Re: [PATCH 3/3] ACPI: Don't re-select SBS battery if it's already selected

[xavier.gnata@xxxxxxxxx]

On 14/03/2014 06:39, Lan Tianyu wrote:
> 2014-03-12 6:20 GMT+08:00 Matthew Garrett <matthew.garrett@xxxxxxxxxx>:
> > The existing SBS code explicitly sets the selected battery in the SBS
> > manager regardless of whether the battery in question is already selected.
> > This causes bus timeouts on Apple hardware. Check for this case and avoid
> > it.
> Hi Matthew:
>             This patch is to avoid a redundant battery select operation when
> the battery is selected. But the symptom "bus timeouts" is a bus transaction
> issue, right?  Will this happen during other SBS write/read operations? Do we
> need to increase the wait time of SMBUS transaction?

Well, the patch does the job and is needed on a macbook air.
What should we test to make it potentially better?


> > Signed-off-by: Matthew Garrett <matthew.garrett@xxxxxxxxxx>
> > ---
> >   drivers/acpi/sbs.c | 18 +++++++++++++-----
> >   1 file changed, 13 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/acpi/sbs.c b/drivers/acpi/sbs.c
> > index dbd4849..c386505 100644
> > --- a/drivers/acpi/sbs.c
> > +++ b/drivers/acpi/sbs.c
> > @@ -470,17 +470,25 @@ static struct device_attribute alarm_attr = {
> >   static int acpi_battery_read(struct acpi_battery *battery)
> >   {
> >          int result = 0, saved_present = battery->present;
> > -       u16 state;
> > +       u16 state, selected, desired;
> >
> >          if (battery->sbs->manager_present) {
> >                  result = acpi_smbus_read(battery->sbs->hc, SMBUS_READ_WORD,
> >                                  ACPI_SBS_MANAGER, 0x01, (u8 *)&state);
> >                  if (!result)
> >                          battery->present = state & (1 << battery->id);
> > -               state &= 0x0fff;
> > -               state |= 1 << (battery->id + 12);
> > -               acpi_smbus_write(battery->sbs->hc, SMBUS_WRITE_WORD,
> > -                                 ACPI_SBS_MANAGER, 0x01, (u8 *)&state, 2);
> > +               /*
> > +                * Don't switch battery if the correct one is already selected
> > +                */
> > +               selected = state & 0xf000;
> > +               desired = 1 << (battery->id + 12);
> > +               if (selected != desired) {
> > +                       state &= 0x0fff;
> > +                       state |= desired;
> > +                       acpi_smbus_write(battery->sbs->hc, SMBUS_WRITE_WORD,
> > +                                        ACPI_SBS_MANAGER, 0x01,
> > +                                        (u8 *)&state, 2);
> > +               }
> >          } else if (battery->id == 0)
> >                  battery->present = 1;
> >          if (result || !battery->present)
> > --
> > 1.8.5.3
> >
> > --
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