Re: [PATCH v3 0/6] hw/arm: xilinx_zynq: Fix upstream U-Boot boot failure

[Edgar E. Iglesias]

On Wed, Sep 01, 2021 at 08:45:15PM +0800, Bin Meng wrote:
> As of today, when booting upstream U-Boot for Xilinx Zynq, the UART
> does not receive anything. Debugging shows that the UART input clock
> frequency is zero which prevents the UART from receiving anything as.
> per the logic in uart_receive().
> 
> Note the U-Boot can still output data to the UART tx fifo, which should
> not happen, as the design seems to prevent the data transmission when
> clock is not enabled but somehow it only applies to the Rx side.
> 
> For anyone who is interested to give a try, here is the U-Boot defconfig:
> $ make xilinx_zynq_virt_defconfig
> 
> and QEMU commands to test U-Boot:
> $ qemu-system-arm -M xilinx-zynq-a9 -m 1G -display none -serial null -serial 
> stdio \
>     -device loader,file=u-boot-dtb.bin,addr=0x4000000,cpu-num=0
> 
> Note U-Boot used to boot properly in QEMU 4.2.0 which is the QEMU
> version used in current U-Boot's CI testing. The UART clock changes
> were introduced by the following 3 commits:
> 
> 38867cb7ec90 ("hw/misc/zynq_slcr: add clock generation for uarts")
> b636db306e06 ("hw/char/cadence_uart: add clock support")
> 5b49a34c6800 ("hw/arm/xilinx_zynq: connect uart clocks to slcr")

Thanks Bin,

On the entire series:

Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>