Re: [PATCH 3/3] ARM: tegra: Add thermal reset (thermtrip) support to PMC

[Mikko Perttunen]

On 13/08/14 10:53, Thierry Reding wrote:
> * PGP Signed by an unknown key
>
> On Tue, Aug 05, 2014 at 11:13:00AM +0300, Mikko Perttunen wrote:
> > This adds a device tree controlled option to enable PMC-based
> > thermal reset in overheating situations. Thermtrip is supported on
> > Tegra114 and Tegra124. The thermal reset only works when the thermal
>
> The binding updates in patch 1/3 say that Tegra30 supports thermtrip as
> well.

Oops, forgot to update the commit message when adding Tegra30. 
Originally I wasn't sure if it was supported.

> > +void tegra_pmc_init_thermal_reset(struct device_node *np)
>
> It would be good for this to take a struct device * so that dev_*() can
> be used instead of pr_*().

Good point.

> > +{
> > +	u32 pmu_i2c_addr, i2c_ctrl_id, reg_addr, reg_data, pinmux;
> > +	bool pmu_16bit_ops;
> > +	u32 val, checksum;
>
> Nit: All other register accesses use "value" instead of "val" as the
> name for this variable.

Will fix.

> > +	const struct of_device_id *match = of_match_node(tegra_pmc_match, np);
> > +	const struct tegra_pmc_soc *data = match->data;
> > +
> > +	if (!data->has_thermal_reset)
> > +		return;
> > +
> > +	pmu_16bit_ops =
> > +		of_property_read_bool(np, "nvidia,thermtrip-pmu-16bit-ops");
>
> The formatting here (and below) is weird. I think this could be made
> more readable by shortening both property name and/or variable name:
>
> 	pmu_16bit = of_property_read_bool(np, "nvidia,thermtrip-pmu-16bit");
>
> And similarily for below.

Yeah, it's suboptimal. The problem will probably go away once I add the
thermtrip subnode.

> > +	if (of_property_read_u32(
> > +		np, "nvidia,thermtrip-pmu-i2c-addr", &pmu_i2c_addr))
> > +		goto disabled;
> > +	if (of_property_read_u32(
> > +		np, "nvidia,thermtrip-i2c-controller", &i2c_ctrl_id))
> > +		goto disabled;
> > +	if (of_property_read_u32(
> > +		np, "nvidia,thermtrip-reg-addr", &reg_addr))
> > +		goto disabled;
> > +	if (of_property_read_u32(
> > +		np, "nvidia,thermtrip-reg-data", &reg_data))
> > +		goto disabled;
> > +	if (of_property_read_u32(
> > +		np, "nvidia,thermtrip-pinmux", &pinmux))
> > +		pinmux = 0;
> > +
> > +	val = tegra_pmc_readl(PMC_SENSOR_CTRL);
> > +	val |= PMC_SENSOR_CTRL_SCRATCH_WRITE | PMC_SENSOR_CTRL_ENABLE_RST;
> > +	tegra_pmc_writel(val, PMC_SENSOR_CTRL);
>
> It's not immediately clear to me what this does (therefore it would be
> good to annotate it with a comment), but if this enables thermal
> tripping, shouldn't this be done *after* the registers below have been
> set up?

I'll move this.

> > +
> > +	val = (reg_data << PMC_SCRATCH54_DATA_SHIFT) |
> > +	      (reg_addr << PMC_SCRATCH54_ADDR_SHIFT);
> > +	tegra_pmc_writel(val, PMC_SCRATCH54);
> > +
> > +	val = 0;
> > +	val |= PMC_SCRATCH55_RESET_TEGRA;
> > +	val |= i2c_ctrl_id << PMC_SCRATCH55_CNTRL_ID_SHIFT;
> > +	val |= pinmux << PMC_SCRATCH55_PINMUX_SHIFT;
> > +	if (pmu_16bit_ops)
> > +		val |= PMC_SCRATCH55_16BITOP;
> > +	val |= pmu_i2c_addr << PMC_SCRATCH55_I2CSLV1_SHIFT;
> > +
> > +	checksum = reg_addr + reg_data + (val & 0xFF) + ((val >> 8) & 0xFF) +
> > +		((val >> 24) & 0xFF);
> > +	checksum &= 0xFF;
>
> I'd prefer lower-case hexadecimals. Also, what about bits 23:16? Are
> they not needed for the checksum? Again, a comment may help to explain
> this.

Yes, bits 23:16 will contain the checksum itself. I'll add a comment.

> > +	checksum = 0x100 - checksum;
> > +
> > +	val |= checksum << PMC_SCRATCH55_CHECKSUM_SHIFT;
> > +
> > +	tegra_pmc_writel(val, PMC_SCRATCH55);
> > +
> > +	pr_info("Tegra: PMC thermal reset enabled\n");
> > +
> > +	return;
> > +
> > +disabled:
> > +	pr_warn("Tegra: PMC thermal reset disabled\n");
>
> You're not giving anyone a clue about what went wrong, so when they see
> this warning they don't know what to do about it. Maybe all paths
> leading here should have a more specific warning message themselves.

I'll add better error messages. Adding the thermtrip node will make this 
look nicer as well, since I can just error out if the thermtrip node 
exists but a required property doesn't.

> Thierry
>
> * Unknown Key
> * 0x7F3EB3A1

Thanks,
Mikko
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