On 10.08.2018 00:41, Marek Vasut wrote:
On 08/10/2018 12:35 AM, Andy Shevchenko wrote:
On Fri, Aug 10, 2018 at 12:45 AM, Marek Vasut <ma...@denx.de> wrote:
On 08/09/2018 11:13 PM, Adam Ford wrote:
On Thu, Aug 9, 2018 at 2:08 PM Simon Goldschmidt
<simon.k.r.goldschm...@gmail.com> wrote:
If _debug_uart_putc() is called before _debug_uart_init(), the
ns16550 debug uart driver hangs in a tight loop waiting for the
tx FIFO to get empty.
As this can happen via a printf sneaking in before the port calls
debug_uart_init(), let's rather ignore characters before the debug
uart is initialized.
This is done by reading the baudrate divisor and aborting if is zero.
static inline void _debug_uart_putc(int ch)
{
struct NS16550 *com_port = (struct NS16550 *)CONFIG_DEBUG_UART_BASE;
+ while (!(serial_din(&com_port->lsr) & UART_LSR_THRE)) {
+ if (!NS16550_read_baud_divisor(com_port))
Unless there is a change that the read_baud_divisor will change while
we're waiting for the character, could we move this check before the
while statement? This would reduce the check for the divisor to 1x
and the while statement would only have one comparison to do. I
realize it's rather trivial, but the way I see it, there is no reason
to do the while statement at all if the read_baud_divisor fails and
there if there is a baud divisor, we should only need to check it
once.
This looks like a massive hack -- what about having a flag which says
that the debug uart was/was not inited somewhere ?
Agree, why not to cache divisor value, for example, instead of doing slow I/O?
But why do we care about the divisor at all ?
Because if the divisor is zero, the UART is disabled.
The real problem I believe
is that someone can call debug UART print/read functions before it is
inited.
I know this is a hack. I did it like that because I need something like
this to get debug uart to work on socfpga gen5 (there always is a printf
before debug uart init is possible).
A generic solution for all debug uarts would be better of course, but
given the point in SPL runtime, we might have to add a field to 'gd' for
that, or does a global variable work at that point already?
Simon
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