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SubjectRe: [v4 5/5] hwmon: Add Aspeed ast2600 TACH support
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On 11/28/22 23:08, Billy Tsai wrote:
> On 2022/11/23, 11:45 PM, "Guenter Roeck" <groeck7@gmail.com on behalf of linux@roeck-us.net> wrote:
>
> On 11/22/22 22:16, Billy Tsai wrote:
> > > +The driver provides the following sensor accesses in sysfs:
> > > +=============== ======= =====================================================
> > > +fanX_input ro provide current fan rotation value in RPM as reported
> > > + by the fan to the device.
> > > +fanX_div rw Fan divisor: Supported value are power of 4 (1, 4, 16
> > > + 64, ... 4194304)
>
> > The code doesn't support 1.
>
> The code can support 1.
>
Sorry, leftover from when I misread the code and thought it didn't.
>
> > The existence of a status register makes me wonder what is in there.
> > Does the controller report any errors ? If so, it might be worthwile
> > adding attribute(s) for it.
>
> > > + if (ret)
> > > + return ret;
> > > +
> > > + if (!(val & TACH_ASPEED_FULL_MEASUREMENT))
> > > + return 0;
> > > + rpm = aspeed_tach_val_to_rpm(priv, fan_tach_ch,
> > > + val & TACH_ASPEED_VALUE_MASK);
> > > +
> > > + return rpm;
>
> The status register is the TACH_ASPEED_FULL_MEASUREMENT which is used to indicate that
> the controller doesn't detect the change in tach pin for a long time.
>
> > > +static void aspeed_create_fan_tach_channel(struct aspeed_tach_data *priv,
> > > + u32 tach_ch)
> > > +{
> > > + priv->tach_present[tach_ch] = true;
> > > + priv->tach_channel[tach_ch].limited_inverse = 0;
> > > + regmap_write_bits(priv->regmap, TACH_ASPEED_CTRL(tach_ch),
> > > + TACH_ASPEED_INVERS_LIMIT,
> > > + priv->tach_channel[tach_ch].limited_inverse ?
> > > + TACH_ASPEED_INVERS_LIMIT :
> > > + 0);
> > > +
> > What is the purpose of the above code ? limited_inverse is always 0.
>
> > > + priv->tach_channel[tach_ch].tach_debounce = DEBOUNCE_3_CLK;
> > > + regmap_write_bits(priv->regmap, TACH_ASPEED_CTRL(tach_ch),
> > > + TACH_ASPEED_DEBOUNCE_MASK,
> > > + priv->tach_channel[tach_ch].tach_debounce
> > > + << TACH_ASPEED_DEBOUNCE_BIT);
> > > +
> > > + priv->tach_channel[tach_ch].tach_edge = F2F_EDGES;
> > > + regmap_write_bits(priv->regmap, TACH_ASPEED_CTRL(tach_ch),
> > > + TACH_ASPEED_IO_EDGE_MASK,
> > > + priv->tach_channel[tach_ch].tach_edge
> > > + << TACH_ASPEED_IO_EDGE_BIT);
> > > +
>
> > limited_inverse, tach_debounce, and tach_edge are constants.
> > There is no need to keep constants as per-channel variables.
>
> > > + priv->tach_channel[tach_ch].divisor = DEFAULT_TACH_DIV;
> > > + regmap_write_bits(priv->regmap, TACH_ASPEED_CTRL(tach_ch),
> > > + TACH_ASPEED_CLK_DIV_T_MASK,
> > > + DIV_TO_REG(priv->tach_channel[tach_ch].divisor)
> > > + << TACH_ASPEED_CLK_DIV_BIT);
> > > +
> > > + priv->tach_channel[tach_ch].threshold = 0;
> > > + regmap_write_bits(priv->regmap, TACH_ASPEED_CTRL(tach_ch),
> > > + TACH_ASPEED_THRESHOLD_MASK,
> > > + priv->tach_channel[tach_ch].threshold);
> > > +
>
> > The above applies to threshold as well.
>
> The above code is used to retain the adjustable feature of the controller.
> I will remove them until I add the dts property to support them.
>
> > > + }
> > > +
> > > + hwmon = devm_hwmon_device_register_with_info(dev, "aspeed_tach", priv,
> > > + &aspeed_tach_chip_info, NULL);
> > > + ret = PTR_ERR_OR_ZERO(hwmon);
> > > + if (ret)
> > > + return dev_err_probe(dev, ret,
> > > + "Failed to register hwmon device\n");
> > > + return 0;
>
> > Why not return the error ? Either it is an error or it isn't. If it is
> > not an error, dev_err_probe() is not appropriate. If it is, the error
> > should be returned. Either case, if this is on purpose, it needs an
> > explanation.
>
> I have return the return value of the dev_err_probe. Did I miss someting?
>
No, me not having enough coffee when reviewing the code. Sorry for the noise.

Thanks,
Guenter

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