Hi Sathya,
The seL4 kernel defines available kernel devices in the platform dependent
hardware.h file.
The kernel_devices[] structure contains all the hardware devices that the
kernel needs access to. For most platforms, this is just the GIC, but if
CONFIG_PRINTING is enabled, the uart is added as well.
The code below is from the zynqmp hardware.h file:
#ifdef CONFIG_PRINTING
},
{
/* UART */
UART_PADDR,
UART_PPTR,
true /* armExecuteNever */
#endif /* CONFIG_PRINTING */
}
So that device defines the UART physical address, virtual address, and whether
the device is allowed to execute. The kernel_devices structure gets used with
the map_kernel_devices function so that the UART gets mapped from UART_PADDR ->
UART_PPTR. Software can then use the virtual address to send and receive
characters from the UART.
#define UART_REG(x) ((volatile uint32_t *)(UART_PPTR + (x)))
while (!(*UART_REG(XUARTPS_SR) & XUARTPS_SR_TXEMPTY));
*UART_REG(XUARTPS_FIFO) = c;
Let me know if you have any other questions.
Chris Guikema
Embedded Systems Engineer
DornerWorks, Ltd.
From: Devel [mailto:[email protected]] On Behalf Of Sathya Narayanan N
Sent: Thursday, July 19, 2018 4:27 AM
To: [email protected]
Subject: Re: [seL4] Understanding how SEL4 recognises UART on board
Hi Experts,
I am curious to know how SEL4 recognises the existence of UART on the board and
mapped to a particular memory address.
I see there is no DTB/ DTS files read from memory.
could someone help me understand the concept here ?
Or is it something hardcoded in the kernel ?
--
regards,
Sathya
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