Re: [U-Boot] [PATCH 5/6] serial: ns16550: fix debug uart putc called before init
On Tue, Oct 23, 2018 at 11:01 AM Marek Vasut wrote: > > On 10/19/2018 05:25 AM, Simon Glass wrote: > > On 9 August 2018 at 13:04, Simon Goldschmidt > > 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. > >> > >> Tested on socfpga_cyclone5_socrates. > >> > >> Signed-off-by: Simon Goldschmidt > >> --- > >> v2: > >> - this patch is new in v2 of the series. It replaces the printf/debug > >> change in reset_manager_gen5.c from v1 > >> > >> drivers/serial/ns16550.c | 18 -- > >> 1 file changed, 16 insertions(+), 2 deletions(-) > > > > We cannot use global_data before it is set up, so I think this is the > > best solution. > > > > Acked-by: Simon Glass > > So there's no GD available when using debug uart ? Hum. > > btw. Does the NS16550_read_baud_divisor() need to be called within the > while loop ? No. I just decided to put it there so that it is not executed unless we wait in a tight loop anyway. So if the transmit buffer is empty, code flow is unchanged by this patch. Only if it is not empty, the baud divisor is read. But in this case, we would cycle the while loop a few hundred times, anyway, I guess... Simon Applied to u-boot-dm/next, thanks! ___ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
Re: [U-Boot] [PATCH 5/6] serial: ns16550: fix debug uart putc called before init
On Tue, Oct 23, 2018 at 11:01 AM Marek Vasut wrote: > > On 10/19/2018 05:25 AM, Simon Glass wrote: > > On 9 August 2018 at 13:04, Simon Goldschmidt > > 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. > >> > >> Tested on socfpga_cyclone5_socrates. > >> > >> Signed-off-by: Simon Goldschmidt > >> --- > >> v2: > >> - this patch is new in v2 of the series. It replaces the printf/debug > >> change in reset_manager_gen5.c from v1 > >> > >> drivers/serial/ns16550.c | 18 -- > >> 1 file changed, 16 insertions(+), 2 deletions(-) > > > > We cannot use global_data before it is set up, so I think this is the > > best solution. > > > > Acked-by: Simon Glass > > So there's no GD available when using debug uart ? Hum. > > btw. Does the NS16550_read_baud_divisor() need to be called within the > while loop ? No. I just decided to put it there so that it is not executed unless we wait in a tight loop anyway. So if the transmit buffer is empty, code flow is unchanged by this patch. Only if it is not empty, the baud divisor is read. But in this case, we would cycle the while loop a few hundred times, anyway, I guess... Simon ___ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
Re: [U-Boot] [PATCH 5/6] serial: ns16550: fix debug uart putc called before init
On 10/19/2018 05:25 AM, Simon Glass wrote: > On 9 August 2018 at 13:04, Simon Goldschmidt > 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. >> >> Tested on socfpga_cyclone5_socrates. >> >> Signed-off-by: Simon Goldschmidt >> --- >> v2: >> - this patch is new in v2 of the series. It replaces the printf/debug >> change in reset_manager_gen5.c from v1 >> >> drivers/serial/ns16550.c | 18 -- >> 1 file changed, 16 insertions(+), 2 deletions(-) > > We cannot use global_data before it is set up, so I think this is the > best solution. > > Acked-by: Simon Glass So there's no GD available when using debug uart ? Hum. btw. Does the NS16550_read_baud_divisor() need to be called within the while loop ? -- Best regards, Marek Vasut ___ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
Re: [U-Boot] [PATCH 5/6] serial: ns16550: fix debug uart putc called before init
On 9 August 2018 at 13:04, Simon Goldschmidt 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. > > Tested on socfpga_cyclone5_socrates. > > Signed-off-by: Simon Goldschmidt > --- > v2: > - this patch is new in v2 of the series. It replaces the printf/debug > change in reset_manager_gen5.c from v1 > > drivers/serial/ns16550.c | 18 -- > 1 file changed, 16 insertions(+), 2 deletions(-) We cannot use global_data before it is set up, so I think this is the best solution. Acked-by: Simon Glass Regards, Simon ___ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
Re: [U-Boot] [PATCH 5/6] serial: ns16550: fix debug uart putc called before init
On 08/10/2018 01:37 PM, Simon Goldschmidt wrote:
> 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 wrote:
>> On 08/09/2018 11:13 PM, Adam Ford wrote:
>>> On Thu, Aug 9, 2018 at 2:08 PM Simon Goldschmidt
>>> 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(_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, much appreciated :)
--
Best regards,
Marek Vasut
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Re: [U-Boot] [PATCH 5/6] serial: ns16550: fix debug uart putc called before init
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 wrote:
On 08/09/2018 11:13 PM, Adam Ford wrote:
On Thu, Aug 9, 2018 at 2:08 PM Simon Goldschmidt
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(_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
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Re: [U-Boot] [PATCH 5/6] serial: ns16550: fix debug uart putc called before init
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 wrote:
On 08/09/2018 11:13 PM, Adam Ford wrote:
> On Thu, Aug 9, 2018 at 2:08 PM Simon Goldschmidt
> 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(_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.
--
Best regards,
Marek Vasut
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Re: [U-Boot] [PATCH 5/6] serial: ns16550: fix debug uart putc called before init
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 wrote:
On 08/09/2018 11:13 PM, Adam Ford wrote:
On Thu, Aug 9, 2018 at 2:08 PM Simon Goldschmidt
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(_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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Re: [U-Boot] [PATCH 5/6] serial: ns16550: fix debug uart putc called before init
On 08/10/2018 12:35 AM, Andy Shevchenko wrote:
> On Fri, Aug 10, 2018 at 12:45 AM, Marek Vasut wrote:
>> On 08/09/2018 11:13 PM, Adam Ford wrote:
>>> On Thu, Aug 9, 2018 at 2:08 PM Simon Goldschmidt
>>> 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(_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 ? The real problem I believe
is that someone can call debug UART print/read functions before it is
inited.
--
Best regards,
Marek Vasut
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Re: [U-Boot] [PATCH 5/6] serial: ns16550: fix debug uart putc called before init
On Fri, Aug 10, 2018 at 12:45 AM, Marek Vasut wrote:
> On 08/09/2018 11:13 PM, Adam Ford wrote:
>> On Thu, Aug 9, 2018 at 2:08 PM Simon Goldschmidt
>> 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(_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?
--
With Best Regards,
Andy Shevchenko
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Re: [U-Boot] [PATCH 5/6] serial: ns16550: fix debug uart putc called before init
On 08/09/2018 11:13 PM, Adam Ford wrote:
> On Thu, Aug 9, 2018 at 2:08 PM Simon Goldschmidt
> 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.
>>
>> Tested on socfpga_cyclone5_socrates.
>>
>> Signed-off-by: Simon Goldschmidt
>> ---
>> v2:
>> - this patch is new in v2 of the series. It replaces the printf/debug
>> change in reset_manager_gen5.c from v1
>>
>> drivers/serial/ns16550.c | 18 --
>> 1 file changed, 16 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c
>> index 9c80090aa7..475075c03c 100644
>> --- a/drivers/serial/ns16550.c
>> +++ b/drivers/serial/ns16550.c
>> @@ -266,12 +266,26 @@ static inline void _debug_uart_init(void)
>> serial_dout(_port->lcr, UART_LCRVAL);
>> }
>>
>> +static inline int NS16550_read_baud_divisor(struct NS16550 *com_port)
>> +{
>> + int ret;
>> +
>> + serial_dout(_port->lcr, UART_LCR_BKSE | UART_LCRVAL);
>> + ret = serial_din(_port->dll) & 0xff;
>> + ret |= (serial_din(_port->dlm) & 0xff) << 8;
>> + serial_dout(_port->lcr, UART_LCRVAL);
>> +
>> + return ret;
>> +}
>> +
>> static inline void _debug_uart_putc(int ch)
>> {
>> struct NS16550 *com_port = (struct NS16550 *)CONFIG_DEBUG_UART_BASE;
>>
>> - while (!(serial_din(_port->lsr) & UART_LSR_THRE))
>> - ;
>> + while (!(serial_din(_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 ?
--
Best regards,
Marek Vasut
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Re: [U-Boot] [PATCH 5/6] serial: ns16550: fix debug uart putc called before init
On Thu, Aug 9, 2018 at 2:08 PM Simon Goldschmidt
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.
>
> Tested on socfpga_cyclone5_socrates.
>
> Signed-off-by: Simon Goldschmidt
> ---
> v2:
> - this patch is new in v2 of the series. It replaces the printf/debug
> change in reset_manager_gen5.c from v1
>
> drivers/serial/ns16550.c | 18 --
> 1 file changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c
> index 9c80090aa7..475075c03c 100644
> --- a/drivers/serial/ns16550.c
> +++ b/drivers/serial/ns16550.c
> @@ -266,12 +266,26 @@ static inline void _debug_uart_init(void)
> serial_dout(_port->lcr, UART_LCRVAL);
> }
>
> +static inline int NS16550_read_baud_divisor(struct NS16550 *com_port)
> +{
> + int ret;
> +
> + serial_dout(_port->lcr, UART_LCR_BKSE | UART_LCRVAL);
> + ret = serial_din(_port->dll) & 0xff;
> + ret |= (serial_din(_port->dlm) & 0xff) << 8;
> + serial_dout(_port->lcr, UART_LCRVAL);
> +
> + return ret;
> +}
> +
> static inline void _debug_uart_putc(int ch)
> {
> struct NS16550 *com_port = (struct NS16550 *)CONFIG_DEBUG_UART_BASE;
>
> - while (!(serial_din(_port->lsr) & UART_LSR_THRE))
> - ;
> + while (!(serial_din(_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.
just my two-cents.
adam
> + return;
> + }
> serial_dout(_port->thr, ch);
> }
>
> --
> 2.17.1
>
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