linux-kernel - Re: [PATCH v4 2/5] gpio: Add support for Intel LJCA USB GPIO driver

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Date:   Thu, 9 Mar 2023 14:40:10 +0100
From:   Oliver Neukum <oneukum@...e.com>
To:     Ye Xiang <xiang.ye@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Matthias Kaehlcke <mka@...omium.org>,
        Lee Jones <lee@...nel.org>, Wolfram Sang <wsa@...nel.org>,
        Tyrone Ting <kfting@...oton.com>,
        Mark Brown <broonie@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>, linux-usb@...r.kernel.org,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-spi@...r.kernel.org, linux-gpio@...r.kernel.org
Cc:     srinivas.pandruvada@...el.com, heikki.krogerus@...ux.intel.com,
        andriy.shevchenko@...ux.intel.com, sakari.ailus@...ux.intel.com,
        zhifeng.wang@...el.com, wentong.wu@...el.com, lixu.zhang@...el.com
Subject: Re: [PATCH v4 2/5] gpio: Add support for Intel LJCA USB GPIO driver



On 09.03.23 08:10, Ye Xiang wrote:

> +#define LJCA_GPIO_BUF_SIZE 60
> +struct ljca_gpio_dev {
> +	struct platform_device *pdev;
> +	struct gpio_chip gc;
> +	struct ljca_gpio_info *gpio_info;
> +	DECLARE_BITMAP(unmasked_irqs, LJCA_MAX_GPIO_NUM);
> +	DECLARE_BITMAP(enabled_irqs, LJCA_MAX_GPIO_NUM);
> +	DECLARE_BITMAP(reenable_irqs, LJCA_MAX_GPIO_NUM);
> +	u8 *connect_mode;
> +	/* mutex to protect irq bus */
> +	struct mutex irq_lock;
> +	struct work_struct work;
> +	/* lock to protect package transfer to Hardware */
> +	struct mutex trans_lock;
> +
> +	u8 obuf[LJCA_GPIO_BUF_SIZE];
> +	u8 ibuf[LJCA_GPIO_BUF_SIZE];

And here we have a violation of DMA coherency rules.
Basically you cannot embed buffers into other data structures
if they can be subject to DMA.




> +static int ljca_gpio_remove(struct platform_device *pdev)
> +{
> +	struct ljca_gpio_dev *ljca_gpio = platform_get_drvdata(pdev);
> +
> +	gpiochip_remove(&ljca_gpio->gc);
> +	ljca_unregister_event_cb(ljca_gpio->gpio_info->ljca);
> +	mutex_destroy(&ljca_gpio->irq_lock);
> +	mutex_destroy(&ljca_gpio->trans_lock);

At this time, what has made sure that no work is scheduled?

> +	return 0;
> +}

	Regards
		Oliver