[PATCH 1/3] spi: airoha-snfi: en7523: workaround flash damaging if UART_TXD was short to GND

[Lorenzo Bianconi]

> 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. This will 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.
> 
> 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. Usage of UBI make things even
> worse. Any attempt to access UBI leads to ubi damaging. As result OS loading
> becomes impossible.
> 
> Non-DMA reading is OK.
> 
> This patch detects booting in reserved mode, turn off DMA and print big
> fat warning.
> 
> Signed-off-by: Mikhail Kshevetskiy <mikhail.kshevetskiy at iopsys.eu>
> ---
>  drivers/spi/spi-airoha-snfi.c | 40 ++++++++++++++++++++++++++++++-----
>  1 file changed, 35 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/spi/spi-airoha-snfi.c b/drivers/spi/spi-airoha-snfi.c
> index 8408aee9c06e..0e84a9addfa5 100644
> --- a/drivers/spi/spi-airoha-snfi.c
> +++ b/drivers/spi/spi-airoha-snfi.c
> @@ -1013,6 +1013,11 @@ static const struct spi_controller_mem_ops airoha_snand_mem_ops = {
>  	.dirmap_write = airoha_snand_dirmap_write,
>  };
>  
> +static const struct spi_controller_mem_ops airoha_snand_nodma_mem_ops = {
> +	.supports_op = airoha_snand_supports_op,
> +	.exec_op = airoha_snand_exec_op,
> +};
> +
>  static int airoha_snand_setup(struct spi_device *spi)
>  {
>  	struct airoha_snand_ctrl *as_ctrl;
> @@ -1058,7 +1063,8 @@ static int airoha_snand_probe(struct platform_device *pdev)
>  	struct device *dev = &pdev->dev;
>  	struct spi_controller *ctrl;
>  	void __iomem *base;
> -	int err;
> +	int err, dma_enabled;

here you can use bool for dma_enable:

	bool dma_enable = true;

> +	u32 sfc_strap;
>  
>  	ctrl = devm_spi_alloc_host(dev, sizeof(*as_ctrl));
>  	if (!ctrl)
> @@ -1092,12 +1098,36 @@ static int airoha_snand_probe(struct platform_device *pdev)
>  		return dev_err_probe(dev, PTR_ERR(as_ctrl->spi_clk),
>  				     "unable to get spi clk\n");
>  
> -	err = dma_set_mask(as_ctrl->dev, DMA_BIT_MASK(32));
> -	if (err)
> -		return err;
> +	dma_enabled = 1;
> +	if (device_is_compatible(dev, "airoha,en7523-snand")) {
> +		err = regmap_read(as_ctrl->regmap_ctrl,
> +				  REG_SPI_CTRL_SFC_STRAP, &sfc_strap);
> +		if (err)
> +			return err;
> +
> +		if (!(sfc_strap & 0x04)) {
> +			dma_enabled = 0;

			dma_enable = false;

> +			dev_warn(dev,
> +				"=== WARNING ======================================================\n"

you do not need to add "WARNING here".

> +				"Detected booting in RESERVED mode (UART_TXD was short to GND).\n"
> +				"This mode is known for incorrect DMA reading of some flashes.\n"
> +				"Usage of DMA for flash operations will be disabled to prevent data\n"
> +				"damage. Unplug your serial console and power cycle the board\n"
> +				"to boot with full performance.\n"
> +				"==================================================================\n");
> +		}
> +	}
> +
> +	if (dma_enabled) {
> +		err = dma_set_mask(as_ctrl->dev, DMA_BIT_MASK(32));
> +		if (err)
> +			return err;
> +	}
>  
>  	ctrl->num_chipselect = 2;
> -	ctrl->mem_ops = &airoha_snand_mem_ops;
> +	ctrl->mem_ops = dma_enabled ?
> +				&airoha_snand_mem_ops :
> +				&airoha_snand_nodma_mem_ops;

nit: no need to add a new-line here:

	ctrl->mem_ops = dma_enabled ? &airoha_snand_mem_ops
				    : &airoha_snand_nodma_mem_ops;


Regards,
Lorenzo

>  	ctrl->bits_per_word_mask = SPI_BPW_MASK(8);
>  	ctrl->mode_bits = SPI_RX_DUAL;
>  	ctrl->setup = airoha_snand_setup;
> -- 
> 2.51.0
> 
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