| Message ID | 6f94e7b0f1cfe98a640d7f9ff59f18f299fd0d7d.1564371527.git.stewart.hildebrand@dornerworks.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Raspberry Pi 4 support | expand |
On Mon, 29 Jul 2019 09:19:19 -0400 Stewart Hildebrand <stewart.hildebrand@dornerworks.com> wrote: Hi, > Per the BCM2835 peripherals datasheet [1] page 10: > "The UART core is build to emulate 16550 behaviour ... The implemented > UART is not a 16650 compatible UART However as far as possible the > first 8 control and status registers are laid out like a 16550 UART. Al > 16550 register bits which are not supported can be written but will be > ignored and read back as 0. All control bits for simple UART receive/ > transmit operations are available." > > Additionally, Linux uses the 8250/16550 driver for the aux UART [2]. > > Unfortunately the brcm,bcm2835-aux-uart device tree binding doesn't > have the reg-shift and reg-io-width properties [3]. Thus, the reg-shift > and reg-io-width properties are inherent properties of this UART. > > Thanks to Andre Przywara for contributing the reg-shift and > reg-io-width setting snippet. > > In my testing, I have relied on enable_uart=1 being set in config.txt, > a configuration file read by the Raspberry Pi's firmware. With > enable_uart=1, the firmware performs UART initialization. > > [1] https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2835/BCM2835-ARM-Peripherals.pdf > [2] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/drivers/tty/serial/8250/8250_bcm2835aux.c > [3] https://www.kernel.org/doc/Documentation/devicetree/bindings/serial/brcm,bcm2835-aux-uart.txt > > Signed-off-by: Stewart Hildebrand <stewart.hildebrand@dornerworks.com> Reviewed-by: Andre Przywara <andre.przywara@arm.com> Tested-by: Andre Przywara <andre.przywara@arm.com> Cheers, Andre. > --- > xen/drivers/char/ns16550.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c > index e518f2d790..8667de6d67 100644 > --- a/xen/drivers/char/ns16550.c > +++ b/xen/drivers/char/ns16550.c > @@ -1585,6 +1585,12 @@ static int __init ns16550_uart_dt_init(struct dt_device_node *dev, > if ( uart->reg_width != 1 && uart->reg_width != 4 ) > return -EINVAL; > > + if ( dt_device_is_compatible(dev, "brcm,bcm2835-aux-uart") ) > + { > + uart->reg_width = 4; > + uart->reg_shift = 2; > + } > + > res = platform_get_irq(dev, 0); > if ( ! res ) > return -EINVAL; > @@ -1611,6 +1617,7 @@ static const struct dt_device_match ns16550_dt_match[] __initconst = > DT_MATCH_COMPATIBLE("ns16550"), > DT_MATCH_COMPATIBLE("ns16550a"), > DT_MATCH_COMPATIBLE("snps,dw-apb-uart"), > + DT_MATCH_COMPATIBLE("brcm,bcm2835-aux-uart"), > { /* sentinel */ }, > }; >
Hi, On 29/07/2019 17:06, Andre Przywara wrote: > On Mon, 29 Jul 2019 09:19:19 -0400 > Stewart Hildebrand <stewart.hildebrand@dornerworks.com> wrote: > > Hi, > >> Per the BCM2835 peripherals datasheet [1] page 10: >> "The UART core is build to emulate 16550 behaviour ... The implemented >> UART is not a 16650 compatible UART However as far as possible the >> first 8 control and status registers are laid out like a 16550 UART. Al >> 16550 register bits which are not supported can be written but will be >> ignored and read back as 0. All control bits for simple UART receive/ >> transmit operations are available." >> >> Additionally, Linux uses the 8250/16550 driver for the aux UART [2]. >> >> Unfortunately the brcm,bcm2835-aux-uart device tree binding doesn't >> have the reg-shift and reg-io-width properties [3]. Thus, the reg-shift >> and reg-io-width properties are inherent properties of this UART. >> >> Thanks to Andre Przywara for contributing the reg-shift and >> reg-io-width setting snippet. >> >> In my testing, I have relied on enable_uart=1 being set in config.txt, >> a configuration file read by the Raspberry Pi's firmware. With >> enable_uart=1, the firmware performs UART initialization. >> >> [1] https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2835/BCM2835-ARM-Peripherals.pdf >> [2] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/drivers/tty/serial/8250/8250_bcm2835aux.c >> [3] https://www.kernel.org/doc/Documentation/devicetree/bindings/serial/brcm,bcm2835-aux-uart.txt >> >> Signed-off-by: Stewart Hildebrand <stewart.hildebrand@dornerworks.com> > > Reviewed-by: Andre Przywara <andre.przywara@arm.com> > Tested-by: Andre Przywara <andre.przywara@arm.com> Acked-by: Julien Grall <julien.grall@arm.com> Cheers,
diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c index e518f2d790..8667de6d67 100644 --- a/xen/drivers/char/ns16550.c +++ b/xen/drivers/char/ns16550.c @@ -1585,6 +1585,12 @@ static int __init ns16550_uart_dt_init(struct dt_device_node *dev, if ( uart->reg_width != 1 && uart->reg_width != 4 ) return -EINVAL; + if ( dt_device_is_compatible(dev, "brcm,bcm2835-aux-uart") ) + { + uart->reg_width = 4; + uart->reg_shift = 2; + } + res = platform_get_irq(dev, 0); if ( ! res ) return -EINVAL; @@ -1611,6 +1617,7 @@ static const struct dt_device_match ns16550_dt_match[] __initconst = DT_MATCH_COMPATIBLE("ns16550"), DT_MATCH_COMPATIBLE("ns16550a"), DT_MATCH_COMPATIBLE("snps,dw-apb-uart"), + DT_MATCH_COMPATIBLE("brcm,bcm2835-aux-uart"), { /* sentinel */ }, };
Per the BCM2835 peripherals datasheet [1] page 10: "The UART core is build to emulate 16550 behaviour ... The implemented UART is not a 16650 compatible UART However as far as possible the first 8 control and status registers are laid out like a 16550 UART. Al 16550 register bits which are not supported can be written but will be ignored and read back as 0. All control bits for simple UART receive/ transmit operations are available." Additionally, Linux uses the 8250/16550 driver for the aux UART [2]. Unfortunately the brcm,bcm2835-aux-uart device tree binding doesn't have the reg-shift and reg-io-width properties [3]. Thus, the reg-shift and reg-io-width properties are inherent properties of this UART. Thanks to Andre Przywara for contributing the reg-shift and reg-io-width setting snippet. In my testing, I have relied on enable_uart=1 being set in config.txt, a configuration file read by the Raspberry Pi's firmware. With enable_uart=1, the firmware performs UART initialization. [1] https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2835/BCM2835-ARM-Peripherals.pdf [2] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/drivers/tty/serial/8250/8250_bcm2835aux.c [3] https://www.kernel.org/doc/Documentation/devicetree/bindings/serial/brcm,bcm2835-aux-uart.txt Signed-off-by: Stewart Hildebrand <stewart.hildebrand@dornerworks.com> --- xen/drivers/char/ns16550.c | 7 +++++++ 1 file changed, 7 insertions(+)