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When a > client requests a transfer where the length is not evenly divisible by > the configured max burst size, the DMA hangs with partial burst at > the end. > > Fix this by reducing the burst size to the largest power-of-2 value > that evenly divides the transfer length. For example, a 40-byte > transfer with a 16-byte max burst will now use an 8-byte burst > (40 / 8 = 5 complete bursts) instead of causing a hang. > > This issue was observed with the PL011 UART driver where TX DMA > transfers of arbitrary lengths were stuck. > > Fixes: ee17028009d4 ("dmaengine: tegra: Add tegra gpcdma driver") > Cc: stable@vger.kernel.org > Signed-off-by: Kartik Rajput > Reviewed-by: Frank Li > --- > drivers/dma/tegra186-gpc-dma.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/drivers/dma/tegra186-gpc-dma.c b/drivers/dma/tegra186-gpc-dma.c > index 5948fbf32c21..0aa3a02b2277 100644 > --- a/drivers/dma/tegra186-gpc-dma.c > +++ b/drivers/dma/tegra186-gpc-dma.c > @@ -825,6 +825,13 @@ static unsigned int get_burst_size(struct tegra_dma_channel *tdc, > * len to calculate the optimum burst size > */ > burst_byte = burst_size ? burst_size * slave_bw : len; > + > + /* > + * Find the largest burst size that evenly divides the transfer length. > + * The hardware requires the transfer length to be a multiple of the > + * burst size - partial bursts are not supported. > + */ > + burst_byte = min(burst_byte, 1U << __ffs(len)); > burst_mmio_width = burst_byte / 4; > > if (burst_mmio_width < TEGRA_GPCDMA_MMIOSEQ_BURST_MIN) Reviewed-by: Jon Hunter Thanks Jon -- nvpublic