Re: [PATCH 3/3] amba: Properly handle device probe without IRQ domain

[Kefeng Wang]

On 2021/8/25 16:04, Saravana Kannan wrote:
> On Tue, Aug 24, 2021 at 9:05 PM Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> wrote:
> > On 2021/8/25 4:08, Saravana Kannan wrote:
> > > On Tue, Aug 24, 2021 at 1:05 PM Rob Herring <robh+dt@xxxxxxxxxx> 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@xxxxxxxxxx> 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@xxxxxxxxxxxxxxx>
> > > > > Cc: Rob Herring <robh+dt@xxxxxxxxxx>
> > > > > Cc: Frank Rowand <frowand.list@xxxxxxxxx>
> > > > > Reported-by: Ruizhe Lin <linruizhe@xxxxxxxxxx>
> > > > > Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> > > > > ---
> > > > >    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@xxxxxxxxxxxxxx/
> .