linux-kernel - Re: [PATCH 2/4] serial: 8250: of: Load TX FIFO Load Size from DT

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Date:   Fri, 16 Sep 2016 15:52:55 -0500
From:   Thor Thayer <tthayer@...nsource.altera.com>
To:     Rob Herring <robh@...nel.org>
CC:     <gregkh@...uxfoundation.org>, <mark.rutland@....com>,
        <lftan@...era.com>, <jslaby@...e.com>, <arnd@...db.de>,
        <peter@...leysoftware.com>, <andriy.shevchenko@...ux.intel.com>,
        <anton.wuerfel@....de>, <phillip.raffeck@....de>,
        <yegorslists@...glemail.com>, <matwey@....msu.ru>,
        <mail@...iej.szmigiero.name>, <peter.ujfalusi@...com>,
        <jonathanh@...dia.com>, <dongsheng.wang@....com>,
        <luis@...ethencourt.com>, <linux-kernel@...r.kernel.org>,
        <linux-serial@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <tthayer.linux@...il.com>, <nios2-dev@...ts.rocketboards.org>
Subject: Re: [PATCH 2/4] serial: 8250: of: Load TX FIFO Load Size from DT

Hi Rob,

On 09/16/2016 02:20 PM, Rob Herring wrote:
> On Thu, Sep 08, 2016 at 11:12:19AM -0500, tthayer@...nsource.altera.com wrote:
>> From: Thor Thayer <tthayer@...nsource.altera.com>
>>
>> Initialize the tx_loadsz parameter if it is defined in the
>> device tree.
>>
>> Signed-off-by: Thor Thayer <tthayer@...nsource.altera.com>
>> ---
>>  drivers/tty/serial/8250/8250_of.c |    6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/drivers/tty/serial/8250/8250_of.c b/drivers/tty/serial/8250/8250_of.c
>> index 38963d7..3e4be2f 100644
>> --- a/drivers/tty/serial/8250/8250_of.c
>> +++ b/drivers/tty/serial/8250/8250_of.c
>> @@ -195,6 +195,7 @@ static int of_platform_serial_probe(struct platform_device *ofdev)
>>  	switch (port_type) {
>>  	case PORT_8250 ... PORT_MAX_8250:
>>  	{
>> +		u32 prop;
>>  		struct uart_8250_port port8250;
>>  		memset(&port8250, 0, sizeof(port8250));
>>  		port8250.port = port;
>> @@ -202,6 +203,11 @@ static int of_platform_serial_probe(struct platform_device *ofdev)
>>  		if (port.fifosize)
>>  			port8250.capabilities = UART_CAP_FIFO;
>>
>> +		/* Check for TX fifo load size */
>> +		if (of_property_read_u32(ofdev->dev.of_node,
>> +					 "tx-loadsz", &prop) == 0)
>> +			port8250.tx_loadsz = prop;
>
> This can be simplified to:
>
> of_property_read_u32(ofdev->dev.of_node, "tx-loadsz", &port8250.tx_loadsz);
>
>
Yes, I originally had it implemented using that function but then I 
realized the port8250.tx_loadsz is an unsigned int and therefore can 
change size on different platforms.

The assignment handles that. In retrospect, I should probably change 
this to a of_property_read_u8() anyway so that it won't cause compile 
warnings in the smaller architectures.

Thank you for reviewing and the comments.

Thor

>> +
>>  		if (of_property_read_bool(ofdev->dev.of_node,
>>  					  "auto-flow-control"))
>>  			port8250.capabilities |= UART_CAP_AFE;
>> --
>> 1.7.9.5
>>