Re: [PATCH v3 8/9] spi: dw: Use dma_slave_caps bus width helpers

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] `dw_spi_can_dma()` evaluates DMA capability using stale `dws->n_bytes` state from a previous transfer, leading to invalid DMA configurations.
--

commit a1e1fa79562141ff2997ca919b2572914bd4eb82
Author: Nuno Sá <nuno.sa@analog.com>

spi: dw: Use dma_slave_caps bus width helpers

Store the common TX destination and RX source bus widths in a
driver-owned DMA bus width bitmap and populate it through the
dma_slave_caps helper.

> diff --git a/drivers/spi/spi-dw-dma.c b/drivers/spi/spi-dw-dma.c
> index fe726b9b1780d..bbd7ee884d0ec 100644
> --- a/drivers/spi/spi-dw-dma.c
> +++ b/drivers/spi/spi-dw-dma.c
[ ... ]
> @@ -253,7 +255,7 @@ static bool dw_spi_can_dma(struct spi_controller *ctlr,
>  
>  	dma_bus_width = dw_spi_dma_convert_width(dws->n_bytes);
>  
> -	return dws->dma_addr_widths & BIT(dma_bus_width);
> +	return dma_bus_width_test(dws->dma_bus_widths, dma_bus_width);
>  }

[Severity: High]
This is a pre-existing issue, but does dw_spi_can_dma() evaluate DMA capability
using stale dws->n_bytes state from a previous transfer?

It appears spi_map_msg() invokes dw_spi_can_dma() before any transfer in the
message is executed. When dw_spi_can_dma() reads dws->n_bytes to determine the
DMA bus width, it gets the state from the last executed transfer. 

The state is only updated later when the transfer actually starts:

drivers/spi/spi-dw-core.c:dw_spi_transfer_one() {
    ...
    dws->n_bytes = spi_bpw_to_bytes(transfer->bits_per_word);
    ...
}

If a SPI message contains transfers with different bits_per_word, or if the
current message differs from the previous one, can_dma() might incorrectly
return true for a transfer that requires an unsupported DMA bus width. This
could lead to dmaengine_slave_config() failures or DMA hardware malfunctions
and data corruption.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260831-dmaengine-support-wider-dma-masks-v3-0-507d97496f2d@analog.com?part=8