linux-kernel - Re: [PATCH v5 1/3] spi: airoha-snfi: en7523: workaround flash damaging if UART

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Message-ID: <aSYQgZR1YoVQkbxC@smile.fi.intel.com>
Date: Tue, 25 Nov 2025 22:24:33 +0200
From: Andy Shevchenko <andriy.shevchenko@...el.com>
To: Mikhail Kshevetskiy <mikhail.kshevetskiy@...sys.eu>
Cc: Lorenzo Bianconi <lorenzo@...nel.org>, Ray Liu <ray.liu@...oha.com>,
	Mark Brown <broonie@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	Andy Shevchenko <andy@...nel.org>,
	linux-arm-kernel@...ts.infradead.org, linux-spi@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mediatek@...ts.infradead.org,
	Andreas Gnau <andreas.gnau@...sys.eu>
Subject: Re: [PATCH v5 1/3] spi: airoha-snfi: en7523: workaround flash
 damaging if UART_TXD was short to GND

On Tue, Nov 25, 2025 at 10:16:33PM +0300, Mikhail Kshevetskiy wrote:

...

> +			dev_warn(dev, "Detected booting in RESERVED mode (UART_TXD was short to GND).\n");
> +			dev_warn(dev, "This mode is known for incorrect DMA reading of some flashes.\n");
> +			dev_warn(dev, "Usage of DMA for flash operations will be disabled to prevent data\n");
> +			dev_warn(dev, "damage. Unplug your serial console and power cycle the board\n");
> +			dev_warn(dev, "to boot with full performance.\n");

One non-critical remark (for the future), the '\n' in the string literals when
we print messages has two meanings:
 - (obviously) new line
 - (seems not so obvious for people) flush the line to the output device

Due to the second property the messages might be interleaved with the other
messages (assuming SMP machine actively doing and printing something), hence
your messages might be split with other and imagine the user who gets in the
middle of the text something like

"Usage of DMA for flash operations will be disabled to prevent data"

The first thought will be "what the heck does this mean?"

TL;DR: place '\n' with a care in the messages to print not only here,
but in general.

-- 
With Best Regards,
Andy Shevchenko