Re: [PATCH RESEND v6 1/5] hwmon: (pmbus/core): Add interrupt support

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Hi Guenter

On 03-01-2023 05:56 pm, Guenter Roeck wrote:
On Tue, Jan 03, 2023 at 12:18:49PM +0530, Naresh Solanki wrote:
Hi Guenter,

On 29-12-2022 08:10 pm, Guenter Roeck wrote:
On Wed, Dec 14, 2022 at 09:07:11AM +0100, Naresh Solanki wrote:
From: Patrick Rudolph <patrick.rudolph@xxxxxxxxxxxxx>

Implement PMBUS irq handler.

Signed-off-by: Patrick Rudolph <patrick.rudolph@xxxxxxxxxxxxx>
Signed-off-by: Naresh Solanki <Naresh.Solanki@xxxxxxxxxxxxx>

$ scripts/checkpatch.pl --strict index.html
CHECK: Blank lines aren't necessary after an open brace '{'
#131: FILE: drivers/hwmon/pmbus/pmbus_core.c:3088:
+	for (i = 0; i < data->info->pages; i++) {
+

CHECK: Alignment should match open parenthesis
#183: FILE: drivers/hwmon/pmbus/pmbus_core.c:3140:
+	ret = devm_request_threaded_irq(dev, client->irq, NULL, pmbus_fault_handler,
+			      0, "pmbus-irq", data);

CHECK: Please use a blank line after function/struct/union/enum declarations
#197: FILE: drivers/hwmon/pmbus/pmbus_core.c:3154:
   }
+static int pmbus_irq_setup(struct i2c_client *client, struct pmbus_data *data)

total: 0 errors, 0 warnings, 3 checks, 109 lines checked

NOTE: For some of the reported defects, checkpatch may be able to
        mechanically convert to the typical style using --fix or --fix-inplace.

index.html has style problems, please review.

Please run checkpatch --strict on your patches.
Also see Documentation/hwmon/submitting-patches.rst.
I will take care of these errors in the updated version.

---
   drivers/hwmon/pmbus/pmbus.h      |  2 +-
   drivers/hwmon/pmbus/pmbus_core.c | 84 ++++++++++++++++++++++++++++++++
   2 files changed, 85 insertions(+), 1 deletion(-)


base-commit: 364ffd2537c44cb6914ff5669153f4a86fffad29

diff --git a/drivers/hwmon/pmbus/pmbus.h b/drivers/hwmon/pmbus/pmbus.h
index 10fb17879f8e..6b2e6cf93b19 100644
--- a/drivers/hwmon/pmbus/pmbus.h
+++ b/drivers/hwmon/pmbus/pmbus.h
@@ -26,7 +26,7 @@ enum pmbus_regs {
   	PMBUS_CAPABILITY		= 0x19,
   	PMBUS_QUERY			= 0x1A,
-
+	PMBUS_SMBALERT_MASK		= 0x1B,
   	PMBUS_VOUT_MODE			= 0x20,
   	PMBUS_VOUT_COMMAND		= 0x21,
   	PMBUS_VOUT_TRIM			= 0x22,
diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
index 95e95783972a..244fd2597252 100644
--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c
@@ -3072,11 +3072,89 @@ static int pmbus_regulator_register(struct pmbus_data *data)
   	return 0;
   }
+
+static int pmbus_write_smbalert_mask(struct i2c_client *client, u8 page, u8 reg, u8 val)
+{
+	return pmbus_write_word_data(client, page, PMBUS_SMBALERT_MASK, reg | (val << 8));
+}
+
+static irqreturn_t pmbus_fault_handler(int irq, void *pdata)
+{
+	struct pmbus_data *data = pdata;
+	struct i2c_client *client = to_i2c_client(data->dev);
+	int i, status;
+
+	for (i = 0; i < data->info->pages; i++) {
+
+		mutex_lock(&data->update_lock);
+		status = pmbus_read_status_word(client, i);
+		if (status < 0) {
+			mutex_unlock(&data->update_lock);
+			return status;
+		}
+
+		if (status & ~(PB_STATUS_OFF | PB_STATUS_BUSY | PB_STATUS_POWER_GOOD_N))
+			pmbus_clear_fault_page(client, i);
+
+		mutex_unlock(&data->update_lock);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int pmbus_irq_setup(struct i2c_client *client, struct pmbus_data *data)
+{
+	struct device *dev = &client->dev;
+	const struct pmbus_regulator_status_category *cat;
+	const struct pmbus_regulator_status_assoc *bit;
+	int i, j, err, ret, func;
+	u8 mask;
+
+	for (i = 0; i < data->info->pages; i++) {
+		func = data->info->func[i];
+
+		for (j = 0; j < ARRAY_SIZE(pmbus_regulator_flag_map); j++) {
+			cat = &pmbus_regulator_flag_map[j];
+			if (!(func & cat->func))
+				continue;
+			mask = 0;
+			for (bit = cat->bits; bit->pflag; bit++)
+				mask |= bit->pflag;
+
+			err = pmbus_write_smbalert_mask(client, i, cat->reg, ~mask);
+			if (err)
+				dev_err(dev, "Failed to set smbalert for reg 0x%02x\n",	cat->reg);

This concerns me. It might mean that the chip does not support
PMBUS_SMBALERT_MASK. If so, there would be lots of error messages.
After going through the PMBus specification, it appears that this should not
be an issue unless there is a violation of the specification.

PMBus chips have lots of issues which violate the specification.
Have a look at the various drivers and the workarounds implemented there.
You'll need to check if the command/register is supported before using it.
Also, if you want to keep the error message, make it dev_err_once().

Either case, an error is an error, not to be ignored. An error here
should result in an error abort.
Yes, I agree that PMBus chips can have issues that violate the specification, and that it is important to check whether a command or register is supported before using it. I have noticed that many drivers use the PMBUS_HAVE_* flags to expose the presence of specific registers, and I think it would be a good idea to add a PMBUS_HAVE_SMBALERT flag as well, so that drivers for supported chips can use it to determine whether they should set up an IRQ handler or not. If PMBUS_HAVE_SMBALERT is set, then the IRQ handler should be set up, otherwise it should be ignored.
Will this approach be right?


+		}
+
+		pmbus_write_smbalert_mask(client, i, PMBUS_STATUS_CML, 0xff);
+		pmbus_write_smbalert_mask(client, i, PMBUS_STATUS_OTHER, 0xff);
+		pmbus_write_smbalert_mask(client, i, PMBUS_STATUS_MFR_SPECIFIC, 0xff);

Why check the return value from pmbus_write_smbalert_mask above but not here ?
Thank you for pointing out the oversight. I will make sure to include an
error check at this point.

+		if (data->info->func[i] & PMBUS_HAVE_FAN12)
+			pmbus_write_smbalert_mask(client, i, PMBUS_STATUS_FAN_12, 0xff);
+		if (data->info->func[i] & PMBUS_HAVE_FAN34)
+			pmbus_write_smbalert_mask(client, i, PMBUS_STATUS_FAN_34, 0xff);
+	}
+
+	/* Register notifiers - can fail if IRQ is not given */

The comment does not make sense. pmbus_irq_setup() is not called
if the interrupt "is not given".
Yes. The comment here is not relevant and will be removed.

+	ret = devm_request_threaded_irq(dev, client->irq, NULL, pmbus_fault_handler,
+			      0, "pmbus-irq", data);
+	if (ret) {
+		dev_warn(dev, "IRQ disabled %d\n", ret);

This is not a warning, it is an error.
Thank you for bringing this to my attention. I will make sure to update the
code to reflect that this is an error.

+		return ret;
+	}
+
+	return 0;
+}
+
   #else

This is still in regulator code. I said several times that this is not
acceptable.
Thank you for pointing out the mistake. I will make sure to correct this in
the next revision.

   static int pmbus_regulator_register(struct pmbus_data *data)
   {
   	return 0;
   }
+static int pmbus_irq_setup(struct i2c_client *client, struct pmbus_data *data)
+{
+	return 0;
+}
   #endif
   static struct dentry *pmbus_debugfs_dir;	/* pmbus debugfs directory */
@@ -3441,6 +3519,12 @@ int pmbus_do_probe(struct i2c_client *client, struct pmbus_driver_info *info)
   	if (ret)
   		return ret;
+	if (client->irq > 0) {
+		ret = pmbus_irq_setup(client, data);
+		if (ret)
+			return ret;
+	}
+
   	ret = pmbus_init_debugfs(client, data);
   	if (ret)
   		dev_warn(dev, "Failed to register debugfs\n");

Thanks,
Naresh



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