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Message-ID: <9df50a4c-c73f-e66a-d5ed-ab381d743c32@caviumnetworks.com>
Date: Tue, 13 Feb 2018 15:06:46 -0800
From: David Daney <ddaney@...iumnetworks.com>
To: Andy Shevchenko <andy.shevchenko@...il.com>,
David Daney <david.daney@...ium.com>
Cc: Alessandro Zummo <a.zummo@...ertech.it>,
Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
Rob Herring <robh+dt@...nel.org>,
Mark Rutland <mark.rutland@....com>, linux-rtc@...r.kernel.org,
devicetree <devicetree@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] rtc: isl12026: Add driver.
On 02/13/2018 07:54 AM, Andy Shevchenko wrote:
[...]
>> diff --git a/drivers/rtc/rtc-isl12026.c b/drivers/rtc/rtc-isl12026.c
>> new file mode 100644
>> index 000000000000..a5f04e0faceb
>> --- /dev/null
>> +++ b/drivers/rtc/rtc-isl12026.c
>> @@ -0,0 +1,550 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * An I2C driver for the Intersil ISL 12026
>> + *
>> + * Copyright (c) 2018 Cavium, Inc.
>> + */
>
>> +#include <linux/types.h>
>> +#include <linux/nvmem-provider.h>
>> +#include <linux/of_device.h>
>> +#include <linux/module.h>
>> +#include <linux/delay.h>
>> +#include <linux/mutex.h>
>> +#include <linux/slab.h>
>> +#include <linux/bcd.h>
>> +#include <linux/i2c.h>
>> +#include <linux/rtc.h>
>> +#include <linux/of.h>
>
> Perhaps in alphabetical order.
Done.
>
>> +/* register offsets */
>> +#define ISL12026_REG_SC 0x30
>> +
>> +#define ISL12026_REG_SR 0x3f
>> +# define ISL12026_REG_SR_RTCF BIT(0)
>> +# define ISL12026_REG_SR_WEL BIT(1)
>> +# define ISL12026_REG_SR_RWEL BIT(2)
>> +# define ISL12026_REG_SR_MBZ BIT(3)
>> +# define ISL12026_REG_SR_OSCF BIT(4)
>> +
>> +/* ISL register bits */
>> +#define ISL12026_HR_MIL BIT(7) /* military or 24 hour time */
>> +
>
>> +#define ISL12026_REG_PWR 0x14
>
> Perhaps keep it ordered? (0x14 < 0x30 obviously)
Done.
>
>> +# define ISL12026_REG_PWR_BSW BIT(6)
>> +# define ISL12026_REG_PWR_SBIB BIT(7)
>
[...]
>> +
>> +static int isl12026_rtc_set_time(struct device *dev, struct rtc_time *tm)
>> +{
>> + struct i2c_client *client = to_i2c_client(dev);
>> + struct isl12026 *priv = i2c_get_clientdata(client);
>
>> + int rv = 0;
>
>> + u8 op[10];
>> +
>> + struct i2c_msg msg = {
>> + .addr = client->addr,
>> + .flags = 0,
>> + .len = 1,
>> + .buf = op
>> + };
>
>> +
>
> Redundant.
>
>> + int ret;
>
> rv, ret, ... ???
I changed everything to use 'ret' to contain values returned from
function calls, and 'rv' for the value the current function will return.
>
>> +
>> + mutex_lock(&priv->lock);
>> +
>> + /* Set SR.WEL */
>> + op[0] = 0;
>> + op[1] = ISL12026_REG_SR;
>> + op[2] = ISL12026_REG_SR_WEL;
>> + msg.len = 3;
>
>> + ret = i2c_transfer(client->adapter, &msg, 1);
>> + if (ret != 1) {
>
> Can it return < 0? If so, why do you shadow the error code?
I think I fixed this driver wide.
>
[...]
>> + ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
>> + if (ret != ARRAY_SIZE(msgs)) {
>> + dev_err(&client->dev, "read error, ret=%d\n", ret);
>> + rv = -EIO;
>> + goto out;
>> + }
>> +
>
>> + if (sr & ISL12026_REG_SR_RTCF)
>> + dev_warn(&client->dev, "Real-Time Clock Failure on read\n");
>> + if (sr & ISL12026_REG_SR_OSCF)
>> + dev_warn(&client->dev, "Oscillator Failure on read\n");
>
> Can you get them together?
> if not, perhaps consider 'else' keyword.
They are independent error indicators, I think it is best to test for
them unconditionally like this.
>
>> +
>> + /* Second, CCR regs */
>> + addr[0] = 0;
>> + addr[1] = ISL12026_REG_SC;
>> + msgs[1].len = sizeof(ccr);
>> + msgs[1].buf = ccr;
>> +
>> + ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
>> + if (ret != ARRAY_SIZE(msgs)) {
>> + dev_err(&client->dev, "read error, ret=%d\n", ret);
>> + rv = -EIO;
>> + goto out;
>> + }
>> +
>
>> + dev_dbg(&client->dev,
>> + "raw data is sec=%02x, min=%02x, hr=%02x, mday=%02x, mon=%02x, year=%02x, wday=%02x, y2k=%02x\n",
>> + ccr[0], ccr[1], ccr[2], ccr[3],
>> + ccr[4], ccr[5], ccr[6], ccr[7]);
>
> Ouch.
>
Not essential, I removed it.
>> +
>> + tm->tm_sec = bcd2bin(ccr[0] & 0x7F);
>> + tm->tm_min = bcd2bin(ccr[1] & 0x7F);
>> + if (ccr[2] & ISL12026_HR_MIL)
>> + tm->tm_hour = bcd2bin(ccr[2] & 0x3F);
>> + else
>> + tm->tm_hour = bcd2bin(ccr[2] & 0x1F) +
>> + ((ccr[2] & 0x20) ? 12 : 0);
>> + tm->tm_mday = bcd2bin(ccr[3] & 0x3F);
>> + tm->tm_mon = bcd2bin(ccr[4] & 0x1F) - 1;
>> + tm->tm_year = bcd2bin(ccr[5]);
>> + if (bcd2bin(ccr[7]) == 20)
>> + tm->tm_year += 100;
>> + tm->tm_wday = ccr[6] & 0x07;
>> +
>> + dev_dbg(&client->dev, "secs=%d, mins=%d, hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
>> + tm->tm_sec, tm->tm_min, tm->tm_hour,
>> + tm->tm_mday, tm->tm_mon, tm->tm_year, tm->tm_wday);
>> + rv = rtc_valid_tm(tm);
>
>> +out:
>> + mutex_unlock(&priv->lock);
>
> Here one pattern, below another...
>
> Hey, you have to learn being consistent.
I made them all like this one. Single function exit point, with the
unlock immediately before the return.
>
>> + return rv;
>> +}
>> +
>> +static const struct rtc_class_ops isl12026_rtc_ops = {
>> + .read_time = isl12026_rtc_read_time,
>> + .set_time = isl12026_rtc_set_time,
>> +};
>> +
>> +static int isl12026_nvm_read(void *p, unsigned int offset,
>> + void *val, size_t bytes)
>> +{
>> + struct isl12026 *priv = p;
>> + int r;
>> + u8 addr[2];
>> + struct i2c_msg msgs[] = {
>> + {
>> + .addr = priv->nvm_client->addr,
>> + .flags = 0,
>> + .len = sizeof(addr),
>> + .buf = addr
>> + },
>> + {
>> + .addr = priv->nvm_client->addr,
>> + .flags = I2C_M_RD,
>> + .buf = val
>> + }
>> + };
>> +
>> + if (offset >= priv->nvm_cfg.size)
>> + return 0; /* End-of-file */
>> + if (offset + bytes > priv->nvm_cfg.size)
>> + bytes = priv->nvm_cfg.size - offset;
>> +
>
>> + addr[0] = (offset >> 8) & 0xff;
>> + addr[1] = offset & 0xff;
>
> Useless & 0xff:s.
They may be redundant, but they clearly should the intention of shifting
and masking the individual address component bytes out of the specified
offset. I would like to leave them in for clarity.
>
> Isn't endianess handled by i2c core?
There is no concept of endianess in i2c, at the protocol level it it
just an array of bytes transmitted to and from the device. We have to
put the bytes in the order expected by the target.
>
>> + msgs[1].len = bytes;
>> + mutex_lock(&priv->lock);
>
>> + r = i2c_transfer(priv->nvm_client->adapter, msgs, ARRAY_SIZE(msgs));
>> +
>> + mutex_unlock(&priv->lock);
>> +
>> + if (r != ARRAY_SIZE(msgs)) {
>
> A bit unusual pattern,
>
> what about
>
> mutex_lock();
> r = ...;
> if (r...) {
> ...
> mutex_unlock();
> return -Exxx;
> }
> mutex_unlock();
Multiple exit points when using locks invites coding errors where you
miss the unlock in some error path that is not tested.
>
> ?
>
>> + dev_err(priv->nvm_cfg.dev, "nvmem read error, ret=%d\n", r);
>> + return -EIO;
>> + }
>> +
>> + return bytes;
>> +}
>> +
>> +static int isl12026_nvm_write(void *p, unsigned int offset,
>> + void *val, size_t bytes)
>> +{
>> + struct isl12026 *priv = p;
>
>> + int r;
>
> Use consistent style, either r everywhere, or ret, or rc, or rval.
I hope it is better in the next version.
>
>> + u8 *v = val;
>> + size_t chunk_size, num_written;
>> + u8 payload[ISL12026_PAGESIZE + 2]; /* page + 2 address bytes */
>> + struct i2c_msg msgs[] = {
>> + {
>> + .addr = priv->nvm_client->addr,
>> + .flags = 0,
>> + .buf = payload
>> + }
>> + };
>> +
>> + if (offset >= priv->nvm_cfg.size)
>> + return 0; /* End-of-file */
>> + if (offset + bytes > priv->nvm_cfg.size)
>> + bytes = priv->nvm_cfg.size - offset;
>> +
>> + mutex_lock(&priv->lock);
>> +
>> + num_written = 0;
>> + while (bytes) {
>> + chunk_size = round_down(offset, ISL12026_PAGESIZE) +
>> + ISL12026_PAGESIZE - offset;
>> + chunk_size = min(bytes, chunk_size);
>> + memcpy(payload + 2, v + num_written, chunk_size);
>
>> + payload[0] = (offset >> 8) & 0xff;
>> + payload[1] = offset & 0xff;
>
> Useless & 0xff:s.
>
> Isn't endianess handled by i2c core?
See above.
>
>> + msgs[0].len = chunk_size + 2;
>> + r = i2c_transfer(priv->nvm_client->adapter,
>> + msgs, ARRAY_SIZE(msgs));
>> + if (r != ARRAY_SIZE(msgs)) {
>> + dev_err(priv->nvm_cfg.dev,
>> + "nvmem write error, ret=%d\n", r);
>> + break;
>> + }
>> + bytes -= chunk_size;
>> + offset += chunk_size;
>> + num_written += chunk_size;
>> + msleep(ISL12026_NVMEM_WRITE_TIME);
>> + }
>> +
>> + mutex_unlock(&priv->lock);
>> +
>> + return num_written > 0 ? num_written : -EIO;
>> +}
>> +
>> +static int isl12026_probe(struct i2c_client *client,
>> + const struct i2c_device_id *id)
>> +{
>> + struct isl12026 *priv;
>> + int pwr, requested_pwr;
>> + int ret;
>> + u32 bsw_val, sbib_val;
>> + bool set_bsw, set_sbib;
>
>> + priv = devm_kzalloc(&client->dev, sizeof(struct isl12026), GFP_KERNEL);
>> + if (!priv)
>> + return -ENOMEM;
>
> sizeof(*priv) ?
sure.
>
>> + ret = of_property_read_u32(client->dev.of_node,
>> + "isil,pwr-bsw", &bsw_val);
>> + set_bsw = (ret == 0);
>> +
>> + ret = of_property_read_u32(client->dev.of_node,
>> + "isil,pwr-sbib", &sbib_val);
>> + set_sbib = (ret == 0);
>> +
>> + /* Check if PWR.BSW and/or PWR.SBIB need specified values */
>> +
>> + if (set_bsw || set_sbib) {
>> + pwr = isl12026_read_reg(client, ISL12026_REG_PWR);
>> + if (pwr < 0)
>> + dev_err(&client->dev,
>> + "Error: Failed to read PWR %d\n", pwr);
>
> ...and what? No recovery? No nothing except the message?
I will bail out of this setting or power handling if this happens, that
seems like all that we could do.
>
>> +
>> + requested_pwr = pwr;
>> +
>> + if (set_bsw) {
>> + if (bsw_val)
>> + requested_pwr |= ISL12026_REG_PWR_BSW;
>> + else
>> + requested_pwr &= ~ISL12026_REG_PWR_BSW;
>> + }
>> + if (set_sbib) {
>> + if (sbib_val)
>> + requested_pwr |= ISL12026_REG_PWR_SBIB;
>> + else
>> + requested_pwr &= ~ISL12026_REG_PWR_SBIB;
>> + }
>> +
>> + if (pwr >= 0 && pwr != requested_pwr) {
>> + dev_info(&client->dev, "PWR: %02x\n", pwr);
>> + dev_info(&client->dev,
>> + "Updating PWR to: %02x\n", (u8)requested_pwr);
>> + isl12026_write_reg(client,
>> + ISL12026_REG_PWR, requested_pwr);
>> + }
>> + }
>
> Can you refactor above to a separate function?
Done.
>
>> + priv->rtc = devm_rtc_device_register(&client->dev, "rtc-isl12026",
>> + &isl12026_rtc_ops, THIS_MODULE);
>
>> +
>
> Redundant empty line.
>
>> + ret = PTR_ERR_OR_ZERO(priv->rtc);
>> + if (ret)
>> + return ret;
>
>
>> + if (IS_ENABLED(CONFIG_NVMEM)) {
>
> I think you don't need this, see below.
>
>> + priv->nvm_client = i2c_new_dummy(client->adapter, 0x57);
>> + if (!priv->nvm_client)
>> + return -ENOMEM;
>
> i2c_new_secondary_device() ?
>
>> + priv->nvm_dev = nvmem_register(&priv->nvm_cfg);
>> +
>
> Redundant empty line.
>
>> + if (!priv->nvm_dev)
>
> Should it be IS_ERR() ?
>
>> + return -ENOMEM;
>
> After all rtc_nvmem_register() ?
Yes, I switched to using that.
>
>> + }
>> + return 0;
>> +}
>> +
>> +static int isl12026_remove(struct i2c_client *client)
>> +{
>> + struct isl12026 *priv = i2c_get_clientdata(client);
>> +
>
>> + if (priv->nvm_dev)
>
> How is it
>
>> + nvmem_unregister(priv->nvm_dev);
>
>
>> + if (priv->nvm_client)
>
> Check with v4.16-rc1. This is duplicate check.
Yes.
>
>> + i2c_unregister_device(priv->nvm_client);
>> +
>> + return 0;
>> +}
>
>> +#ifdef CONFIG_OF
>
> Useless.
>
>> +static const struct of_device_id isl12026_dt_match[] = {
>> + { .compatible = "isil,isl12026" },
>> + { },
>> +};
>> +MODULE_DEVICE_TABLE(of, isl12026_dt_match);
>> +#endif
>> +
>
>> +static const struct i2c_device_id isl12026_id[] = {
>> + { "isl12026", 0 },
>> + { }
>> +};
>> +MODULE_DEVICE_TABLE(i2c, isl12026_id);
>
> Useless. Use ->probe_new() approach.
>
>> +#ifdef CONFIG_OF
>
> Ugly and useless.
>
>> + .of_match_table = of_match_ptr(isl12026_dt_match),
>> +#endif
>
Should be better in the next version.
Thanks for the review,
David Daney
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