Hi Matthias,
On Tue, Mar 19, 2019 at 05:33:52PM -0700, Matthias Kaehlcke wrote:
> ...
> > @@ -95,6 +103,19 @@ static int rk3399_dmcfreq_target(struct device *dev, unsigned long *freq,
> >
> > mutex_lock(&dmcfreq->lock);
> >
> > + if (target_rate >= dmcfreq->odt_dis_freq)
> > + odt_enable = true;
> > +
> > + /*
> > + * This makes a SMC call to the TF-A to set the DDR PD (power-down)
> > + * timings and to enable or disable the ODT (on-die termination)
> > + * resistors.
> > + */
> > + arm_smccc_smc(ROCKCHIP_SIP_DRAM_FREQ, dmcfreq->odt_pd_arg0,
> > + dmcfreq->odt_pd_arg1,
> > + ROCKCHIP_SIP_CONFIG_DRAM_SET_ODT_PD,
> > + odt_enable, 0, 0, 0, &res);
>
> Is it necessary/desirable to make this call for every frequency
> change? IIUC it should be only needed when odt_enable changes and the
> driver could track the state. If the DDR frequency doesn't change too
> often and the overhead of the call is small it shouldn't be really
> important though.
>
I will test your solution first to make sure there is no regression to
run that call for frequency change only.
Also, the call takes around 300us.
> > ...
> > @@ -334,6 +357,34 @@ static int rk3399_dmcfreq_probe(struct platform_device *pdev)
> > return ret;
> > }
> >
> > + /* Try to find the optional reference to the pmu syscon */
> > + node = of_parse_phandle(np, "rockchip,pmu", 0);
> > + if (node) {
>
> The 'optional' part doesn't seem to be accurate: according to the
> binding (https://lore.kernel.org/patchwork/patch/1052322/) the
> property is required and the code below assumes that data->regmap_pmu
> is set.
>
Indeed.
> > + data->regmap_pmu = syscon_node_to_regmap(node);
> > + if (IS_ERR(data->regmap_pmu))
> > + return PTR_ERR(data->regmap_pmu);
> > + }
> > +
> > + /* Get DDR type */
>
> nit: the comment doesn't add much value, thanks to good variable
> naming this is evident from the code.
>
> > + regmap_read(data->regmap_pmu, RK3399_PMUGRF_OS_REG2, &val);
> > + ddr_type = (val >> RK3399_PMUGRF_DDRTYPE_SHIFT) &
> > + RK3399_PMUGRF_DDRTYPE_MASK;
> > +
> > + /* Get the odt_dis_freq parameter in function of the DDR type */
>
> nit: ditto
>
> (if you prefer to keep these comments I'm not opposed to keeping them,
> but I don't think they are needed)
>
I will remove all the comments in the v3.
> Cheers
>
> Matthias
>
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Regards,
Gaël
