Linux-i2c Archive on lore.kernel.org
 help / color / Atom feed
From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: Chris Packham <chris.packham@alliedtelesis.co.nz>
Cc: Wolfram Sang <wsa@kernel.org>,
	linux-i2c <linux-i2c@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 2/4] i2c: mpc: Interrupt driven transfer
Date: Tue, 13 Apr 2021 16:52:09 +0300
Message-ID: <CAHp75VfR2zNmstvqCSRC2=0hf2DRV7sMdmy9-TDkO07KHwLjGA@mail.gmail.com> (raw)
In-Reply-To: <20210413050956.23264-3-chris.packham@alliedtelesis.co.nz>

On Tue, Apr 13, 2021 at 8:10 AM Chris Packham
<chris.packham@alliedtelesis.co.nz> wrote:
>
> The fsl-i2c controller will generate an interrupt after every byte
> transferred. Make use of this interrupt to drive a state machine which
> allows the next part of a transfer to happen as soon as the interrupt is
> received. This is particularly helpful with SMBUS devices like the LM81
> which will timeout if we take too long between bytes in a transfer.

Also see my other comments below.

...

> +// SPDX-License-Identifier: GPL-2.0

I think it is better to split this with a removal of old stuff and
updating a copyright notice and go as a last one in the series.

...

> +static char *action_str[] = {

static const char * const action_str[]

> +       "invalid",
> +       "start",
> +       "restart",
> +       "read begin",
> +       "read",
> +       "write",
> +       "stop",
> +};

...

> +       dev_dbg(i2c->dev, "%s: action = %s\n", __func__,
> +               action_str[i2c->action]);

Drop useless __func__. With Dynamic Debug enabled it can be turned on
and off at run time.

...

> +                       /* Generate txack on next to last byte */

Tx ACK ? Ditto for other comments.

...

> +               dev_dbg(i2c->dev, "%s: %s %02x\n", __func__,
> +                       action_str[i2c->action], byte);

You already printed action. Anything changed?

> +               dev_dbg(i2c->dev, "%s: %s %02x\n", __func__,
> +                       action_str[i2c->action], msg->buf[i2c->byte_posn]);

Deduplicate this. Perhaps at the end of switch-case print once with
whatever temporary variable value you want to.

...

> +       case MPC_I2C_ACTION_INVALID:
> +       default:

Does the first one deserve loud WARN?
Otherwise, why is it defined at all?

> +               WARN(1, "Unexpected action %d\n", i2c->action);
> +               break;

...

> +static void mpc_i2c_do_intr(struct mpc_i2c *i2c, u8 status)
>  {

> +       spin_lock_irqsave(&i2c->lock, flags);

Why _irqsave?

...

> +               dev_dbg(i2c->dev, "arbiritration lost\n");

arbitration

...

> +       if (i2c->expect_rxack && (status & CSR_RXAK)) {
> +               dev_dbg(i2c->dev, "no RXAK\n");

You see, you have to be consistent in comments and messages.
Either use TXAK/RXAK, or more verbose 'Tx ACK/Rx ACK' everywhere.

...

> +out:

out_unlock:

> +       spin_unlock_irqrestore(&i2c->lock, flags);

...

> +static irqreturn_t mpc_i2c_isr(int irq, void *dev_id)
> +{
> +       struct mpc_i2c *i2c = dev_id;

> +       u8 status = readb(i2c->base + MPC_I2C_SR);

I would split this assignment, so it will be closer to its user.

> +       if (status & CSR_MIF) {
> +               writeb(0, i2c->base + MPC_I2C_SR);
> +               mpc_i2c_do_intr(i2c, status);
> +               return IRQ_HANDLED;
>         }
> +       return IRQ_NONE;
> +}

...

> +       time_left = wait_event_timeout(i2c->waitq, !i2c->block, i2c->adap.timeout);

> +

No need for a blank line here.

> +       if (!time_left)
> +               i2c->rc = -ETIMEDOUT;

> +       else if (time_left < 0)

Redundant 'else'

> +               i2c->rc = time_left;

Can't you return an error code from here, rather than injecting it
somewhere where it doesn't belong to?

>  }

--
With Best Regards,
Andy Shevchenko

  parent reply index

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-13  5:09 [PATCH v3 0/4] i2c: mpc: Refactor to improve responsiveness Chris Packham
2021-04-13  5:09 ` [PATCH v3 1/4] i2c: mpc: use device managed APIs Chris Packham
2021-04-13 12:21   ` Wolfram Sang
2021-04-13 13:31     ` Andy Shevchenko
2021-04-13 13:31       ` Andy Shevchenko
2021-04-13  5:09 ` [PATCH v3 2/4] i2c: mpc: Interrupt driven transfer Chris Packham
2021-04-13 12:22   ` Wolfram Sang
2021-04-13 13:52   ` Andy Shevchenko [this message]
2021-04-13 22:28     ` Chris Packham
2021-04-13 23:23       ` Chris Packham
2021-04-13  5:09 ` [PATCH v3 3/4] i2c: mpc: Remove redundant NULL check Chris Packham
2021-04-13 12:27   ` Wolfram Sang
2021-04-13  5:09 ` [PATCH v3 3/3] MAINTAINERS: Add Chris Packham as FREESCALE MPC I2C maintainer Chris Packham
2021-04-13  5:14   ` Chris Packham
2021-04-13 11:19     ` Andy Shevchenko
2021-04-13  5:09 ` [PATCH v3 4/4] " Chris Packham
2021-04-13 12:27   ` Wolfram Sang

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='CAHp75VfR2zNmstvqCSRC2=0hf2DRV7sMdmy9-TDkO07KHwLjGA@mail.gmail.com' \
    --to=andy.shevchenko@gmail.com \
    --cc=chris.packham@alliedtelesis.co.nz \
    --cc=linux-i2c@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=wsa@kernel.org \
    /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

Linux-i2c Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-i2c/0 linux-i2c/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-i2c linux-i2c/ https://lore.kernel.org/linux-i2c \
		linux-i2c@vger.kernel.org
	public-inbox-index linux-i2c

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-i2c


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git