From: Kongyang Liu seashell11234455@gmail.com
The loop used to calculate HBstLen for extern DMA mode does not produce the correct result according to the datasheet [1]. Replacing that loop with a direct calculation using LOG2 to correctly assign the burst length in the GAHBCFG register for external DMA mode.
[1] https://rockchip.fr/RK312X%20TRM/chapter-26-usb-otg-2-0.pdf#page=24
Signed-off-by: Kongyang Liu seashell11234455@gmail.com Reviewed-by: Marek Vasut marex@denx.de Tested-by: Peter Robinson pbrobinson@gmail.com Reviewed-by: Mattijs Korpershoek mkorpershoek@baylibre.com Signed-off-by: Junhui Liu junhui.liu@pigmoral.tech
--- Additionally, the boards I have only use internal DMA mode, and it’s unclear which chips employ external DMA. The testing was performed by comparing against the datasheet, and the results are shown in [2].
[2] https://gist.github.com/Judehahh/34530da390b58728102778406e602cb1 --- drivers/usb/host/dwc2.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/drivers/usb/host/dwc2.c b/drivers/usb/host/dwc2.c index 609de18faa3abc5f4ecb0c23cf3590966bad7992..954650d856a4f2e95d74e1b5716c0ebe83fa9ba8 100644 --- a/drivers/usb/host/dwc2.c +++ b/drivers/usb/host/dwc2.c @@ -448,11 +448,8 @@ static void dwc_otg_core_init(struct udevice *dev) case DWC2_HWCFG2_ARCHITECTURE_SLAVE_ONLY: break; case DWC2_HWCFG2_ARCHITECTURE_EXT_DMA: - while (brst_sz > 1) { - ahbcfg |= ahbcfg + (1 << DWC2_GAHBCFG_HBURSTLEN_OFFSET); - ahbcfg &= DWC2_GAHBCFG_HBURSTLEN_MASK; - brst_sz >>= 1; - } + ahbcfg |= (LOG2(brst_sz >> 1) << DWC2_GAHBCFG_HBURSTLEN_OFFSET) & + DWC2_GAHBCFG_HBURSTLEN_MASK;
#ifdef DWC2_DMA_ENABLE ahbcfg |= DWC2_GAHBCFG_DMAENABLE;