On Friday 15 January 2021 15:50:46 Stefan Roese wrote: > On 14.01.21 15:46, Pali Rohár wrote: > > To check if some output characters are waiting either in Transmitter > > Holding Register or Transmitter Shift Register we need to look at > > TX_EMPTY bit of UART Status Register. > > > > Signed-off-by: Pali Rohár <p...@kernel.org> > > Reviewed-by: Stefan Roese <s...@denx.de> > > BTW: How did you detect this issue?
During debugging both TF-A and linux kernel as they were eating characters sent via A3720 UART. Details are in kernel and TF-A patches: https://lore.kernel.org/linux-serial/20201223191931.18343-1-p...@kernel.org/ https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/7734 I have not spotted this issue in U-Boot (only in TF-A and kernel), but I decided to look also at the U-Boot A3720 UART implementation... And find out that it is incomplete too, ignoring 'bool input' function argument. > Thanks, > Stefan > > > --- > > drivers/serial/serial_mvebu_a3700.c | 10 ++++++++-- > > 1 file changed, 8 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/serial/serial_mvebu_a3700.c > > b/drivers/serial/serial_mvebu_a3700.c > > index fb43f88eaf..909901c9f0 100644 > > --- a/drivers/serial/serial_mvebu_a3700.c > > +++ b/drivers/serial/serial_mvebu_a3700.c > > @@ -23,6 +23,7 @@ struct mvebu_platdata { > > #define UART_POSSR_REG 0x14 > > #define UART_STATUS_RX_RDY 0x10 > > +#define UART_STATUS_TX_EMPTY 0x40 > > #define UART_STATUS_TXFIFO_FULL 0x800 > > #define UART_CTRL_RXFIFO_RESET 0x4000 > > @@ -59,8 +60,13 @@ static int mvebu_serial_pending(struct udevice *dev, > > bool input) > > struct mvebu_platdata *plat = dev_get_platdata(dev); > > void __iomem *base = plat->base; > > - if (readl(base + UART_STATUS_REG) & UART_STATUS_RX_RDY) > > - return 1; > > + if (input) { > > + if (readl(base + UART_STATUS_REG) & UART_STATUS_RX_RDY) > > + return 1; > > + } else { > > + if (!(readl(base + UART_STATUS_REG) & UART_STATUS_TX_EMPTY)) > > + return 1; > > + } > > return 0; > > } > > > > > Viele Grüße, > Stefan > > -- > DENX Software Engineering GmbH, Managing Director: Wolfgang Denk > HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany > Phone: (+49)-8142-66989-51 Fax: (+49)-8142-66989-80 Email: s...@denx.de
