Re: [PATCH v4 05/11] ppc/pnv: Wire up pca9552 GPIO pins for PCIe hotplug power control

[Miles Glenn]

On Tue, 2023-11-21 at 19:36 +0100, Cédric Le Goater wrote:
> On 11/21/23 00:51, Glenn Miles wrote:
> > For power10-rainier, a pca9552 device is used for PCIe slot hotplug
> > power control by the Power Hypervisor code.  The code expects that
> > some time after it enables power to a PCIe slot by asserting one of
> > the pca9552 GPIO pins 0-4, it should see a "power good" signal
> > asserted
> > on one of pca9552 GPIO pins 5-9.
> 
> And this is what OPAL is not doing :
> 
>    
> https://github.com/open-power/skiboot/blob/master/platforms/astbmc/rainier.c#L65
> 
> Correct ?
> 

Ah, yes, I believe you are correct!

> > To simulate this behavior, we simply connect the GPIO outputs for
> > pins 0-4 to the GPIO inputs for pins 5-9.
> > 
> > Each PCIe slot is assigned 3 GPIO pins on the pca9552 device, for
> > control of up to 5 PCIe slots.  The per-slot signal names are:
> > 
> >     SLOTx_EN.......PHYP uses this as an output to enable
> >                    slot power.  We connect this to the
> >                    SLOTx_PG pin to simulate a PGOOD signal.
> >     SLOTx_PG.......PHYP uses this as in input to detect
> >                    PGOOD for the slot.  For our purposes
> >                    we just connect this to the SLOTx_EN
> >                    output.
> >     SLOTx_Control..PHYP uses this as an output to prevent
> >                    a race condition in the real hotplug
> >                    circuitry, but we can ignore this output
> >                    for simulation.
> > 
> > Signed-off-by: Glenn Miles <milesg@linux.vnet.ibm.com>
> > ---
> > 
> > Changes from previous version:
> >    - Code moved from pnv_chip_power10_realize to
> > pnv_rainier_i2c_init
> > 
> >   hw/ppc/pnv.c | 20 ++++++++++++++++++--
> >   1 file changed, 18 insertions(+), 2 deletions(-)
> > 
> > diff --git a/hw/ppc/pnv.c b/hw/ppc/pnv.c
> > index 9cefcd0fd6..80d25fc1bd 100644
> > --- a/hw/ppc/pnv.c
> > +++ b/hw/ppc/pnv.c
> > @@ -1898,8 +1898,24 @@ static void
> > pnv_rainier_i2c_init(PnvMachineState *pnv)
> >            * Add a PCA9552 I2C device for PCIe hotplug control
> >            * to engine 2, bus 1, address 0x63
> >            */
> > -        i2c_slave_create_simple(chip10->i2c[2].busses[1],
> > -                                "pca9552", 0x63);
> > +        I2CSlave *hotplug = i2c_slave_create_simple(chip10-
> > >i2c[2].busses[1],
> > +                                                "pca9552", 0x63);
> 
> hotplug ? why not dev simply ?
> 
> 
> Thanks,
> 
> C.
> 
> 
Sure, dev is fine.  I'll change it.

Thanks,

Glenn

> 
> > +
> > +        /*
> > +         * Connect PCA9552 GPIO pins 0-4 (SLOTx_EN) outputs to
> > GPIO pins 5-9
> > +         * (SLOTx_PG) inputs in order to fake the pgood state of
> > PCIe slots
> > +         * after hypervisor code sets a SLOTx_EN pin high.
> > +         */
> > +        qdev_connect_gpio_out(DEVICE(hotplug), 0,
> > +                              qdev_get_gpio_in(DEVICE(hotplug),
> > 5));
> > +        qdev_connect_gpio_out(DEVICE(hotplug), 1,
> > +                              qdev_get_gpio_in(DEVICE(hotplug),
> > 6));
> > +        qdev_connect_gpio_out(DEVICE(hotplug), 2,
> > +                              qdev_get_gpio_in(DEVICE(hotplug),
> > 7));
> > +        qdev_connect_gpio_out(DEVICE(hotplug), 3,
> > +                              qdev_get_gpio_in(DEVICE(hotplug),
> > 8));
> > +        qdev_connect_gpio_out(DEVICE(hotplug), 4,
> > +                              qdev_get_gpio_in(DEVICE(hotplug),
> > 9));
> >       }
> >   }
> >