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

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Message-ID: <13321124-6b45-479c-a73d-1d9ec9e96f05@iopsys.eu>
Date: Tue, 25 Nov 2025 17:20:44 +0300
From: Mikhail Kshevetskiy <mikhail.kshevetskiy@...sys.eu>
To: Andy Shevchenko <andriy.shevchenko@...el.com>
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 11/25/25 13:14, Andy Shevchenko wrote:
> 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.
> ...

could you clarify what's wrong here?


>
>>>> -	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).
>