On Sun, Dec 04, 2022 at 01:36:55PM +0100, Pali Rohár wrote: > U-Boot serial code already handles -EAGAIN value from getc and putc > callbacks. So change drivers code to return -EAGAIN when HW is busy instead > of doing its own busy loop and waiting until HW is ready. > > Signed-off-by: Pali Rohár <p...@kernel.org> > Reviewed-by: Simon Glass <s...@chromium.org> > Reviewed-by: Stefan Roese <s...@denx.de> [snip] > diff --git a/drivers/serial/serial_lpuart.c b/drivers/serial/serial_lpuart.c > index ff576da516d4..d7259d531b55 100644 > --- a/drivers/serial/serial_lpuart.c > +++ b/drivers/serial/serial_lpuart.c > @@ -168,8 +168,8 @@ static void _lpuart_serial_setbrg(struct udevice *dev, > static int _lpuart_serial_getc(struct lpuart_serial_plat *plat) > { > struct lpuart_fsl *base = plat->reg; > - while (!(__raw_readb(&base->us1) & (US1_RDRF | US1_OR))) > - schedule(); > + if (!(__raw_readb(&base->us1) & (US1_RDRF | US1_OR))) > + return -EAGAIN; > > barrier(); > > @@ -181,8 +181,8 @@ static void _lpuart_serial_putc(struct lpuart_serial_plat > *plat, > { > struct lpuart_fsl *base = plat->reg; > > - while (!(__raw_readb(&base->us1) & US1_TDRE)) > - schedule(); > + if (!(__raw_readb(&base->us1) & US1_TDRE)) > + return -EAGAIN; > > __raw_writeb(c, &base->ud); > }
This is non-trivially not right for this driver. ->putc here is set to lpuart_serial_putc which calls _lpuart_serial_putc OR _lpuart32_serial_putc, so there's the lpuart32 cases to address, and then lpuart_serial_putc needs to just return whatever one it called rather than always returning 0. -- Tom
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