devicetree.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Chu Lin <linchuyuan@google.com>
To: linchuyuan@google.com, jdelvare@suse.com, linux@roeck-us.net,
	robh+dt@kernel.org, linux-hwmon@vger.kernel.org,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v4 2/2] hwmon: pmbus: max20730: adjust the vout reading given voltage divider
Date: Sun,  4 Oct 2020 03:14:45 +0000	[thread overview]
Message-ID: <20201004031445.2321090-3-linchuyuan@google.com> (raw)
In-Reply-To: <20201004031445.2321090-1-linchuyuan@google.com>

Problem:
We use voltage dividers so that the voltage presented at the voltage
sense pins is confusing. We might need to convert these readings to more
meaningful readings given the voltage divider.

Solution:
Read the voltage divider resistance from dts and convert the voltage
reading to a more meaningful reading.

Testing:
max20730 with voltage divider

Signed-off-by: Chu Lin <linchuyuan@google.com>
---
ChangeLog v1 -> v2
  hwmon: pmbus: max20730:
  - Don't do anything to the ret if an error is returned from pmbus_read_word
  - avoid overflow when doing multiplication

ChangeLog v2 -> v3
  dt-bindings: hwmon: max20730:
  - Provide the binding documentation in yaml format
  hwmon: pmbus: max20730:
  - No change

ChangeLog v3 -> v4
  dt-bindings: hwmon: max20730:
  - Fix highefficiency to high efficiency in description
  - Fix presents to present in vout-voltage-divider
  - Add additionalProperties: false
  hwmon: pmbus: max20730:
  - No change

 drivers/hwmon/pmbus/max20730.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/hwmon/pmbus/max20730.c b/drivers/hwmon/pmbus/max20730.c
index a151a2b588a5..fbf2f1e6c969 100644
--- a/drivers/hwmon/pmbus/max20730.c
+++ b/drivers/hwmon/pmbus/max20730.c
@@ -31,6 +31,7 @@ struct max20730_data {
 	struct pmbus_driver_info info;
 	struct mutex lock;	/* Used to protect against parallel writes */
 	u16 mfr_devset1;
+	u32 vout_voltage_divider[2];
 };
 
 #define to_max20730_data(x)  container_of(x, struct max20730_data, info)
@@ -114,6 +115,14 @@ static int max20730_read_word_data(struct i2c_client *client, int page,
 		max_c = max_current[data->id][(data->mfr_devset1 >> 5) & 0x3];
 		ret = val_to_direct(max_c, PSC_CURRENT_OUT, info);
 		break;
+	case PMBUS_READ_VOUT:
+		ret = pmbus_read_word_data(client, page, phase, reg);
+		if (ret > 0 && data->vout_voltage_divider[0] && data->vout_voltage_divider[1]) {
+			u64 temp = DIV_ROUND_CLOSEST_ULL((u64)ret * data->vout_voltage_divider[1],
+							 data->vout_voltage_divider[0]);
+			ret = clamp_val(temp, 0, 0xffff);
+		}
+		break;
 	default:
 		ret = -ENODATA;
 		break;
@@ -364,6 +373,15 @@ static int max20730_probe(struct i2c_client *client,
 	data->id = chip_id;
 	mutex_init(&data->lock);
 	memcpy(&data->info, &max20730_info[chip_id], sizeof(data->info));
+	if (of_property_read_u32_array(client->dev.of_node, "vout-voltage-divider",
+				       data->vout_voltage_divider,
+				       ARRAY_SIZE(data->vout_voltage_divider)) != 0)
+		memset(data->vout_voltage_divider, 0, sizeof(data->vout_voltage_divider));
+	if (data->vout_voltage_divider[1] < data->vout_voltage_divider[0]) {
+		dev_err(dev,
+			"The total resistance of voltage divider is less than output resistance\n");
+		return -ENODEV;
+	}
 
 	ret = i2c_smbus_read_word_data(client, MAX20730_MFR_DEVSET1);
 	if (ret < 0)
-- 
2.28.0.806.g8561365e88-goog


  parent reply	other threads:[~2020-10-04  3:14 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-04  3:14 [PATCH v4 0/2] hwmon: pmbus: max20730: adjust the vout base on Chu Lin
2020-10-04  3:14 ` [PATCH v4 1/2] dt-bindings: hwmon: max20730: adding device tree doc for max20730 Chu Lin
2020-10-06 21:17   ` Rob Herring
2020-10-06 21:55   ` Guenter Roeck
2020-10-04  3:14 ` Chu Lin [this message]
2020-10-04 15:43   ` [PATCH v4 2/2] hwmon: pmbus: max20730: adjust the vout reading given voltage divider Guenter Roeck
2020-10-05  3:07     ` Chu Lin
2020-10-05  5:24       ` Guenter Roeck
2020-10-05 15:03   ` Guenter Roeck
2020-10-06 21:55   ` Guenter Roeck

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20201004031445.2321090-3-linchuyuan@google.com \
    --to=linchuyuan@google.com \
    --cc=devicetree@vger.kernel.org \
    --cc=jdelvare@suse.com \
    --cc=linux-hwmon@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux@roeck-us.net \
    --cc=robh+dt@kernel.org \
    --subject='Re: [PATCH v4 2/2] hwmon: pmbus: max20730: adjust the vout reading given voltage divider' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).