linux-kernel - Re: [PATCH v3] i2c: exynos5: Init data before registering interrupt handler

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Message-ID: <949c82da-f0dc-4824-ac57-bc86ae42d871@samsung.com>
Date: Thu, 7 Mar 2024 12:41:06 +0100
From: Marek Szyprowski <m.szyprowski@...sung.com>
To: Jesper Nilsson <jesper.nilsson@...s.com>, Andi Shyti
	<andi.shyti@...nel.org>, Krzysztof Kozlowski
	<krzysztof.kozlowski@...aro.org>, Alim Akhtar <alim.akhtar@...sung.com>
Cc: linux-i2c@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel@...s.com
Subject: Re: [PATCH v3] i2c: exynos5: Init data before registering interrupt
 handler

On 05.03.2024 11:50, Jesper Nilsson wrote:
> devm_request_irq() is called before we initialize the "variant"
> member variable from of_device_get_match_data(), so if an interrupt
> is triggered inbetween, we can end up following a NULL pointer
> in the interrupt handler.
>
> This problem was exposed when the I2C controller in question was
> (mis)configured to be used in both secure world and Linux.
>
> That this can happen is also reflected by the existing code that
> clears any pending interrupts from "u-boot or misc causes".
>
> Move the clearing of pending interrupts and the call to
> devm_request_irq() to the end of probe.
>
> Reviewed-by: Andi Shyti <andi.shyti@...nel.org>
> Fixes: 218e1496135e ("i2c: exynos5: add support for HSI2C on Exynos5260 SoC")
> Signed-off-by: Jesper Nilsson <jesper.nilsson@...s.com>
> ---
> Changes in v3:
> - Avoid multiple assignment
> - Link to v2: https://lore.kernel.org/r/20240304-i2c_exynos5-v2-1-7b9c312be719@axis.com
>
> Changes in v2:
> - Use dev_err_probe() instead of open coding it
> - Dropped the return failure if we can't find a match in devicetree
> - Link to v1: https://lore.kernel.org/r/20240304-i2c_exynos5-v1-1-e91c889d2025@axis.com
> ---
>   drivers/i2c/busses/i2c-exynos5.c | 29 +++++++++++++++--------------
>   1 file changed, 15 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-exynos5.c b/drivers/i2c/busses/i2c-exynos5.c
> index 385ef9d9e4d4..8458e22313a7 100644
> --- a/drivers/i2c/busses/i2c-exynos5.c
> +++ b/drivers/i2c/busses/i2c-exynos5.c
> @@ -906,23 +906,9 @@ static int exynos5_i2c_probe(struct platform_device *pdev)
>   	i2c->adap.algo_data = i2c;
>   	i2c->adap.dev.parent = &pdev->dev;
>   
> -	/* Clear pending interrupts from u-boot or misc causes */
> -	exynos5_i2c_clr_pend_irq(i2c);
> -
>   	spin_lock_init(&i2c->lock);
>   	init_completion(&i2c->msg_complete);
>   
> -	i2c->irq = ret = platform_get_irq(pdev, 0);
> -	if (ret < 0)
> -		goto err_clk;
> -
> -	ret = devm_request_irq(&pdev->dev, i2c->irq, exynos5_i2c_irq,
> -			       IRQF_NO_SUSPEND, dev_name(&pdev->dev), i2c);
> -	if (ret != 0) {
> -		dev_err(&pdev->dev, "cannot request HS-I2C IRQ %d\n", i2c->irq);
> -		goto err_clk;
> -	}
> -
>   	i2c->variant = of_device_get_match_data(&pdev->dev);
>   
>   	ret = exynos5_hsi2c_clock_setup(i2c);
> @@ -940,6 +926,21 @@ static int exynos5_i2c_probe(struct platform_device *pdev)
>   	clk_disable(i2c->clk);
>   	clk_disable(i2c->pclk);
>   
> +	/* Clear pending interrupts from u-boot or misc causes */
> +	exynos5_i2c_clr_pend_irq(i2c);

Just above this call the clocks have been disabled, so any access to the 
i2c host registers will result in freeze or external abort (depending on 
the soc/cpu).

To make things worse, this patch moved registering the interrupt handler 
after the i2c_add_adapter() call. This means that all i2c devices that 
will be probbed directly from i2c_add_adapter() won't be able to access 
the i2c bus, as the host controller is still not fully functional that 
time yet.

This breaks today's linux-next on all Exynos5+ platforms. Has anyone 
tested this change?

> +
> +	ret = platform_get_irq(pdev, 0);
> +	if (ret < 0)
> +		goto err_clk;
> +	i2c->irq = ret;
> +
> +	ret = devm_request_irq(&pdev->dev, i2c->irq, exynos5_i2c_irq,
> +			       IRQF_NO_SUSPEND, dev_name(&pdev->dev), i2c);
> +	if (ret != 0) {
> +		dev_err(&pdev->dev, "cannot request HS-I2C IRQ %d\n", i2c->irq);
> +		goto err_clk;
> +	}
> +
>   	return 0;
>   
>    err_clk:
>
Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland