| Message ID | 20210520021334.497341-1-andrew@aj.id.au |
|---|---|
| Headers | show |
| Series | serial: 8250: Mitigate Tx stall risk for Aspeed VUARTs | expand |
On 20. 05. 21, 4:13, Andrew Jeffery wrote: > BIT(x) improves readability and safety with respect to shifts. > > Signed-off-by: Andrew Jeffery <andrew@aj.id.au> Reviewed-by: Jiri Slaby <jirislaby@kernel.org> > --- > drivers/tty/serial/8250/8250.h | 33 +++++++++++++++++---------------- > 1 file changed, 17 insertions(+), 16 deletions(-) > > diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h > index 34aa2714f3c9..6473361525d1 100644 > --- a/drivers/tty/serial/8250/8250.h > +++ b/drivers/tty/serial/8250/8250.h > @@ -7,6 +7,7 @@ > * Copyright (C) 2001 Russell King. > */ > > +#include <linux/bits.h> > #include <linux/serial_8250.h> > #include <linux/serial_reg.h> > #include <linux/dmaengine.h> > @@ -70,25 +71,25 @@ struct serial8250_config { > unsigned int flags; > }; > > -#define UART_CAP_FIFO (1 << 8) /* UART has FIFO */ > -#define UART_CAP_EFR (1 << 9) /* UART has EFR */ > -#define UART_CAP_SLEEP (1 << 10) /* UART has IER sleep */ > -#define UART_CAP_AFE (1 << 11) /* MCR-based hw flow control */ > -#define UART_CAP_UUE (1 << 12) /* UART needs IER bit 6 set (Xscale) */ > -#define UART_CAP_RTOIE (1 << 13) /* UART needs IER bit 4 set (Xscale, Tegra) */ > -#define UART_CAP_HFIFO (1 << 14) /* UART has a "hidden" FIFO */ > -#define UART_CAP_RPM (1 << 15) /* Runtime PM is active while idle */ > -#define UART_CAP_IRDA (1 << 16) /* UART supports IrDA line discipline */ > -#define UART_CAP_MINI (1 << 17) /* Mini UART on BCM283X family lacks: > +#define UART_CAP_FIFO BIT(8) /* UART has FIFO */ > +#define UART_CAP_EFR BIT(9) /* UART has EFR */ > +#define UART_CAP_SLEEP BIT(10) /* UART has IER sleep */ > +#define UART_CAP_AFE BIT(11) /* MCR-based hw flow control */ > +#define UART_CAP_UUE BIT(12) /* UART needs IER bit 6 set (Xscale) */ > +#define UART_CAP_RTOIE BIT(13) /* UART needs IER bit 4 set (Xscale, Tegra) */ > +#define UART_CAP_HFIFO BIT(14) /* UART has a "hidden" FIFO */ > +#define UART_CAP_RPM BIT(15) /* Runtime PM is active while idle */ > +#define UART_CAP_IRDA BIT(16) /* UART supports IrDA line discipline */ > +#define UART_CAP_MINI BIT(17) /* Mini UART on BCM283X family lacks: > * STOP PARITY EPAR SPAR WLEN5 WLEN6 > */ > > -#define UART_BUG_QUOT (1 << 0) /* UART has buggy quot LSB */ > -#define UART_BUG_TXEN (1 << 1) /* UART has buggy TX IIR status */ > -#define UART_BUG_NOMSR (1 << 2) /* UART has buggy MSR status bits (Au1x00) */ > -#define UART_BUG_THRE (1 << 3) /* UART has buggy THRE reassertion */ > -#define UART_BUG_PARITY (1 << 4) /* UART mishandles parity if FIFO enabled */ > -#define UART_BUG_TXRACE (1 << 5) /* UART Tx fails to set remote DR */ > +#define UART_BUG_QUOT BIT(0) /* UART has buggy quot LSB */ > +#define UART_BUG_TXEN BIT(1) /* UART has buggy TX IIR status */ > +#define UART_BUG_NOMSR BIT(2) /* UART has buggy MSR status bits (Au1x00) */ > +#define UART_BUG_THRE BIT(3) /* UART has buggy THRE reassertion */ > +#define UART_BUG_PARITY BIT(4) /* UART mishandles parity if FIFO enabled */ > +#define UART_BUG_TXRACE BIT(5) /* UART Tx fails to set remote DR */ > > > #ifdef CONFIG_SERIAL_8250_SHARE_IRQ >
Hello, Briefly, the series works around a hardware race condition in the Tx path for Aspeed virtual UARTs. A write burst to THR on the APB interface may provoke a transfer stall where LSR[DR] on the LPC interface remains clear despite the presence of data in the Rx FIFO. v3 addresses comments from Jiri on v2. v2 can be found here: https://lore.kernel.org/lkml/20210519000704.3661773-1-andrew@aj.id.au/ The documentation patch that fell out of the discussion of patch 2 of v2 can be found here: https://lore.kernel.org/lkml/20210520015704.489737-1-andrew@aj.id.au/T/#u Please review! Andrew Andrew Jeffery (2): serial: 8250: Add UART_BUG_TXRACE workaround for Aspeed VUART serial: 8250: Use BIT(x) for UART_{CAP,BUG}_* drivers/tty/serial/8250/8250.h | 32 +++++++++++---------- drivers/tty/serial/8250/8250_aspeed_vuart.c | 1 + drivers/tty/serial/8250/8250_port.c | 12 ++++++++ 3 files changed, 30 insertions(+), 15 deletions(-)