linux-kernel - Re: [PATCH v2 1/7] i2c: stm32f7: perform most of irq job in threaded handler

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20231208200425.zli2j6b4lt4shasn@zenone.zhora.eu>
Date:   Fri, 8 Dec 2023 21:04:25 +0100
From:   Andi Shyti <andi.shyti@...nel.org>
To:     Alain Volmat <alain.volmat@...s.st.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Pierre-Yves MORDRET <pierre-yves.mordret@...s.st.com>,
        Conor Dooley <conor@...nel.org>, Rob Herring <robh@...nel.org>,
        linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/7] i2c: stm32f7: perform most of irq job in threaded
 handler

Hi Alain,

On Fri, Dec 08, 2023 at 05:47:10PM +0100, Alain Volmat wrote:
> The irq handling is currently split between the irq handler
> and the threaded irq handler.  Some of the handling (such as
> dma related stuffs) done within the irq handler might sleep or
> take some time leading to issues if the kernel is built with
> realtime constraints.  In order to fix that, perform an overall
> rework to perform most of the job within the threaded handler
> and only keep fifo access in the non threaded handler.
> 
> Signed-off-by: Alain Volmat <alain.volmat@...s.st.com>

quite a difficult review because this git diff algorithm makes it
difficult to read throuhg.

But it looks like just a copy paste from to
stm32f7_i2c_isr_event() to stm32f7_i2c_isr_event_thread() of the
STM32F7_I2C_ISR_NACKF, STM32F7_I2C_ISR_STOPF, STM32F7_I2C_ISR_TC
and STM32F7_I2C_ISR_TCR.

[...]

> +static irqreturn_t stm32f7_i2c_isr_event_thread(int irq, void *data)
> +{
> +	struct stm32f7_i2c_dev *i2c_dev = data;
> +	struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
> +	struct stm32_i2c_dma *dma = i2c_dev->dma;
> +	void __iomem *base = i2c_dev->base;
> +	u32 status, mask;
> +	int ret;
> +
> +	if (!i2c_dev->master_mode)
> +		return stm32f7_i2c_slave_isr_event(i2c_dev);
> +
> +	status = readl_relaxed(i2c_dev->base + STM32F7_I2C_ISR);

looks to me like this readl_relaxed is read too many times during
the whole irq handling.

Reviewed-by: Andi Shyti <andi.shyti@...nel.org>

Thanks,
Andi