Re: [PATCH v2 4/8] ppc/pnv: Fix PNV I2C invalid status after reset

[Miles Glenn <milesg@linux.vnet.ibm.com>]

On Mon, 2023-11-13 at 10:10 +0100, Cédric Le Goater wrote:
> On 11/10/23 20:49, Glenn Miles wrote:
> > The PNV I2C Controller was clearing the status register
> > after a reset without repopulating the "upper threshold
> > for I2C ports", "Command Complete" and the SCL/SDA input
> > level fields.
> > 
> > Fixed this for resets caused by a system reset as well
> > as from writing to the "Immediate Reset" register.
> > 
> > Signed-off-by: Glenn Miles <milesg@linux.vnet.ibm.com>
> > ---
> >   hw/ppc/pnv_i2c.c | 42 ++++++++++++++++++------------------------
> >   1 file changed, 18 insertions(+), 24 deletions(-)
> > 
> > diff --git a/hw/ppc/pnv_i2c.c b/hw/ppc/pnv_i2c.c
> > index b2c738da50..f80589157b 100644
> > --- a/hw/ppc/pnv_i2c.c
> > +++ b/hw/ppc/pnv_i2c.c
> > @@ -462,6 +462,23 @@ static uint64_t pnv_i2c_xscom_read(void
> > *opaque, hwaddr addr,
> >       return val;
> >   }
> >   
> > +static void pnv_i2c_reset(void *dev)
> > +{
> > +    PnvI2C *i2c = PNV_I2C(dev);
> > +
> > +    memset(i2c->regs, 0, sizeof(i2c->regs));
> > +
> > +    i2c->regs[I2C_STAT_REG] =
> > +        SETFIELD(I2C_STAT_UPPER_THRS, 0ull, i2c->num_busses - 1) |
> > +        I2C_STAT_CMD_COMP | I2C_STAT_SCL_INPUT_LEVEL |
> > +        I2C_STAT_SDA_INPUT_LEVEL;
> > +    i2c->regs[I2C_EXTD_STAT_REG] =
> > +        SETFIELD(I2C_EXTD_STAT_FIFO_SIZE, 0ull, PNV_I2C_FIFO_SIZE)
> > |
> > +        SETFIELD(I2C_EXTD_STAT_I2C_VERSION, 0ull, 23); /* last
> > version */
> > +
> > +    fifo8_reset(&i2c->fifo);
> > +}
> > +
> >   static void pnv_i2c_xscom_write(void *opaque, hwaddr addr,
> >                                   uint64_t val, unsigned size)
> >   {
> > @@ -499,16 +516,7 @@ static void pnv_i2c_xscom_write(void *opaque,
> > hwaddr addr,
> >           break;
> >   
> >       case I2C_RESET_I2C_REG:
> > -        i2c->regs[I2C_MODE_REG] = 0;
> > -        i2c->regs[I2C_CMD_REG] = 0;
> > -        i2c->regs[I2C_WATERMARK_REG] = 0;
> > -        i2c->regs[I2C_INTR_MASK_REG] = 0;
> > -        i2c->regs[I2C_INTR_COND_REG] = 0;
> > -        i2c->regs[I2C_INTR_RAW_COND_REG] = 0;
> > -        i2c->regs[I2C_STAT_REG] = 0;
> > -        i2c->regs[I2C_RESIDUAL_LEN_REG] = 0;
> > -        i2c->regs[I2C_EXTD_STAT_REG] &=
> > -            (I2C_EXTD_STAT_FIFO_SIZE | I2C_EXTD_STAT_I2C_VERSION);
> > +        pnv_i2c_reset(i2c);
> 
> or simply call device_cold_reset()
> 
> 
> Thanks,
> 
> C.
> 

The device_cold_reset() function performs a recursive reset, which
I believe performs a reset on the specified device as well as a reset
on all child devices.  For the case of doing an "immediate reset" of
the i2c controller, I think we just want to reset the i2c controller
and not any child devices, so I think I prefer leaving it how it is
if that is ok.

Thanks,

Glenn

> 
> 
> >           break;
> >   
> >       case I2C_RESET_ERRORS:
> > @@ -620,20 +628,6 @@ static int pnv_i2c_dt_xscom(PnvXScomInterface
> > *dev, void *fdt,
> >       return 0;
> >   }
> >   
> > -static void pnv_i2c_reset(void *dev)
> > -{
> > -    PnvI2C *i2c = PNV_I2C(dev);
> > -
> > -    memset(i2c->regs, 0, sizeof(i2c->regs));
> > -
> > -    i2c->regs[I2C_STAT_REG] = I2C_STAT_CMD_COMP;
> > -    i2c->regs[I2C_EXTD_STAT_REG] =
> > -        SETFIELD(I2C_EXTD_STAT_FIFO_SIZE, 0ull, PNV_I2C_FIFO_SIZE)
> > |
> > -        SETFIELD(I2C_EXTD_STAT_I2C_VERSION, 0ull, 23); /* last
> > version */
> > -
> > -    fifo8_reset(&i2c->fifo);
> > -}
> > -
> >   static void pnv_i2c_realize(DeviceState *dev, Error **errp)
> >   {
> >       PnvI2C *i2c = PNV_I2C(dev);