Hi Heinrich, On Wed, Dec 31, 2025 at 01:25:10PM +0100, Heinrich Schuchardt wrote: > On 12/30/25 17:01, Kuan-Wei Chiu wrote: > > Add support for the Google Goldfish TTY serial device. This virtual > > device is commonly used in QEMU virtual machines (such as the m68k > > virt machine) and Android emulators. > > > > The driver implements basic console output and input polling using the > > Goldfish MMIO interface. > > > > Signed-off-by: Kuan-Wei Chiu <[email protected]> > > --- > > Changes in v3: > > - Remove unnecessary type casts for MMIO register access. > > > > MAINTAINERS | 6 ++ > > drivers/serial/Kconfig | 8 +++ > > drivers/serial/Makefile | 1 + > > drivers/serial/serial_goldfish.c | 102 +++++++++++++++++++++++++++++++ > > include/goldfish_tty.h | 18 ++++++ > > 5 files changed, 135 insertions(+) > > create mode 100644 drivers/serial/serial_goldfish.c > > create mode 100644 include/goldfish_tty.h > > > > diff --git a/MAINTAINERS b/MAINTAINERS > > index 6ce0bbce13d..da4a6e4d518 100644 > > --- a/MAINTAINERS > > +++ b/MAINTAINERS > > @@ -1259,6 +1259,12 @@ S: Maintained > > F: drivers/misc/gsc.c > > F: include/gsc.h > > +GOLDFISH SERIAL DRIVER > > +M: Kuan-Wei Chiu <[email protected]> > > +S: Maintained > > +F: drivers/serial/serial_goldfish.c > > +F: include/goldfish_tty.h > > + > > I2C > > M: Heiko Schocher <[email protected]> > > S: Maintained > > diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig > > index 371d7aa5bba..b84cb9ec781 100644 > > --- a/drivers/serial/Kconfig > > +++ b/drivers/serial/Kconfig > > @@ -1193,4 +1193,12 @@ config SYS_SDMR > > depends on MPC8XX_CONS > > default 0x0 > > +config SERIAL_GOLDFISH > > + bool "Goldfish TTY support" > > + depends on DM_SERIAL > > + help > > + Select this to enable support for the Goldfish TTY serial port. > > + This virtual device is commonly used by QEMU virtual machines > > + (e.g. m68k virt) for console output. > > + > > endif > > diff --git a/drivers/serial/Makefile b/drivers/serial/Makefile > > index 8eaae62b0fc..fe8d23be512 100644 > > --- a/drivers/serial/Makefile > > +++ b/drivers/serial/Makefile > > @@ -63,3 +63,4 @@ obj-$(CONFIG_XTENSA_SEMIHOSTING_SERIAL) += > > serial_xtensa_semihosting.o > > obj-$(CONFIG_S5P4418_PL011_SERIAL) += serial_s5p4418_pl011.o > > obj-$(CONFIG_UART4_SERIAL) += serial_adi_uart4.o > > +obj-$(CONFIG_SERIAL_GOLDFISH) += serial_goldfish.o > > diff --git a/drivers/serial/serial_goldfish.c > > b/drivers/serial/serial_goldfish.c > > new file mode 100644 > > index 00000000000..1d2977d809d > > --- /dev/null > > +++ b/drivers/serial/serial_goldfish.c > > @@ -0,0 +1,102 @@ > > +// SPDX-License-Identifier: GPL-2.0-or-later > > +/* > > + * Copyright (C) 2025, Kuan-Wei Chiu <[email protected]> > > + * Goldfish TTY driver for U-Boot > > + */ > > + > > +#include <asm/io.h> > > +#include <dm.h> > > +#include <goldfish_tty.h> > > +#include <linux/types.h> > > +#include <serial.h> > > + > > +/* Goldfish TTY Register Offsets */ > > +#define GOLDFISH_TTY_PUT_CHAR 0x00 > > +#define GOLDFISH_TTY_BYTES_READY 0x04 > > +#define GOLDFISH_TTY_CMD 0x08 > > +#define GOLDFISH_TTY_DATA_PTR 0x10 > > +#define GOLDFISH_TTY_DATA_LEN 0x14 > > +#define GOLDFISH_TTY_DATA_PTR_HIGH 0x18 > > +#define GOLDFISH_TTY_VERSION 0x20 > > + > > +/* Commands */ > > +#define CMD_WRITE_BUFFER 2 > > +#define CMD_READ_BUFFER 3 > > + > > +struct goldfish_tty_priv { > > + void __iomem *base; > > + u8 rx_buf; > > +}; > > + > > +static int goldfish_serial_getc(struct udevice *dev) > > +{ > > + struct goldfish_tty_priv *priv = dev_get_priv(dev); > > + unsigned long paddr; > > + u32 count; > > + > > + count = __raw_readl(priv->base + GOLDFISH_TTY_BYTES_READY); > > + if (count == 0) > > + return -EAGAIN; > > + > > + paddr = virt_to_phys((void *)&priv->rx_buf); > > + > > + __raw_writel(0, priv->base + GOLDFISH_TTY_DATA_PTR_HIGH); > > + __raw_writel(paddr, priv->base + GOLDFISH_TTY_DATA_PTR); > > + __raw_writel(1, priv->base + GOLDFISH_TTY_DATA_LEN); > > + __raw_writel(CMD_READ_BUFFER, priv->base + GOLDFISH_TTY_CMD); > > + > > + return priv->rx_buf; > > +} > > + > > +static int goldfish_serial_putc(struct udevice *dev, const char ch) > > +{ > > + struct goldfish_tty_priv *priv = dev_get_priv(dev); > > + > > + __raw_writel(ch, priv->base + GOLDFISH_TTY_PUT_CHAR); > > + > > + return 0; > > +} > > + > > +static int goldfish_serial_pending(struct udevice *dev, bool input) > > +{ > > + struct goldfish_tty_priv *priv = dev_get_priv(dev); > > + > > + if (input) > > + return __raw_readl(priv->base + GOLDFISH_TTY_BYTES_READY); > > + > > + return 0; > > +} > > + > > +static int goldfish_serial_probe(struct udevice *dev) > > +{ > > + struct goldfish_tty_priv *priv = dev_get_priv(dev); > > + struct goldfish_tty_plat *plat = dev_get_plat(dev); > > + > > + if (!plat) > > + return -EINVAL; > > + > > + priv->base = plat->base; > > The Linux binding documentation in > Documentation/devicetree/bindings/goldfish/tty.txt has this example: > > goldfish_tty@1f004000 { > compatible = "google,goldfish-tty"; > reg = <0x1f004000 0x1000>; > interrupts = <0xc>; > }; > > The driver should take the reg value as address and use plat->base only as > fallback for devices that don't provide a proper device-tree. > > We already do this for the RTC driver. Please, apply the same logic to all > Goldfish drivers.
Agreed. Will do this for both tty and timer drivers in the next version. Regards, Kuan-Wei
