On Mon, Feb 01, 2021 at 03:30:43PM +0800, zhangqiumiao1@xxxxxxxxxx wrote: > From: Qiumiao Zhang <zhangqiumiao1@xxxxxxxxxx> > > make pl011 serial port support 485 mode full duplex communication > > Signed-off-by: Qiumiao Zhang <zhangqiumiao1@xxxxxxxxxx> > --- > Changes in v4: > -Add a bound to the loop in pl011_stop_tx > -Remove extra curly braces in pl011_stop_tx > > Changes in v3: > -Fix busy loop forever in pl011_tx_empty > -Move the definition of cr into uart_amba_port > -Run checkpatch with no error or warning > > Changes in v2: > -Fix two compilation errors > > drivers/tty/serial/amba-pl011.c | 38 ++++++++++++++++++++++++++++++++++++++ > 1 file changed, 38 insertions(+) > > diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c > index c255476..026add3 100644 > --- a/drivers/tty/serial/amba-pl011.c > +++ b/drivers/tty/serial/amba-pl011.c > @@ -44,6 +44,7 @@ > > #include "amba-pl011.h" > > +#define ISEMPTY 1 > #define UART_NR 14 > > #define SERIAL_AMBA_MAJOR 204 > @@ -264,6 +265,7 @@ struct uart_amba_port { > unsigned int fifosize; /* vendor-specific */ > unsigned int old_cr; /* state during shutdown */ > unsigned int fixed_baud; /* vendor-set fixed baud rate */ > + unsigned int cr; > char type[12]; > #ifdef CONFIG_DMA_ENGINE > /* DMA stuff */ > @@ -1284,14 +1286,33 @@ static inline bool pl011_dma_rx_running(struct uart_amba_port *uap) > #define pl011_dma_flush_buffer NULL > #endif > > +static unsigned int pl011_tx_empty(struct uart_port *port); > + > static void pl011_stop_tx(struct uart_port *port) > { > + unsigned int count = 1000000; /* 1s */ 1 second of what? > struct uart_amba_port *uap = > container_of(port, struct uart_amba_port, port); > > uap->im &= ~UART011_TXIM; > pl011_write(uap->im, uap, REG_IMSC); > pl011_dma_tx_stop(uap); > + if (port->rs485.flags & SER_RS485_ENABLED) { > + while(pl011_tx_empty(port) != ISEMPTY && count) { > + count--; > + cpu_relax(); > + udelay(1); Why relax and delay? And always run checkpatch on your change before sending it out next time. thanks, greg k-h