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([2600:8803:e7e4:500:46d5:c880:64c8:f854]) by smtp.gmail.com with ESMTPSA id 5614622812f47-44da3e48249sm2013281b6e.5.2025.10.27.13.36.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Oct 2025 13:36:34 -0700 (PDT) Message-ID: <506feaa8-5808-48d4-8cc7-baadd8f43976@baylibre.com> Date: Mon, 27 Oct 2025 15:36:33 -0500 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] iio: adc: qcom-pm8xxx-xoadc: fix incorrect calibration values To: Antony Kurniawan Soemardi , Jonathan Cameron , =?UTF-8?Q?Nuno_S=C3=A1?= , Andy Shevchenko Cc: linux-arm-msm@vger.kernel.org, linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org References: <20251028-pm8xxx-xoadc-fix-v1-0-b000e1036e41@smankusors.com> <20251028-pm8xxx-xoadc-fix-v1-2-b000e1036e41@smankusors.com> <0eea7e4c-ec3b-421c-8522-aa3f52b5cb13@baylibre.com> <003c5cf7-2498-4ff3-a8b4-2911941b1464@smankusors.com> Content-Language: en-US From: David Lechner In-Reply-To: <003c5cf7-2498-4ff3-a8b4-2911941b1464@smankusors.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 10/27/25 2:53 PM, Antony Kurniawan Soemardi wrote: > On 10/28/2025 1:35 AM, David Lechner wrote: >> On 10/27/25 12:29 PM, Antony Kurniawan Soemardi wrote: >>> On msm8960 phones, the XOADC driver was using incorrect calibration >>> values: >>> absolute calibration dx = 625000 uV, dy = 4 units >>> ratiometric calibration dx = 1800, dy = -29041 units >>> >>> As a result, reading from the IIO bus returned unexpected results: >>> in_voltage_7 (USB_VBUS): 0 >>> in_voltage_10 (125V): 0 >>> >>> The issue was caused by not setting the ratiometric scale (amux_ip_rsv) >>> from the predefined channels. Additionally, the downstream code always >> Mentioning downstream kernels is usually a red flag. :-) >> >> We can justify it here though by saying that there is no documentation >> available other than downstream source code, so we are just using it >> as a reference. > ah ok, rewording needed then >>> set the ADC_ARB_USRP_DIG_PARAM register to PM8XXX_ADC_ARB_ANA_DIG [1]. >>> That value does not include the SEL_SHIFT0 and SEL_SHIFT1 bits. Enabling >>> those bits caused calibration errors too, so they were removed. >>> >>> With these fixes, calibration now uses the correct values: >>> absolute calibration dx = 625000 uV, dy = 6307 units >>> ratiometric calibration dx = 1800, dy = 18249 units >>> >>> Reading from the IIO bus now returns expected results: >>> in_voltage_7 (USB_VBUS): 4973836 >>> in_voltage_10 (125V): 1249405 >> Would be useful to mention which hardware you tested with in case >> it turns out that there is some other hardware that does require the >> SHIFT0/1 bits to be set. > I did mention Sony Xperia SP from cover letter, but I haven't > referenced it in this commit yet. Also I tried to search on Github for > SHIFT0/1 bits, but couldn't find any usage of them... >>> [1] https://github.com/LineageOS/android_kernel_sony_msm8960t/blob/93319b1e5aa343ec1c1aabcb028c5e88c7df7c01/drivers/hwmon/pm8xxx-adc.c#L407-L408 >>> >> Since this is a fix, it should have a Fixes: tag. And it sounds like >> possibly two separate fixes. In that case, it should be two separate >> patches. > Fixes into 63c3ecd946d4ae2879ec0d8c6dcb90132a74d831? The correct format is: Fixes: 63c3ecd946d4 ("iio: adc: add a driver for Qualcomm PM8xxx HK/XOADC") See: https://www.kernel.org/doc/html/latest/process/submitting-patches.html#describe-changes >>> Signed-off-by: Antony Kurniawan Soemardi >>> --- >>>   drivers/iio/adc/qcom-pm8xxx-xoadc.c | 10 ++++++---- >>>   1 file changed, 6 insertions(+), 4 deletions(-) >>> >>> diff --git a/drivers/iio/adc/qcom-pm8xxx-xoadc.c b/drivers/iio/adc/qcom-pm8xxx-xoadc.c >>> index 8555f34036fb13c41ac720dc02c1dc39876e9198..a53d361456ec36b66d258041877bd96ab37838c4 100644 >>> --- a/drivers/iio/adc/qcom-pm8xxx-xoadc.c >>> +++ b/drivers/iio/adc/qcom-pm8xxx-xoadc.c >>> @@ -503,10 +503,11 @@ static int pm8xxx_read_channel_rsv(struct pm8xxx_xoadc *adc, >>>           goto unlock; >>>         /* Decimation factor */ >>> -    ret = regmap_write(adc->map, ADC_ARB_USRP_DIG_PARAM, >>> -               ADC_ARB_USRP_DIG_PARAM_SEL_SHIFT0 | >>> -               ADC_ARB_USRP_DIG_PARAM_SEL_SHIFT1 | >>> -               ch->decimation << ADC_DIG_PARAM_DEC_SHIFT); >>> +    ret = regmap_update_bits(adc->map, >>> +                 ADC_ARB_USRP_DIG_PARAM, >>> +                 ADC_ARB_USRP_DIG_PARAM_DEC_RATE0 | >>> +                 ADC_ARB_USRP_DIG_PARAM_DEC_RATE1, >>> +                 ch->decimation << ADC_DIG_PARAM_DEC_SHIFT); >> As a follow-up patch, it would be nice to update the driver to use FIELD_PREP(). >> >> I.e. remove ADC_ARB_USRP_DIG_PARAM_DEC_RATE0, ADC_ARB_USRP_DIG_PARAM_DEC_RATE1 >> and ADC_DIG_PARAM_DEC_SHIFT macros and replace them with one macro: >> >> #define ADC_ARB_USRP_DIG_PARAM_DEC_RATE        GENMASK(6, 5) >> >> Then use it like: >> >>     ret = regmap_update_bits(adc->map, >>                  ADC_ARB_USRP_DIG_PARAM, >>                  ADC_ARB_USRP_DIG_PARAM_DEC_RATE, >>                  FIELD_PREP(ADC_ARB_USRP_DIG_PARAM_DEC_RATE, >>                         ch->decimation)); >> >> This should be done for all of the similar multi-bit fields. > as a follow up patch, you mean next version of this patch series, or > separate patch series? Either way is fine. It's just a "nice to have" change. >>>       if (ret) >>>           goto unlock; >>>   @@ -783,6 +784,7 @@ static int pm8xxx_xoadc_parse_channel(struct device *dev, >>>       ch->calibration = VADC_CALIB_ABSOLUTE; >>>       /* Everyone seems to use default ("type 2") decimation */ >>>       ch->decimation = VADC_DEF_DECIMATION; >>> +    ch->amux_ip_rsv = hwchan->amux_ip_rsv; >>>         if (!fwnode_property_read_u32(fwnode, "qcom,ratiometric", &rsv)) { >>>           ch->calibration = VADC_CALIB_RATIOMETRIC; >>> >