Re: [PATCH 2/2] OPP: fix dev_pm_opp_find_bw_*() when bandwidth table not initialized

[Neil Armstrong]

On 29/11/2024 09:41, Viresh Kumar wrote:
> On 28-11-24, 11:07, Neil Armstrong wrote:
> > If a driver calls dev_pm_opp_find_bw_ceil/floor() the retrieve bandwidth
> > from the OPP table but the bandwidth table was not created because the
> > interconnect properties were missing in the OPP consumer node, the
> > kernel will crash with:
> > Unable to handle kernel NULL pointer dereference at virtual address 0000000000000004
> > ...
> > pc : _read_bw+0x8/0x10
> > lr : _opp_table_find_key+0x9c/0x174
> > ...
> > Call trace:
> >    _read_bw+0x8/0x10 (P)
> >    _opp_table_find_key+0x9c/0x174 (L)
> >    _find_key+0x98/0x168
> >    dev_pm_opp_find_bw_ceil+0x50/0x88
> > ...
> >
> > In order to fix the crash, create an assert function to check
> > if the bandwidth table were created before trying to get a
> > bandwidth with _read_bw().
> >
> > Fixes: add1dc094a74 ("OPP: Use generic key finding helpers for bandwidth key")
> > Signed-off-by: Neil Armstrong <neil.armstrong@xxxxxxxxxx>
> > ---
> >   drivers/opp/core.c | 14 ++++++++++++--
> >   1 file changed, 12 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/opp/core.c b/drivers/opp/core.c
> > index 8692e8ce05b7c31a725ea3a7928f238c7a1d6f51..178780e294dad49c22d866930efb7b8b13ae2d61 100644
> > --- a/drivers/opp/core.c
> > +++ b/drivers/opp/core.c
> > @@ -114,6 +114,14 @@ static bool assert_clk_index(struct opp_table *opp_table, int index)
> >   	return opp_table->clk_count > index;
> >   }
> >   
> > +/*
> > + * Returns true if bandwidth table is large enough to contain the bandwidth index.
> > + */
> > +static bool assert_bandwidth_index(struct opp_table *opp_table, int index)
> > +{
> > +	return opp_table->path_count > index;
> > +}
> > +
> >   /**
> >    * dev_pm_opp_get_bw() - Gets the bandwidth corresponding to an opp
> >    * @opp:	opp for which bandwidth has to be returned for
> > @@ -913,7 +921,8 @@ struct dev_pm_opp *dev_pm_opp_find_bw_ceil(struct device *dev, unsigned int *bw,
> >   	unsigned long temp = *bw;
> >   	struct dev_pm_opp *opp;
> >   
> > -	opp = _find_key_ceil(dev, &temp, index, true, _read_bw, NULL);
> > +	opp = _find_key_ceil(dev, &temp, index, true, _read_bw,
> > +			     assert_bandwidth_index);
> >   	*bw = temp;
> >   	return opp;
> >   }
> > @@ -944,7 +953,8 @@ struct dev_pm_opp *dev_pm_opp_find_bw_floor(struct device *dev,
> >   	unsigned long temp = *bw;
> >   	struct dev_pm_opp *opp;
> >   
> > -	opp = _find_key_floor(dev, &temp, index, true, _read_bw, NULL);
> > +	opp = _find_key_floor(dev, &temp, index, true, _read_bw,
> > +			      assert_bandwidth_index);
> >   	*bw = temp;
> >   	return opp;
> >   }
>
> Applied. Thanks.

Wait, this needs the first patch to work, otherwise index is not passed to assert

Neil