Re: [PATCH 1/2] platform/x86: i2c-multi-instantiate: Add flag for passing fwnode

[Hans de Goede]

Hi,

On 4/26/20 7:59 PM, Andy Shevchenko wrote:
> On Sun, Apr 26, 2020 at 1:47 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
> > In some cases the driver for the i2c_client-s which i2c-multi-instantiate
> > instantiates may need access some fields / methods from to the ACPI fwnode
> > for which i2c_clients are being instantiated.
> >
> > An example of this are CPLM3218 ACPI device-s. These contain CPM0 and
> > CPM1 packages with various information (e.g. register init values) which
> > the driver needs.
> >
> > Passing the fwnode through the i2c_board_info struct also gives the
> > i2c-core access to it, and if we do not pass an IRQ then the i2c-core
> > will use the fwnode to get an IRQ, see i2c_acpi_get_irq().
>
> I'm wondering, can we rather do it in the same way like we do for
> GPIO/APIC case here.
> Introduce IRQ_RESOURCE_SHARED (or so) and
>
> case _SHARED:
>   irq = i2c_acpi_get_irq();
> ...
>
> ?

I think you are miss-understanding the problem. The problem is not that
we want to share the IRQ, the problem is that we want to pass the single
IRQ in the resources to only 1 of the instantiated I2C-clients. But if we
do not pass an IRQ (we leave it at 0) and we do pass the fwnode then
i2c-core-base.c will see that there is an ACPI-node attached to the
device and will call i2c_acpi_get_irq().

So the solution is definitely not calling i2c_acpi_get_irq() inside
i2c-multi-instantiate.c we want to avoid the i2c_acpi_get_irq(),
leaving the other 2 clients for the BSG1160 device without an IRQ
and thus avoiding the IRQ mismatch (it is a mismatch because the
drivers do not set the shared flag; and that is ok, we do not want
to share the IRQ, it is just for the accelerometer AFAIK).

Regards,

Hans


> > This is a problem when there is only an IRQ for 1 of the clients described
> > in the ACPI device we are instantiating clients for. If we unconditionally
> > pass the fwnode, then i2c_acpi_get_irq() will assign the same IRQ to all
> > clients instantiated, leading to kernel-oopses like this (BSG1160 device):
> >
> > [   27.340557] genirq: Flags mismatch irq 76. 00002001 (bmc150_magn_event) vs. 00000001 (bmc150_accel_event)
> > [   27.340567] Call Trace:
> > ...
> >
> > So we cannot simply always pass the fwnode. This commit adds a PASS_FWNODE
> > flag, which can be used to pass the fwnode in cases where we do not have
> > the IRQ problem and the driver for the instantiated client(s) needs access
> > to the fwnode.
> >
> > Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> > ---
> >   drivers/platform/x86/i2c-multi-instantiate.c | 6 ++++++
> >   1 file changed, 6 insertions(+)
> >
> > diff --git a/drivers/platform/x86/i2c-multi-instantiate.c b/drivers/platform/x86/i2c-multi-instantiate.c
> > index 6acc8457866e..dcafb1a29d17 100644
> > --- a/drivers/platform/x86/i2c-multi-instantiate.c
> > +++ b/drivers/platform/x86/i2c-multi-instantiate.c
> > @@ -20,6 +20,8 @@
> >   #define IRQ_RESOURCE_GPIO      1
> >   #define IRQ_RESOURCE_APIC      2
> >
> > +#define PASS_FWNODE            BIT(2)
> > +
> >   struct i2c_inst_data {
> >          const char *type;
> >          unsigned int flags;
> > @@ -93,6 +95,10 @@ static int i2c_multi_inst_probe(struct platform_device *pdev)
> >                  snprintf(name, sizeof(name), "%s-%s.%d", dev_name(dev),
> >                           inst_data[i].type, i);
> >                  board_info.dev_name = name;
> > +
> > +               if (inst_data[i].flags & PASS_FWNODE)
> > +                       board_info.fwnode = dev->fwnode;
> > +
> >                  switch (inst_data[i].flags & IRQ_RESOURCE_TYPE) {
> >                  case IRQ_RESOURCE_GPIO:
> >                          ret = acpi_dev_gpio_irq_get(adev, inst_data[i].irq_idx);
> > --
> > 2.26.0