Re: [PATCH] soc: qcom: llcc: Fix dis_cap_alloc and retain_on_pc configuration

[Mukesh Ojha]

On 11/4/2023 1:03 AM, Bjorn Andersson wrote:
> On Fri, Nov 03, 2023 at 04:27:12PM +0530, Atul Dhudase wrote:
> > While programming dis_cap_alloc and retain_on_pc, set a bit
> > corresponding to a specific SCID without disturbing the
> > previously configured bits.
>
> As far as I can see, the only invocation of _qcom_llcc_cfg_program()
> comes from qcom_llcc_cfg_program(), which is only called once, from
> qcom_llcc_probe(), and here also seems to only be the single write to
> these two registers.

It does not look to be single write but the write is for each slice
in the same register which was overriding other slices values.

-Mukesh
> This implies that "the previously configured bits" would be some unknown
> configuration provided to us either from the bootloader or by reset of
> the hardware. As such this changes the value of the two registers from
> being known, to having 31 unknown bits.
>
>
> I'm not saying that the change is wrong, but you're altering the
> behavior of every platform except SDM845.
> As such, I want the commit message to provide an actual problem
> description, and mention the fact that you're changing the logic to
> retain the state prior to Linux.
>
> Regards,
> Bjorn
>
> > Fixes: c14e64b46944 ("soc: qcom: llcc: Support chipsets that can write to llcc")
> > Signed-off-by: Atul Dhudase <quic_adhudase@xxxxxxxxxxx>
> > ---
> >   drivers/soc/qcom/llcc-qcom.c | 8 ++++----
> >   1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/soc/qcom/llcc-qcom.c b/drivers/soc/qcom/llcc-qcom.c
> > index 674abd0d6700..509d972c1bd9 100644
> > --- a/drivers/soc/qcom/llcc-qcom.c
> > +++ b/drivers/soc/qcom/llcc-qcom.c
> > @@ -941,15 +941,15 @@ static int _qcom_llcc_cfg_program(const struct llcc_slice_config *config,
> >   		u32 disable_cap_alloc, retain_pc;
> >
> >   		disable_cap_alloc = config->dis_cap_alloc << config->slice_id;
> > -		ret = regmap_write(drv_data->bcast_regmap,
> > -				LLCC_TRP_SCID_DIS_CAP_ALLOC, disable_cap_alloc);
> > +		ret = regmap_update_bits(drv_data->bcast_regmap, LLCC_TRP_SCID_DIS_CAP_ALLOC,
> > +				BIT(config->slice_id), disable_cap_alloc);
> >   		if (ret)
> >   			return ret;
> >
> >   		if (drv_data->version < LLCC_VERSION_4_1_0_0) {
> >   			retain_pc = config->retain_on_pc << config->slice_id;
> > -			ret = regmap_write(drv_data->bcast_regmap,
> > -					LLCC_TRP_PCB_ACT, retain_pc);
> > +			ret = regmap_update_bits(drv_data->bcast_regmap, LLCC_TRP_PCB_ACT,
> > +					BIT(config->slice_id), retain_pc);
> >   			if (ret)
> >   				return ret;
> >   		}
> > --
> > 2.25.1