On Tue, 2021-11-23 at 07:56 -0800, Guenter Roeck wrote:
> On Tue, Nov 23, 2021 at 03:07:04PM +0100, Iwona Winiarska wrote:
> > Add peci-dimmtemp driver for Temperature Sensor on DIMM readings that
> > are accessible via the processor PECI interface.
> >
> > The main use case for the driver (and PECI interface) is out-of-band
> > management, where we're able to obtain thermal readings from an external
> > entity connected with PECI, e.g. BMC on server platforms.
> >
> > Co-developed-by: Jae Hyun Yoo <jae.hyun.yoo@xxxxxxxxxxxxxxx>
> > Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@xxxxxxxxxxxxxxx>
> > Signed-off-by: Iwona Winiarska <iwona.winiarska@xxxxxxxxx>
> > Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>
> > ---
>
> [ ... ]
>
> > +static int check_populated_dimms(struct peci_dimmtemp *priv)
> > +{
> > + int chan_rank_max = priv->gen_info->chan_rank_max;
> > + int dimm_idx_max = priv->gen_info->dimm_idx_max;
> > + u32 chan_rank_empty = 0;
> > + u64 dimm_mask = 0;
> > + int chan_rank, dimm_idx, ret;
> > + u32 pcs;
> > +
> > + BUILD_BUG_ON(BITS_PER_TYPE(chan_rank_empty) < CHAN_RANK_MAX);
> > + BUILD_BUG_ON(BITS_PER_TYPE(dimm_mask) < DIMM_NUMS_MAX);
> > + if (chan_rank_max * dimm_idx_max > DIMM_NUMS_MAX) {
> > + WARN_ONCE(1, "Unsupported number of DIMMs - chan_rank_max:
> > %d, dimm_idx_max: %d",
> > + chan_rank_max, dimm_idx_max);
> > + return -EINVAL;
> > + }
> > +
> > + for (chan_rank = 0; chan_rank < chan_rank_max; chan_rank++) {
> > + ret = peci_pcs_read(priv->peci_dev, PECI_PCS_DDR_DIMM_TEMP,
> > chan_rank, &pcs);
> > + if (ret) {
> > + /*
> > + * Overall, we expect either success or -EINVAL in
> > + * order to determine whether DIMM is populated or
> > not.
> > + * For anything else we fall back to deferring the
> > + * detection to be performed at a later point in
> > time.
> > + */
> > + if (ret == -EINVAL) {
> > + chan_rank_empty |= BIT(chan_rank);
> > + continue;
> > + }
> > +
> > + return -EAGAIN;
> > + }
> > +
> > + for (dimm_idx = 0; dimm_idx < dimm_idx_max; dimm_idx++)
> > + if (__dimm_temp(pcs, dimm_idx))
> > + dimm_mask |= BIT(chan_rank * dimm_idx_max +
> > dimm_idx);
> > + }
> > +
> > + /*
> > + * If we got all -EINVALs, it means that the CPU doesn't have any
> > + * DIMMs. Unfortunately, it may also happen at the very start of
> > + * host platform boot. Retrying a couple of times lets us make sure
> > + * that the state is persistent.
> > + */
> > + if (chan_rank_empty == GENMASK(chan_rank_max - 1, 0)) {
> > + if (priv->no_dimm_retry_count < NO_DIMM_RETRY_COUNT_MAX) {
> > + priv->no_dimm_retry_count++;
> > +
> > + return -EAGAIN;
> > + } else {
> > + return -ENODEV;
> > + }
>
> Static analyzers will complain "else after return is unnecessary".
I'll fix this in v5.
Thanks
-Iwona
>
> Guenter
