On 10.08.2018 11:51, Marek Vasut wrote:
On 08/10/2018 07:22 AM, Simon Goldschmidt wrote:
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 marex@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.goldschmidt@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?
GD field might be needed indeed.
Right. I'll drop this patch in the next version of the series and instead I'll try to work out something that works for all debug uarts drivers using a gd field.
Thanks,
Simon