| Message ID | 1423608615-6575-1-git-send-email-tylerwhall@gmail.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | Eduardo Valentin |
| Headers | show |
Tyler, On Tue, Feb 10, 2015 at 05:50:15PM -0500, Tyler Hall wrote: > The current register being used to read the temperature returns a noisy value > that is prone to variance and occasional outliers. The value in the thermal > manager control and status register appears to have the same scale but much > less variability. > > Add a "marvell,armadaxp-filtered-thermal" config which is set up to read from > the Thermal Manager Control and Status Register at 0x184c4 rather than the > Thermal Sensor Status Register at 0x182b0. The only difference is the > temperature value shift. The original "marvell,armadaxp-thermal" is retained > for device tree compatibility. > > This also fixes Armada XP clearing the disable bit in the wrong register. Bit 0 > of the sensor register was being cleared but that bit is read-only. The disable > bit doesn't seem to have an effect on the temperature sensor value, however, so > this doesn't make a material difference. > > This problem was detected when running with the watchdog(8) daemon polling the > thermal value. In one instance I observed a single read of over 200 degrees C > which caused a spurious watchdog-initiated reboot. I have since observed > individual outliers of ~20 degrees C. With this change and the corresponding > device tree update, the temperature is much more stable. > > Signed-off-by: Tyler Hall <tylerwhall@gmail.com> > --- > > If there's a better way to handle this than a separate binding, I'm open to > suggestions. The fix seams reasonable. Although, it remains the question what is applicability to other Armada chips? Besides, shouldn't we simply use it by default? Also, do you plan to send updates in the DTS files? I would appreciate if you get a Review-by, from Ezequiel for instance, before we apply this. Ezequiel, any objections before I move forward with this one? BR, Eduardo Valentin > > My conclusions about these registers are based on experimental data. The > documentation is very sparse, but the Thermal Manager Control and Status > Register looks like the preferred register given the way it is laid out in the > public spec. > > I have the small corresponding patch to the dts which I can submit separately. > > Thanks > Tyler > > .../devicetree/bindings/thermal/armada-thermal.txt | 8 ++++++++ > drivers/thermal/armada_thermal.c | 13 +++++++++++++ > 2 files changed, 21 insertions(+) > > diff --git a/Documentation/devicetree/bindings/thermal/armada-thermal.txt b/Documentation/devicetree/bindings/thermal/armada-thermal.txt > index 4698e0e..0d6a3f1 100644 > --- a/Documentation/devicetree/bindings/thermal/armada-thermal.txt > +++ b/Documentation/devicetree/bindings/thermal/armada-thermal.txt > @@ -7,6 +7,14 @@ Required properties: > marvell,armada375-thermal > marvell,armada380-thermal > marvell,armadaxp-thermal > + marvell,armadaxp-filtered-thermal > + > + Note: "marvell,armadaxp-filtered-thermal" is adjusted to read > + the hardware-filtered value in the thermal manager > + control/status register rather than the raw sensor value in the > + thermal sensor status register. "marvell,armadaxp-thermal" > + remains for backward compatibility. The sensor reg address must > + also point to the appropriate register. > > - reg: Device's register space. > Two entries are expected, see the examples below. > diff --git a/drivers/thermal/armada_thermal.c b/drivers/thermal/armada_thermal.c > index c2556cf..d3c2ad3 100644 > --- a/drivers/thermal/armada_thermal.c > +++ b/drivers/thermal/armada_thermal.c > @@ -196,6 +196,15 @@ static const struct armada_thermal_data armadaxp_data = { > .coef_div = 13825, > }; > > +static const struct armada_thermal_data armadaxp_filt_data = { > + .init_sensor = armadaxp_init_sensor, > + .temp_shift = 1, > + .temp_mask = 0x1ff, > + .coef_b = 3153000000UL, > + .coef_m = 10000000UL, > + .coef_div = 13825, > +}; > + > static const struct armada_thermal_data armada370_data = { > .is_valid = armada_is_valid, > .init_sensor = armada370_init_sensor, > @@ -236,6 +245,10 @@ static const struct of_device_id armada_thermal_id_table[] = { > .data = &armadaxp_data, > }, > { > + .compatible = "marvell,armadaxp-filtered-thermal", > + .data = &armadaxp_filt_data, > + }, > + { > .compatible = "marvell,armada370-thermal", > .data = &armada370_data, > }, > -- > 2.3.0 >
Eduardo, On Tue, Feb 24, 2015 at 1:36 PM, Eduardo Valentin <edubezval@gmail.com> wrote: > The fix seams reasonable. Although, it remains the question what is > applicability to other Armada chips? Besides, shouldn't we simply use it > by default? Also, do you plan to send updates in the DTS files? As far as I can tell, Armada 370 is already using the equivalent of this register I'd like to use in Armada XP. I'm not sure about the other mvebu platforms. I couldn't just change the device tree for XP to instantiate the 370 sensor, however, as they have different initialization routines. Possibly Eziquiel can comment on the significance of the differences between armadaxp_init_sensor() and armada370_init_sensor(). I would like to change the default going forward, but I don't think it can be changed on platforms using an older DTB. I had planned to submit the dts change separately. It's not clear to me how that's supposed to be handled if they might go through different trees. Thanks, Tyler -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi Tyler, Eduardo, On 24/02/2015 20:56, Tyler Hall wrote: > Eduardo, > > On Tue, Feb 24, 2015 at 1:36 PM, Eduardo Valentin <edubezval@gmail.com> wrote: >> The fix seams reasonable. Although, it remains the question what is >> applicability to other Armada chips? Besides, shouldn't we simply use it >> by default? Also, do you plan to send updates in the DTS files? > > As far as I can tell, Armada 370 is already using the equivalent of > this register I'd like to use in Armada XP. I'm not sure about the > other mvebu platforms. I couldn't just change the device tree for XP > to instantiate the 370 sensor, however, as they have different > initialization routines. Possibly Eziquiel can comment on the > significance of the differences between armadaxp_init_sensor() and > armada370_init_sensor(). > > I would like to change the default going forward, but I don't think it > can be changed on platforms using an older DTB. Here you introduced a new kind of thermal sensor, at least from the point of view of the device tree. You used a new compatible string associated to a different register. By using it by default do you mean removing marvell,armadaxp-thermal and adding armadaxp-filtered-thermal instead ? Does that new thermal sensors only improve the stability or does it also modify the value? In the second case it will more or less break the user space expectation. > > I had planned to submit the dts change separately. It's not clear to > me how that's supposed to be handled if they might go through > different trees. For this, there is no problem be handled in a different tree. At the end we will need both the a new dts and a new driver to use it, so the fact that the dts or the driver patch is merged in mainline first is not important. Thanks, Gregory > > Thanks, > Tyler > -- > To unsubscribe from this list: send the line "unsubscribe devicetree" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >
Hi Tyler, On 10/02/2015 23:50, Tyler Hall wrote: > The current register being used to read the temperature returns a noisy value > that is prone to variance and occasional outliers. The value in the thermal > manager control and status register appears to have the same scale but much > less variability. > > Add a "marvell,armadaxp-filtered-thermal" config which is set up to read from > the Thermal Manager Control and Status Register at 0x184c4 rather than the > Thermal Sensor Status Register at 0x182b0. The only difference is the > temperature value shift. The original "marvell,armadaxp-thermal" is retained > for device tree compatibility. > > This also fixes Armada XP clearing the disable bit in the wrong register. Bit 0 > of the sensor register was being cleared but that bit is read-only. The disable > bit doesn't seem to have an effect on the temperature sensor value, however, so > this doesn't make a material difference. > > This problem was detected when running with the watchdog(8) daemon polling the > thermal value. In one instance I observed a single read of over 200 degrees C > which caused a spurious watchdog-initiated reboot. I have since observed > individual outliers of ~20 degrees C. With this change and the corresponding > device tree update, the temperature is much more stable. I tried your patch on a OpenBlocks AX3. Without it I observed a temperature of 47°C: # cat /sys/class/thermal/thermal_zone0/temp 47233 Whereas with your patch I got a temperature of 228°C! # cat /sys/class/thermal/thermal_zone0/temp 228065 It should have an error somewhere in the values used. > > Signed-off-by: Tyler Hall <tylerwhall@gmail.com> > --- > > If there's a better way to handle this than a separate binding, I'm open to > suggestions. Now that I thought more about it, I believe that it would make more sens extending the current binding by adding a new optional named register, indeed at the end we use the same sensor. The binding would become: thermal@182b0 { compatible = "marvell,armadaxp-thermal"; reg = <0x182b0 0x4 0x184d0 0x4 0x184c4 0x4>; reg-names = "sensor", "ctrl", "filt-sens"; status = "okay"; }; and then in the probe function we got something like res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "filt-sens"); if res { priv->sensor = devm_ioremap_resource(&pdev->dev, res); if (IS_ERR(priv->sensor)) return PTR_ERR(priv->sensor); } else { res = platform_get_resource(pdev, IORESOURCE_MEM, 0); priv->sensor = devm_ioremap_resource(&pdev->dev, res); if (IS_ERR(priv->sensor)) return PTR_ERR(priv->sensor); } My concern was that by introducing a new compatible string we don't prevent to have 2 thermal nodes for the same hardware. > > My conclusions about these registers are based on experimental data. The > documentation is very sparse, but the Thermal Manager Control and Status > Register looks like the preferred register given the way it is laid out in the > public spec. Ezequiel, as you worked on this do you know why we used the Thermal Sensor Status Register instead of the Thermal Manager Control and Status Register ? My first guess is that the giving the name of the registers the 1st one made more sens to use for a thermal sensor. Thanks, Gregory > > I have the small corresponding patch to the dts which I can submit separately. > > Thanks > Tyler > > .../devicetree/bindings/thermal/armada-thermal.txt | 8 ++++++++ > drivers/thermal/armada_thermal.c | 13 +++++++++++++ > 2 files changed, 21 insertions(+) > > diff --git a/Documentation/devicetree/bindings/thermal/armada-thermal.txt b/Documentation/devicetree/bindings/thermal/armada-thermal.txt > index 4698e0e..0d6a3f1 100644 > --- a/Documentation/devicetree/bindings/thermal/armada-thermal.txt > +++ b/Documentation/devicetree/bindings/thermal/armada-thermal.txt > @@ -7,6 +7,14 @@ Required properties: > marvell,armada375-thermal > marvell,armada380-thermal > marvell,armadaxp-thermal > + marvell,armadaxp-filtered-thermal > + > + Note: "marvell,armadaxp-filtered-thermal" is adjusted to read > + the hardware-filtered value in the thermal manager > + control/status register rather than the raw sensor value in the > + thermal sensor status register. "marvell,armadaxp-thermal" > + remains for backward compatibility. The sensor reg address must > + also point to the appropriate register. > > - reg: Device's register space. > Two entries are expected, see the examples below. > diff --git a/drivers/thermal/armada_thermal.c b/drivers/thermal/armada_thermal.c > index c2556cf..d3c2ad3 100644 > --- a/drivers/thermal/armada_thermal.c > +++ b/drivers/thermal/armada_thermal.c > @@ -196,6 +196,15 @@ static const struct armada_thermal_data armadaxp_data = { > .coef_div = 13825, > }; > > +static const struct armada_thermal_data armadaxp_filt_data = { > + .init_sensor = armadaxp_init_sensor, > + .temp_shift = 1, > + .temp_mask = 0x1ff, > + .coef_b = 3153000000UL, > + .coef_m = 10000000UL, > + .coef_div = 13825, > +}; > + > static const struct armada_thermal_data armada370_data = { > .is_valid = armada_is_valid, > .init_sensor = armada370_init_sensor, > @@ -236,6 +245,10 @@ static const struct of_device_id armada_thermal_id_table[] = { > .data = &armadaxp_data, > }, > { > + .compatible = "marvell,armadaxp-filtered-thermal", > + .data = &armadaxp_filt_data, > + }, > + { > .compatible = "marvell,armada370-thermal", > .data = &armada370_data, > }, >
On 02/25/2015 02:04 PM, Gregory CLEMENT wrote: >> >> My conclusions about these registers are based on experimental data. The >> documentation is very sparse, but the Thermal Manager Control and Status >> Register looks like the preferred register given the way it is laid out in the >> public spec. > > Ezequiel, > > as you worked on this do you know why we used the Thermal Sensor Status Register > instead of the Thermal Manager Control and Status Register ? > My first guess is that the giving the name of the registers the 1st one made > more sens to use for a thermal sensor. > Actually, we based this driver in the vendor bootloader. The specs weren't of much use back then.
Hi Ezequiel, On 25/02/2015 19:17, Ezequiel Garcia wrote: > On 02/25/2015 02:04 PM, Gregory CLEMENT wrote: >>> >>> My conclusions about these registers are based on experimental data. The >>> documentation is very sparse, but the Thermal Manager Control and Status >>> Register looks like the preferred register given the way it is laid out in the >>> public spec. >> >> Ezequiel, >> >> as you worked on this do you know why we used the Thermal Sensor Status Register >> instead of the Thermal Manager Control and Status Register ? >> My first guess is that the giving the name of the registers the 1st one made >> more sens to use for a thermal sensor. >> > > Actually, we based this driver in the vendor bootloader. The specs weren't > of much use back then. > Thanks for your prompt feedback. So we don't have much more information about the sensor. :( I will try to get information from Marvell. Tyler, In the meantime could you double check your values? The temperature on my board seemed broken on my board. If needed I can check on an other board. By the way on which board/product did you try it? Thanks, Gregory
On Wed, Feb 25, 2015 at 05:10:14PM +0100, Gregory CLEMENT wrote: > Hi Tyler, Eduardo, > > On 24/02/2015 20:56, Tyler Hall wrote: > > Eduardo, > > > > On Tue, Feb 24, 2015 at 1:36 PM, Eduardo Valentin <edubezval@gmail.com> wrote: > >> The fix seams reasonable. Although, it remains the question what is > >> applicability to other Armada chips? Besides, shouldn't we simply use it > >> by default? Also, do you plan to send updates in the DTS files? > > > > As far as I can tell, Armada 370 is already using the equivalent of > > this register I'd like to use in Armada XP. I'm not sure about the > > other mvebu platforms. I couldn't just change the device tree for XP > > to instantiate the 370 sensor, however, as they have different > > initialization routines. Possibly Eziquiel can comment on the > > significance of the differences between armadaxp_init_sensor() and > > armada370_init_sensor(). > > > > I would like to change the default going forward, but I don't think it > > can be changed on platforms using an older DTB. > > Here you introduced a new kind of thermal sensor, at least from the point > of view of the device tree. You used a new compatible string associated to > a different register. > > By using it by default do you mean removing marvell,armadaxp-thermal > and adding armadaxp-filtered-thermal instead ? > > Does that new thermal sensors only improve the stability or does it > also modify the value? > > In the second case it will more or less break the user space expectation. Yeah, I agree here. We need to understand if this is: (1) a fix of which register to use. In that case, the old dtbs are essentially wrong, and the driver would need to adapt, I would say. (2) a way to report better temperature extrapolations. then, this is essentially a new temp sensor, and we should have two separated compatible. in other words, just keep the patch the way it is. > > > > > I had planned to submit the dts change separately. It's not clear to > > me how that's supposed to be handled if they might go through > > different trees. > > For this, there is no problem be handled in a different tree. At the end > we will need both the a new dts and a new driver to use it, so the fact that > the dts or the driver patch is merged in mainline first is not important. > > Yes. Typically I ask to see the complete series, even if I am not taking the DTS changes. That is, you send a complete series, with changes in the kernel code and in the DTS, copying the required audience (from kernel side and from DT side). Once the changes are accepted, the patches will be picked by the correct tree maintainer. It is common that DTS changes go via the platform tree, to avoid conflicts though. In this way, we can have a look if the whole set of changes are going to make sense, instead of guessing if future DTS changes will be correct. > Thanks, > > Gregory > > > > > > Thanks, > > Tyler > > -- > > To unsubscribe from this list: send the line "unsubscribe devicetree" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > > -- > Gregory Clement, Free Electrons > Kernel, drivers, real-time and embedded Linux > development, consulting, training and support. > http://free-electrons.com
Hi Gregory, Eduardo, On Wed, Feb 25, 2015 at 05:10:14PM +0100, Gregory CLEMENT wrote: > By using it by default do you mean removing marvell,armadaxp-thermal > and adding armadaxp-filtered-thermal instead ? Yes, replacing it in device tree. For me, /sys/class/thermal/thermal_zone0/temp returns the same temperature but with less variability between samples. My intent was to switch the source of the data and not affect user space other than providing a more stable reading. > Tyler, > In the meantime could you double check your values? The temperature on my board > seemed broken on my board. If needed I can check on an other board. By the way > on which board/product did you try it? I'm on a custom board with the 4-core MV78460. In addition to my patch, this is new device tree entry. thermal@184c4 { compatible = "marvell,armadaxp-filtered-thermal"; reg = <0x184c4 0x4 0x184d0 0x4>; status = "okay"; }; I dumped some raw samples of the temperature fields in each of these registers. This CSV contains the raw values converted to decimal. http://pastebin.com/Umc3cy5L The first column is the current register at 0x182b0 27:19 and the second is the register at 0x184c4 9:1. Here's a quick plot of a larger sample size while the temperature was rising. https://imgur.com/E9HlSBx The blue value is the current 0x182b0 register which seems to bounce around the green value from 0x184c4. I'll try a test of instantiating both at the same time and comparing the final output of the driver. On Wed, Feb 25, 2015 at 1:39 PM, Eduardo Valentin <edubezval@gmail.com> wrote: >> Does that new thermal sensors only improve the stability or does it >> also modify the value? >> >> In the second case it will more or less break the user space expectation. > > Yeah, I agree here. We need to understand if this is: > (1) a fix of which register to use. In that case, the old dtbs are > essentially wrong, and the driver would need to adapt, I would say. > (2) a way to report better temperature extrapolations. then, this is > essentially a new temp sensor, and we should have two separated > compatible. in other words, just keep the patch the way it is. This *might* be a different physical sensor, or it could be from the same source with some averaging/filtering applied in hardware. The conversion formula is the same, however, and I get similar raw values from both. > Yes. Typically I ask to see the complete series, even if I am not taking > the DTS changes. That is, you send a complete series, with changes in > the kernel code and in the DTS, copying the required audience (from > kernel side and from DT side). Once the changes are accepted, the > patches will be picked by the correct tree maintainer. It is common that > DTS changes go via the platform tree, to avoid conflicts though. Thanks for the clarification. I'll send both in the next version as I suspect there will be a v2 of this change. -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Gregory, I instantiated both configurations and verified I get essentially the same temperature from both, with the original register having a slightly larger spread. I didn't reproduce any outliers in this run, but I'll keep it running for a while to see if any occur. I'm running this to gather samples. # while true; do echo $(</sys/class/thermal/thermal_zone0/temp), $(</sys/class/thermal/thermal_zone1/temp); done https://i.imgur.com/c5wfPuy.png I just got some information from our vendor indicating there's an erratum for the register I'm proposing to use. The workaround is to read repeatedly until the value is consistent. I still have open questions: 1. Why is the current register exhibiting behavior that would be described by the erratum while the proposed register seems more reliable? 2. What is the underlying hardware difference between the two? This is my hardware revision, though the registers in question appear in the functional spec for Armada XP, so I would think they would apply to all flavors. mvebu-soc-id: MVEBU SoC ID=0x7846, Rev=0x2 Hopefully either of our queries will be answered and we can make a more informed decision on this. Thanks, Tyler On Wed, Feb 25, 2015 at 2:47 PM, Tyler Hall <tylerwhall@gmail.com> wrote: > Hi Gregory, Eduardo, > > On Wed, Feb 25, 2015 at 05:10:14PM +0100, Gregory CLEMENT wrote: >> By using it by default do you mean removing marvell,armadaxp-thermal >> and adding armadaxp-filtered-thermal instead ? > > Yes, replacing it in device tree. For me, > /sys/class/thermal/thermal_zone0/temp returns the same temperature but > with less variability between samples. My intent was to switch the > source of the data and not affect user space other than providing a > more stable reading. > >> Tyler, >> In the meantime could you double check your values? The temperature on my board >> seemed broken on my board. If needed I can check on an other board. By the way >> on which board/product did you try it? > > I'm on a custom board with the 4-core MV78460. In addition to my > patch, this is new device tree entry. > > thermal@184c4 { > compatible = "marvell,armadaxp-filtered-thermal"; > reg = <0x184c4 0x4 > 0x184d0 0x4>; > status = "okay"; > }; > > I dumped some raw samples of the temperature fields in each of these > registers. This CSV contains the raw values converted to decimal. > http://pastebin.com/Umc3cy5L > The first column is the current register at 0x182b0 27:19 and the > second is the register at 0x184c4 9:1. > > Here's a quick plot of a larger sample size while the temperature was rising. > https://imgur.com/E9HlSBx > The blue value is the current 0x182b0 register which seems to bounce > around the green value from 0x184c4. > > I'll try a test of instantiating both at the same time and comparing > the final output of the driver. > > On Wed, Feb 25, 2015 at 1:39 PM, Eduardo Valentin <edubezval@gmail.com> wrote: >>> Does that new thermal sensors only improve the stability or does it >>> also modify the value? >>> >>> In the second case it will more or less break the user space expectation. >> >> Yeah, I agree here. We need to understand if this is: >> (1) a fix of which register to use. In that case, the old dtbs are >> essentially wrong, and the driver would need to adapt, I would say. >> (2) a way to report better temperature extrapolations. then, this is >> essentially a new temp sensor, and we should have two separated >> compatible. in other words, just keep the patch the way it is. > > This *might* be a different physical sensor, or it could be from the > same source with some averaging/filtering applied in hardware. The > conversion formula is the same, however, and I get similar raw values > from both. > >> Yes. Typically I ask to see the complete series, even if I am not taking >> the DTS changes. That is, you send a complete series, with changes in >> the kernel code and in the DTS, copying the required audience (from >> kernel side and from DT side). Once the changes are accepted, the >> patches will be picked by the correct tree maintainer. It is common that >> DTS changes go via the platform tree, to avoid conflicts though. > > Thanks for the clarification. I'll send both in the next version as I > suspect there will be a v2 of this change. -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/Documentation/devicetree/bindings/thermal/armada-thermal.txt b/Documentation/devicetree/bindings/thermal/armada-thermal.txt index 4698e0e..0d6a3f1 100644 --- a/Documentation/devicetree/bindings/thermal/armada-thermal.txt +++ b/Documentation/devicetree/bindings/thermal/armada-thermal.txt @@ -7,6 +7,14 @@ Required properties: marvell,armada375-thermal marvell,armada380-thermal marvell,armadaxp-thermal + marvell,armadaxp-filtered-thermal + + Note: "marvell,armadaxp-filtered-thermal" is adjusted to read + the hardware-filtered value in the thermal manager + control/status register rather than the raw sensor value in the + thermal sensor status register. "marvell,armadaxp-thermal" + remains for backward compatibility. The sensor reg address must + also point to the appropriate register. - reg: Device's register space. Two entries are expected, see the examples below. diff --git a/drivers/thermal/armada_thermal.c b/drivers/thermal/armada_thermal.c index c2556cf..d3c2ad3 100644 --- a/drivers/thermal/armada_thermal.c +++ b/drivers/thermal/armada_thermal.c @@ -196,6 +196,15 @@ static const struct armada_thermal_data armadaxp_data = { .coef_div = 13825, }; +static const struct armada_thermal_data armadaxp_filt_data = { + .init_sensor = armadaxp_init_sensor, + .temp_shift = 1, + .temp_mask = 0x1ff, + .coef_b = 3153000000UL, + .coef_m = 10000000UL, + .coef_div = 13825, +}; + static const struct armada_thermal_data armada370_data = { .is_valid = armada_is_valid, .init_sensor = armada370_init_sensor, @@ -236,6 +245,10 @@ static const struct of_device_id armada_thermal_id_table[] = { .data = &armadaxp_data, }, { + .compatible = "marvell,armadaxp-filtered-thermal", + .data = &armadaxp_filt_data, + }, + { .compatible = "marvell,armada370-thermal", .data = &armada370_data, },
The current register being used to read the temperature returns a noisy value that is prone to variance and occasional outliers. The value in the thermal manager control and status register appears to have the same scale but much less variability. Add a "marvell,armadaxp-filtered-thermal" config which is set up to read from the Thermal Manager Control and Status Register at 0x184c4 rather than the Thermal Sensor Status Register at 0x182b0. The only difference is the temperature value shift. The original "marvell,armadaxp-thermal" is retained for device tree compatibility. This also fixes Armada XP clearing the disable bit in the wrong register. Bit 0 of the sensor register was being cleared but that bit is read-only. The disable bit doesn't seem to have an effect on the temperature sensor value, however, so this doesn't make a material difference. This problem was detected when running with the watchdog(8) daemon polling the thermal value. In one instance I observed a single read of over 200 degrees C which caused a spurious watchdog-initiated reboot. I have since observed individual outliers of ~20 degrees C. With this change and the corresponding device tree update, the temperature is much more stable. Signed-off-by: Tyler Hall <tylerwhall@gmail.com> --- If there's a better way to handle this than a separate binding, I'm open to suggestions. My conclusions about these registers are based on experimental data. The documentation is very sparse, but the Thermal Manager Control and Status Register looks like the preferred register given the way it is laid out in the public spec. I have the small corresponding patch to the dts which I can submit separately. Thanks Tyler .../devicetree/bindings/thermal/armada-thermal.txt | 8 ++++++++ drivers/thermal/armada_thermal.c | 13 +++++++++++++ 2 files changed, 21 insertions(+)