linux-kernel - Re: [PATCH v4 1/3] spi: airoha-snfi: en7523: workaround flash damaging if UART

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Message-ID: <aSWBacH8N5NWO8oV@smile.fi.intel.com>
Date: Tue, 25 Nov 2025 12:14:01 +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 v4 1/3] spi: airoha-snfi: en7523: workaround flash
 damaging if UART_TXD was short to GND

On Tue, Nov 25, 2025 at 01:04:12PM +0300, Mikhail Kshevetskiy wrote:
> On 11/25/25 10:18, Andy Shevchenko wrote:
> > On Tue, Nov 25, 2025 at 05:10:49AM +0300, Mikhail Kshevetskiy wrote:
> >> Airoha EN7523 specific bug
> >> --------------------------
> >> We found that some serial console may pull TX line to GROUND during board
> >> boot time. Airoha uses TX line as one of it's BOOT pins.
> > I know the term bootstrap, what does BOOT mean?
> 
> yes, it's bootstrap pin

Then use that term.

> >> On the EN7523 SoC this may lead to booting in RESERVED boot mode.
> >>
> >> It was found that some flashes operates incorrectly in RESERVED mode.
> >> Micron and Skyhigh flashes are definitely affected by the issue,
> >> Winbond flashes are NOT affected.
> > NOT --> not
> will fix

> >> Details:
> >> --------
> >> DMA reading of odd pages on affected flashes operates incorrectly. Page
> >> reading offset (start of the page) on hardware level is replaced by 0x10.
> >> Thus results in incorrect data reading. As result OS loading becomes
> >> impossible.
> >>
> >> Usage of UBI make things even worse. On attaching, UBI will detects
> >> corruptions (because of wrong reading of odd pages) and will try to
> >> recover. For recovering UBI will erase and write 'damaged' blocks with
> >> a valid information. This will destroy all UBI data.
> >>
> >> Non-DMA reading is OK.
> >>
> >> This patch detects booting in reserved mode, turn off DMA and print big
> >> fat warning.

...

> >> -	err = dma_set_mask(as_ctrl->dev, DMA_BIT_MASK(32));
> >> -	if (err)
> >> -		return err;
> >> +	if (dma_enable) {
> >> +		err = dma_set_mask(as_ctrl->dev, DMA_BIT_MASK(32));
> >> +		if (err)
> >> +			return err;
> >> +	}
> > Why do you need this to be conditional? The settings of DMA mask should not
> > affect the (in)ability of the device to perform DMA. I.o.w. it should not
> > influence PIO mode. Can you confirm this?
> >
> no any particular reason, just see no sense to set mask if dma will not
> be used

So, this is an unneeded churn in the patch. Device is [still] capable of DMA?
Yes. Set the mask. The DMA/PIO choice is done on the upper layer (as you do it
via ops).

-- 
With Best Regards,
Andy Shevchenko