[PATCH 3/3] ARM: early_printk: use printascii() rather than printch()

[Robin Murphy]

On 31/10/17 16:22, Nicolas Pitre wrote:
> On Tue, 31 Oct 2017, Chris Brandt wrote:
> 
>> On Sunday, October 01, 2017 1, Nicolas Pitre wrote:
>>> With printch() the console messages are sent out one character at a time
>>> which is agonizingly slow especially with semihosting as the whole trap
>>> intercept, remote byte access, and system resume danse is performed for
>>> every single character across a relatively slow remote debug connection.
>>> Let's use printascii() to send a whole string at once. This is also going
>>> to be more efficient, albeit to a quite lesser extent, with serial ports
>>> as well.
>>>
>>> Signed-off-by: Nicolas Pitre <nico at linaro.org>
>>> ---
>>>  arch/arm/kernel/early_printk.c | 16 ++++++++++------
>>>  1 file changed, 10 insertions(+), 6 deletions(-)
>>
>> Now that this patch has hit -next, I'm noticing an issue with it.
>>
>> There are no carriage returns, just line feeds, which makes for a very 
>> ugly display.
> 
> Hmmm....
> 
> If you look at printascii in arch/arm/kernel/debug.S you'll find the 
> following code:
> 
> 1:              waituart r2, r3
>                 senduart r1, r3
>                 busyuart r2, r3
>                 teq     r1, #'\n'
>                 moveq   r1, #'\r'
>                 beq     1b
> 
> Why is that not working for you?

By inspection, the removed early_write() code inserted the '\r' before
the '\n' in the usual fashion; the printascii() code above ends up doing
the reverse, and I can imagine the atypical "\n\r" sequence probably
confuses some terminals trying to be clever with line ending detection.

Robin.

> 
> Are you using semihosting?
> 
> Do you have another printascii implementation?
> 
> 
> Nicolas
> 
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