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Message-ID: <a46e91ad-8cbc-4a4d-9268-f27906077e68@fivetechno.de>
Date: Thu, 7 Mar 2024 14:29:31 +0100
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Subject: Re: [PATCH v3] i2c: exynos5: Init data before registering interrupt
 handler
To: Marek Szyprowski <m.szyprowski@samsung.com>,
        Jesper Nilsson <jesper.nilsson@axis.com>,
        Andi Shyti
 <andi.shyti@kernel.org>,
        Krzysztof Kozlowski
 <krzysztof.kozlowski@linaro.org>,
        Alim Akhtar <alim.akhtar@samsung.com>
Cc: linux-i2c@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org,
        kernel@axis.com
References: <CGME20240305105548eucas1p110f1ecf1570ff69a618ca86297eeba89@eucas1p1.samsung.com>
 <20240305-i2c_exynos5-v3-1-17a749688806@axis.com>
 <949c82da-f0dc-4824-ac57-bc86ae42d871@samsung.com>
From: Markus Reichl <m.reichl@fivetechno.de>
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In-Reply-To: <949c82da-f0dc-4824-ac57-bc86ae42d871@samsung.com>
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Hi Marek,

Am 07.03.24 um 12:41 schrieb Marek Szyprowski:
> 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@kernel.org>
> > Fixes: 218e1496135e ("i2c: exynos5: add support for HSI2C on Exynos5260 SoC")
> > Signed-off-by: Jesper Nilsson <jesper.nilsson@axis.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?
Tested this patch on top of stable 6.7.9, breaks booting odroid-xu4.

Gruß,
--
Markus

>
> > +
> > +	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