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spi: dw: fix first spi transfer with dma always fallback to PIO

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Even with proper dma engine support, the first spi transfer always
fallback to PIO, the reason is the dws->n_bytes is 0 after
initialization, so the dw_spi_can_dma() calling from __spi_map_msg()
return false, thus both tx_sg_mapped and rx_sg_mapped are false, so
for the first spi transfer, the spi_xfer_is_dma_mapped() reports false
thus fallback to PIO.

Although this brings no harm, we can simply fix this issue by
calcuating the "n_bytes" from xfer->bits_per_word.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Link: https://patch.msgid.link/20260615044039.9750-2-jszhang@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Jisheng Zhang 2026-06-15 12:40:35 +08:00 committed by Mark Brown
parent c1bab046d4
commit d322d820e0
No known key found for this signature in database
GPG Key ID: 24D68B725D5487D0
1 changed files with 2 additions and 1 deletions
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3
drivers/spi/spi-dw-dma.c
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@ -247,11 +247,12 @@ static bool dw_spi_can_dma(struct spi_controller *ctlr,
{
struct dw_spi *dws = spi_controller_get_devdata(ctlr);
enum dma_slave_buswidth dma_bus_width;
u8 n_bytes = roundup_pow_of_two(BITS_TO_BYTES(xfer->bits_per_word));
if (xfer->len <= dws->fifo_len)
return false;
dma_bus_width = dw_spi_dma_convert_width(dws->n_bytes);
dma_bus_width = dw_spi_dma_convert_width(n_bytes);
return dws->dma_addr_widths & BIT(dma_bus_width);
}