mirror of
https://github.com/AsahiLinux/u-boot
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725cf89512
At the moment, the U-Boot serial_msm driver does not initialize the
UART_DM_DMEN register with the required value. Usually this does not
cause any problems, because there is Qualcomm's LK bootloader running
before U-Boot which initializes the register with the correct value.
It's important that this register is initialized correctly, because
the U-Boot driver does not make use of the BAM/DMA or single character
mode functionality of the UART controller. A different bootloader
before U-Boot might initialize the register differently.
For example, on DragonBoard 410c U-Boot can also be installed to the
"aboot" partition (replacing LK entirely). In this case U-Boot is
loaded directly by SBL, which seems to use the single-character mode
for some reason. In single character mode there is always just one
char in the FIFO, instead of the 4 characters expected by
msm_serial_fetch(). It also causes issues with "earlycon" later in
the Linux kernel, which tries to output 4 chars at once,
but only the first char will be written.
This causes early UART log in Linux to be corrupted like this:
[ 00ano:ameoi .Q1B[ 00ac _idaM00080oo'ahani-lcle._20). 15NdNii 5 SPMSJ20:U2
[ 00rkoolmsamel
[ 00Fw ]elamletopsioble
[ 00ore
instead of
[ 0.000000] Booting Linux on physical CPU 0x0000000000 [0x410fd030]
[ 0.000000] Machine model: Qualcomm Technologies, Inc. APQ 8016 SBC
[ 0.000000] earlycon: msm_serial_dm0 at MMIO 0x00000000078b0000 (options '')
[ 0.000000] printk: bootconsole [msm_serial_dm0] enabled
Make sure to initialize UART_DM_DMEN correctly to fix this issue
when loading U-Boot directly after SBL (instead of through LK).
There is no functional difference when loading U-Boot through LK
since LK also initializes UART_DM_DMEN to 0x0. [1]
[1]: https://git.linaro.org/landing-teams/working/qualcomm/lk.git/tree/platform/msm_shared/uart_dm.c?h=dragonboard410c-LA.BR.1.2.7-03810-8x16.0-linaro3#n203
Cc: Ramon Fried <rfried.dev@gmail.com>
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>
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|---|---|---|
| .. | ||
| altera_jtag_uart.c | ||
| altera_uart.c | ||
| arm_dcc.c | ||
| atmel_usart.c | ||
| atmel_usart.h | ||
| Kconfig | ||
| lpc32xx_hsuart.c | ||
| Makefile | ||
| ns16550.c | ||
| sandbox.c | ||
| serial-uclass.c | ||
| serial.c | ||
| serial_ar933x.c | ||
| serial_arc.c | ||
| serial_bcm283x_mu.c | ||
| serial_bcm283x_pl011.c | ||
| serial_bcm6345.c | ||
| serial_coreboot.c | ||
| serial_cortina.c | ||
| serial_efi.c | ||
| serial_intel_mid.c | ||
| serial_linflexuart.c | ||
| serial_lpuart.c | ||
| serial_mcf.c | ||
| serial_meson.c | ||
| serial_mpc8xx.c | ||
| serial_msm.c | ||
| serial_mt7620.c | ||
| serial_mtk.c | ||
| serial_mvebu_a3700.c | ||
| serial_mxc.c | ||
| serial_ns16550.c | ||
| serial_nulldev.c | ||
| serial_octeon_bootcmd.c | ||
| serial_octeon_pcie_console.c | ||
| serial_omap.c | ||
| serial_owl.c | ||
| serial_pic32.c | ||
| serial_pl01x.c | ||
| serial_pl01x_internal.h | ||
| serial_pxa.c | ||
| serial_rockchip.c | ||
| serial_s5p.c | ||
| serial_sh.c | ||
| serial_sh.h | ||
| serial_sifive.c | ||
| serial_sti_asc.c | ||
| serial_stm32.c | ||
| serial_stm32.h | ||
| serial_uniphier.c | ||
| serial_xen.c | ||
| serial_xuartlite.c | ||
| serial_zynq.c | ||
| usbtty.c | ||
| usbtty.h | ||