linux-kernel - Re: [PATCH] i2c: at91: support atomic write xfer

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Message-ID: <9924dd54-dd8b-d130-9607-2bbbc65675d5@gmail.com>
Date:   Sun, 15 Mar 2020 23:46:33 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        Ludovic Desroches <ludovic.desroches@...rochip.com>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c: at91: support atomic write xfer

15.03.2020 21:27, Michał Mirosław пишет:
> Implement basic support for atomic write - enough to get a simple
> write to PMIC on shutdown. Only for chips having ALT_CMD register,
> eg. SAMA5D2.
> 
> Signed-off-by: Michał Mirosław <mirq-linux@...e.qmqm.pl>
> ---

Hello Michał,

...
> +	ret = pm_runtime_get_sync(dev->dev);
> +	if (ret < 0)
> +		goto out;

Runtime PM can't be used while interrupts are disabled, unless
pm_runtime_irq_safe() is used and driver's RPM callback is IRQ-safe.

...
> +	timeout = jiffies + (2 + msg->len) * HZ/1000;
> +	for (;;) {
> +		stat = at91_twi_read(dev, AT91_TWI_SR);
> +		if (stat & AT91_TWI_TXCOMP)
> +			break;
> +		if (time_after(jiffies, timeout)) {
> +			ret = -ETIMEDOUT;
> +			goto out;
> +		}
> +		udelay(100);
> +	}

Jiffies can't be used with the disabled interrupts because jiffies are
updated by timer's interrupt.

Either ktime() API or iterator-based loop should be used.