb692802236@huawei.com>
 <CAGETcx9drOdE_vfn-nhDZM9MbgxGxYJN6ydiAVxo_Ltqve9eTg@mail.gmail.com>
From:   Kefeng Wang <wangkefeng.wang@huawei.com>
Message-ID: <eb7f0980-f735-dd3b-fd66-63c8cd69cc58@huawei.com>
Date:   Wed, 25 Aug 2021 16:39:48 +0800
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On 2021/8/25 16:04, Saravana Kannan wrote:
> On Tue, Aug 24, 2021 at 9:05 PM Kefeng Wang <wangkefeng.wang@huawei.com> wrote:
>>
>> On 2021/8/25 4:08, Saravana Kannan wrote:
>>> On Tue, Aug 24, 2021 at 1:05 PM Rob Herring <robh+dt@kernel.org> wrote:
>>>> +Saravana
>>>>
>>>> Saravana mentioned to me there may be some issues with this one...
>>>>
>>>>
>>>> On Mon, Aug 16, 2021 at 2:43 AM Kefeng Wang <wangkefeng.wang@huawei.com> wrote:
>>>>> of_amba_device_create() uses irq_of_parse_and_map() to translate
>>>>> a DT interrupt specification into a Linux virtual interrupt number.
>>>>>
>>>>> But it doesn't properly handle the case where the interrupt controller
>>>>> is not yet available, eg, when pl011 interrupt is connected to MBIGEN
>>>>> interrupt controller, because the mbigen initialization is too late,
>>>>> which will lead to no IRQ due to no IRQ domain found, log is shown below,
>>>>>     "irq: no irq domain found for uart0 !"
>>>>>
>>>>> use of_irq_get() to return -EPROBE_DEFER as above, and in the function
>>>>> amba_device_try_add()/amba_device_add(), it will properly handle in such
>>>>> case, also return 0 in other fail cases to be consistent as before.
>>>>>
>>>>> Cc: Russell King <linux@armlinux.org.uk>
>>>>> Cc: Rob Herring <robh+dt@kernel.org>
>>>>> Cc: Frank Rowand <frowand.list@gmail.com>
>>>>> Reported-by: Ruizhe Lin <linruizhe@huawei.com>
>>>>> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
>>>>> ---
>>>>>    drivers/amba/bus.c    | 27 +++++++++++++++++++++++++++
>>>>>    drivers/of/platform.c |  6 +-----
>>>>>    2 files changed, 28 insertions(+), 5 deletions(-)
>>>>>
>>>>> diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
>>>>> index 36f2f42c8014..720aa6cdd402 100644
>>>>> --- a/drivers/amba/bus.c
>>>>> +++ b/drivers/amba/bus.c
>>>>> @@ -19,6 +19,7 @@
>>>>>    #include <linux/clk/clk-conf.h>
>>>>>    #include <linux/platform_device.h>
>>>>>    #include <linux/reset.h>
>>>>> +#include <linux/of_irq.h>
>>>>>
>>>>>    #include <asm/irq.h>
>>>>>
>>>>> @@ -371,12 +372,38 @@ static void amba_device_release(struct device *dev)
>>>>>           kfree(d);
>>>>>    }
>>>>>
>>>>> +static int of_amba_device_decode_irq(struct amba_device *dev)
>>>>> +{
>>>>> +       struct device_node *node = dev->dev.of_node;
>>>>> +       int i, irq = 0;
>>>>> +
>>>>> +       if (IS_ENABLED(CONFIG_OF_IRQ) && node) {
>>>>> +               /* Decode the IRQs and address ranges */
>>>>> +               for (i = 0; i < AMBA_NR_IRQS; i++) {
>>>>> +                       irq = of_irq_get(node, i);
>>>>> +                       if (irq < 0) {
>>>>> +                               if (irq == -EPROBE_DEFER)
>>>>> +                                       return irq;
>>>>> +                               irq = 0;
>>>>> +                       }
>>>>> +
>>>>> +                       dev->irq[i] = irq;
>>>>> +               }
>>>>> +       }
>>>>> +
>>>>> +       return 0;
>>>>> +}
>>>>> +
>>>>>    static int amba_device_try_add(struct amba_device *dev, struct resource *parent)
>>>>>    {
>>>>>           u32 size;
>>>>>           void __iomem *tmp;
>>>>>           int i, ret;
>>>>>
>>>>> +       ret = of_amba_device_decode_irq(dev);
>>>>> +       if (ret)
>>>>> +               goto err_out;
>>>>> +
>>> Similar to other resources the AMBA bus "gets" for the device, I think
>>> this should be moved into amba_probe() and not here. There's no reason
>>> to delay the addition of the device (and loading its module) because
>>> the IRQ isn't ready yet.
>> The following code in the amba_device_try_add() will be called, it uses irq[0]
>> and irq[1], so I put of_amba_device_decode_irq() into amba_device_try_add().
>>
>> 470         if (dev->irq[0])
>> 471                 ret = device_create_file(&dev->dev, &dev_attr_irq0);
>> 472         if (ret == 0 && dev->irq[1])
>> 473                 ret = device_create_file(&dev->dev, &dev_attr_irq1);
>> 474         if (ret == 0)
>> 475                 return ret;
>>
>> of_amba_device_decode_irq() in amba_device_try_add() won't lead to issue,
>> only delay the device add, right?
> But delaying the device add is the issue. For example, adding a device
> could trigger the loading of the corresponding module using uevents.
> But now this change would delay that step. That can have other
> unintended consequences -- slowing down boot, what if the driver was
> working fine without the IRQ, etc.
>
>> If make it into amba_probe(), the above code should be moved too, could we
>> make a new patch to move both of them, or don't move them?
> I'd say move them both. If Russell hasn't already picked this up, then
> I'd say redo your Patch 3/3.


Sure，I will update it and resend.

>
> Btw, I've been working on [1] cleaning up the one-off deferred probe
> solution that we have for amba devices. That causes a bunch of other
> headaches. Your patch 3/3 takes us further in the wrong direction by
> adding more reasons for delaying the addition of the device.
Thanks for your explanation.
> -Saravana
>
> [1] - https://lore.kernel.org/lkml/CAGETcx8b228nDUho3cX9AAQ-pXOfZTMv8cj2vhdx9yc_pk8q+A@mail.gmail.com/
> .
>