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serial: bcm283x_mu: Detect disabled serial device

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On the raspberry pi, you can disable the serial port to gain dynamic frequency
scaling which can get handy at times.

However, in such a configuration the serial controller gets its rx queue filled
up with zero bytes which then happily get transmitted on to whoever calls
getc() today.

This patch adds detection logic for that case by checking whether the RX pin is
mapped to GPIO15 and disables the mini uart if it is not mapped properly.

That way we can leave the driver enabled in the tree and can determine during
runtime whether serial is usable or not, having a single binary that allows for
uart and non-uart operation.

Signed-off-by: Alexander Graf <agraf@suse.de>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
This commit is contained in:
Alexander Graf 2016-08-15 17:48:51 +02:00 committed by Tom Rini
parent 04a993fe11
commit 601147b06a
7 changed files with 43 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

34
board/raspberrypi/rpi/rpi.c
View File

@ -50,7 +50,7 @@ U_BOOT_DEVICE(bcm2835_serials) = {
.platdata = &serial_platdata,
};
#else
static const struct bcm283x_mu_serial_platdata serial_platdata = {
static struct bcm283x_mu_serial_platdata serial_platdata = {
.base = 0x3f215040,
.clock = 250000000,
.skip_init = true,
@ -452,6 +452,38 @@ int board_init(void)
return power_on_module(BCM2835_MBOX_POWER_DEVID_USB_HCD);
}
#ifndef CONFIG_PL01X_SERIAL
static bool rpi_is_serial_active(void)
{
int serial_gpio = 15;
struct udevice *dev;
/*
* The RPi3 disables the mini uart by default. The easiest way to find
* out whether it is available is to check if the RX pin is muxed.
*/
if (uclass_first_device(UCLASS_GPIO, &dev) || !dev)
return true;
if (bcm2835_gpio_get_func_id(dev, serial_gpio) != BCM2835_GPIO_ALT5)
return false;
return true;
}
#endif
int board_early_init_f(void)
{
#ifndef CONFIG_PL01X_SERIAL
/* Disable mini-UART I/O if it's not pinmuxed to our pins */
if (!rpi_is_serial_active())
serial_platdata.disabled = true;
#endif
return 0;
}
int board_mmc_init(bd_t *bis)
{
ALLOC_CACHE_ALIGN_BUFFER(struct msg_get_clock_rate, msg_clk, 1);

2
configs/rpi_3_32b_defconfig
View File

@ -20,3 +20,5 @@ CONFIG_CMD_FAT=y
CONFIG_CMD_FS_GENERIC=y
CONFIG_PHYS_TO_BUS=y
CONFIG_OF_LIBFDT=y
# CONFIG_REQUIRE_SERIAL_CONSOLE is not set
CONFIG_SYS_MALLOC_F_LEN=0x2000

2
configs/rpi_3_defconfig
View File

@ -19,3 +19,5 @@ CONFIG_CMD_FAT=y
CONFIG_CMD_FS_GENERIC=y
CONFIG_PHYS_TO_BUS=y
CONFIG_OF_LIBFDT=y
# CONFIG_REQUIRE_SERIAL_CONSOLE is not set
CONFIG_SYS_MALLOC_F_LEN=0x2000

1
drivers/gpio/bcm2835_gpio.c
View File

@ -123,5 +123,6 @@ U_BOOT_DRIVER(gpio_bcm2835) = {
.id = UCLASS_GPIO,
.ops = &gpio_bcm2835_ops,
.probe = bcm2835_gpio_probe,
.flags = DM_FLAG_PRE_RELOC,
.priv_auto_alloc_size = sizeof(struct bcm2835_gpios),
};

3
drivers/serial/serial_bcm283x_mu.c
View File

@ -73,6 +73,9 @@ static int bcm283x_mu_serial_probe(struct udevice *dev)
struct bcm283x_mu_serial_platdata *plat = dev_get_platdata(dev);
struct bcm283x_mu_priv *priv = dev_get_priv(dev);
if (plat->disabled)
return -ENODEV;
priv->regs = (struct bcm283x_mu_regs *)plat->base;
return 0;

1
include/configs/rpi.h
View File

@ -16,6 +16,7 @@
/* Architecture, CPU, etc.*/
#define CONFIG_ARCH_CPU_INIT
#define CONFIG_BOARD_EARLY_INIT_F
/* Use SoC timer for AArch32, but architected timer for AArch64 */
#ifndef CONFIG_ARM64

1
include/dm/platform_data/serial_bcm283x_mu.h
View File

@ -19,6 +19,7 @@ struct bcm283x_mu_serial_platdata {
unsigned long base;
unsigned int clock;
bool skip_init;
bool disabled;
};
#endif