Re: [PATCH v7 04/16] mtd: rawnand: sunxi: drain interrupts before reusing the completion

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: James Hilliard <james.hilliard1@gmail.com>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>,
	Richard Weinberger <richard@nod.at>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	Clark Williams <clrkwllms@kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Chen-Yu Tsai <wens@kernel.org>,
	Jernej Skrabec <jernej.skrabec@gmail.com>,
	Samuel Holland <samuel@sholland.org>,
	Maxime Ripard <mripard@kernel.org>,
	Richard Genoud <richard.genoud@bootlin.com>,
	Boris Brezillon <bbrezillon@kernel.org>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Brian Norris <computersforpeace@gmail.com>,
	linux-mtd@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org,
	linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org,
	linux-rt-devel@lists.linux.dev, devicetree@vger.kernel.org
Subject: Re: [PATCH v7 04/16] mtd: rawnand: sunxi: drain interrupts before reusing the completion
Date: Thu, 15 Oct 2026 09:19:43 +0200	[thread overview]
Message-ID: <20261015071943.7OihPadq@linutronix.de> (raw)
In-Reply-To: <20261014-submit-sunxi-nand-vendor-oob-layout-v1-v7-4-5d3fc6ad2da1@gmail.com>

On 2026-10-14 19:33:51 [-0600], James Hilliard wrote:
> --- a/drivers/mtd/nand/raw/sunxi_nand.c
> +++ b/drivers/mtd/nand/raw/sunxi_nand.c
> @@ -454,16 +457,19 @@ static int sunxi_nfc_wait_events(struct sunxi_nfc *nfc, u32 events,
>  		timeout_ms = NFC_DEFAULT_TIMEOUT_MS;
>  
>  	if (!use_polling) {
> -		init_completion(&nfc->complete);
> +		reinit_completion(&nfc->complete);
>  
>  		writel(events, nfc->regs + NFC_REG_INT);
>  
>  		ret = wait_for_completion_timeout(&nfc->complete,
>  						msecs_to_jiffies(timeout_ms));
> -		if (!ret)
> +		if (!ret) {
> +			/* Drain the handler before it can restore an old IRQ mask. */
> +			disable_irq(nfc->irq);
>  			ret = -ETIMEDOUT;
> -		else
> +		} else {
>  			ret = 0;
> +		}
>  
>  		writel(0, nfc->regs + NFC_REG_INT);
>  	} else {
> @@ -476,6 +482,12 @@ static int sunxi_nfc_wait_events(struct sunxi_nfc *nfc, u32 events,
>  
>  	writel(events & NFC_INT_MASK, nfc->regs + NFC_REG_ST);
>  
> +	if (!use_polling && ret) {
> +		/* Flush the mask and acknowledgment before re-enabling the IRQ. */
> +		readl(nfc->regs + NFC_REG_INT);
> +		enable_irq(nfc->irq);

Shouldn't you re-read NFC_REG_ST, checking if the event became true even
in the case of a timeout?
Say the interrupt wake the thread but the thread never had a chance
to run. The timer (on another CPU) had a chance to run and did wake this
thread. Checking the event in the timeout case would help to prevent
that.

> +	}
> +
>  	if (ret)
>  		dev_err(nfc->dev, "wait interrupt timedout\n");
>  

Sebastian

______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/