[1/4] Documentation: dt: serial: Add TX FIFO load size
diff mbox

Message ID 1473351141-9239-2-git-send-email-tthayer@opensource.altera.com
State Changes Requested, archived
Headers show

Commit Message

tthayer@opensource.altera.com Sept. 8, 2016, 4:12 p.m. UTC
From: Thor Thayer <tthayer@opensource.altera.com>

Add the device tree bindings needed to support the TX FIFO
load size.

Signed-off-by: Thor Thayer <tthayer@opensource.altera.com>
---
 Documentation/devicetree/bindings/serial/8250.txt |    1 +
 1 file changed, 1 insertion(+)

Comments

Rob Herring Sept. 16, 2016, 7:19 p.m. UTC | #1
On Thu, Sep 08, 2016 at 11:12:18AM -0500, tthayer@opensource.altera.com wrote:
> From: Thor Thayer <tthayer@opensource.altera.com>
> 
> Add the device tree bindings needed to support the TX FIFO
> load size.
> 
> Signed-off-by: Thor Thayer <tthayer@opensource.altera.com>
> ---
>  Documentation/devicetree/bindings/serial/8250.txt |    1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/Documentation/devicetree/bindings/serial/8250.txt b/Documentation/devicetree/bindings/serial/8250.txt
> index f5561ac..93de5ef 100644
> --- a/Documentation/devicetree/bindings/serial/8250.txt
> +++ b/Documentation/devicetree/bindings/serial/8250.txt
> @@ -45,6 +45,7 @@ Optional properties:
>  - {rts,cts,dtr,dsr,rng,dcd}-gpios: specify a GPIO for RTS/CTS/DTR/DSR/RI/DCD
>    line respectively. It will use specified GPIO instead of the peripheral
>    function pin for the UART feature. If unsure, don't specify this property.
> +- tx-loadsz: the number of bytes that can be loaded into the TX FIFO.

It seems you don't really need to know the loadsz, but just need the 
threshold trigger level. So just use that directly. And please check if 
any other UARTs have threshold properties. i.MX has programmable 
thresholds.

Rob
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tthayer@opensource.altera.com Sept. 16, 2016, 8:47 p.m. UTC | #2
Hi Rob,

On 09/16/2016 02:19 PM, Rob Herring wrote:
> On Thu, Sep 08, 2016 at 11:12:18AM -0500, tthayer@opensource.altera.com wrote:
>> From: Thor Thayer <tthayer@opensource.altera.com>
>>
>> Add the device tree bindings needed to support the TX FIFO
>> load size.
>>
>> Signed-off-by: Thor Thayer <tthayer@opensource.altera.com>
>> ---
>>  Documentation/devicetree/bindings/serial/8250.txt |    1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/Documentation/devicetree/bindings/serial/8250.txt b/Documentation/devicetree/bindings/serial/8250.txt
>> index f5561ac..93de5ef 100644
>> --- a/Documentation/devicetree/bindings/serial/8250.txt
>> +++ b/Documentation/devicetree/bindings/serial/8250.txt
>> @@ -45,6 +45,7 @@ Optional properties:
>>  - {rts,cts,dtr,dsr,rng,dcd}-gpios: specify a GPIO for RTS/CTS/DTR/DSR/RI/DCD
>>    line respectively. It will use specified GPIO instead of the peripheral
>>    function pin for the UART feature. If unsure, don't specify this property.
>> +- tx-loadsz: the number of bytes that can be loaded into the TX FIFO.
>
> It seems you don't really need to know the loadsz, but just need the
> threshold trigger level. So just use that directly. And please check if
> any other UARTs have threshold properties. i.MX has programmable
> thresholds.
>
> Rob
>

Yes, it is correct that I only really need the loadsz, but there is a 
tx-loadsz parameter in the uart_8250_port structure. Since there 
currently isn't a way to update the default value of tx-loadsz from 
device tree, I thought this would be useful for other 8250 UARTs as well.

Yes, there are a couple of 8250 compatible UARTs that have programmable 
thresholds. The SC16654 and SC16C650 are 2 examples. However, I didn't 
see the programmable TX threshold implemented.

I looked at the i.MX UARTs but I don't see a programmable threshold 
parameter in the bindings( 
Documentation/devicetree/bindings/serial/fsl-imx-uart.txt).

I'm assuming you're saying that I should use the same binding names for 
this transmit threshold if they are available?

Thank you for reviewing and for the comments.

Thor


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Patch
diff mbox

diff --git a/Documentation/devicetree/bindings/serial/8250.txt b/Documentation/devicetree/bindings/serial/8250.txt
index f5561ac..93de5ef 100644
--- a/Documentation/devicetree/bindings/serial/8250.txt
+++ b/Documentation/devicetree/bindings/serial/8250.txt
@@ -45,6 +45,7 @@  Optional properties:
 - {rts,cts,dtr,dsr,rng,dcd}-gpios: specify a GPIO for RTS/CTS/DTR/DSR/RI/DCD
   line respectively. It will use specified GPIO instead of the peripheral
   function pin for the UART feature. If unsure, don't specify this property.
+- tx-loadsz: the number of bytes that can be loaded into the TX FIFO.
 
 Note:
 * fsl,ns16550: