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Date:	Mon, 01 Sep 2014 15:31:56 +0200
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
CC:	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	tony@...mide.com, balbi@...com, Vinod Koul <vinod.koul@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 05/15] tty: serial: Add 8250-core based omap driver

On 08/18/2014 03:46 PM, Heikki Krogerus wrote:
> On Fri, Aug 15, 2014 at 07:42:33PM +0200, Sebastian Andrzej Siewior wrote:
>> diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
>> index cc90c19..ab003b6 100644
>> --- a/drivers/tty/serial/8250/8250_core.c
>> +++ b/drivers/tty/serial/8250/8250_core.c
>> @@ -264,6 +264,12 @@ static const struct serial8250_config uart_config[] = {
>>  		.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
>>  		.flags		= UART_CAP_FIFO | UART_CAP_AFE,
>>  	},
>> +	[PORT_OMAP_16750] = {
>> +		.name		= "OMAP",
>> +		.fifo_size	= 64,
>> +		.tx_loadsz	= 64,
>> +		.flags		= UART_CAP_FIFO | UART_CAP_EFR | UART_CAP_SLEEP,
>> +	},
> 
> I don't think you need this. Reasons below...

For those it works. However I have to this value to something because
it can't stay PORT_UNKNOWN. So for now I took PORT_8250 because it is
not used anywhere in the code. The only side effect of this is that I
can't specify the name. I can live with this…

> 
>>  	[PORT_TEGRA] = {
>>  		.name		= "Tegra",
>>  		.fifo_size	= 32,
>> @@ -1390,6 +1396,8 @@ static void serial8250_stop_rx(struct uart_port *port)
>>  	serial8250_rpm_get(up);
>>  
>>  	up->ier &= ~UART_IER_RLSI;
>> +	if (port->type == PORT_OMAP_16750)
>> +		up->ier &= ~UART_IER_RDI;
> 
> I don't see any reason why this could not be always cleared regardless
> of the type:
> 
>         up->ier &= ~(UART_IER_RLSI | UART_IRE_RDI);
> 

I remember you brought that up recently asking Alan if it is okay doing
so. Since it looks sane to revert that bit on RX-stop, I will drop that
omap check here.

> [cut]
> 
> Since you are not calling serial8250_do_set_termios, 8250_core.c newer
> overrides the FCR set in this driver. However, if the FCR is a
> problem, since Yoshihiro added the member for it to struct
> uart_8250_port (commit aef9a7bd9), just make it possible for the probe
> drivers to provide also it's value:
> 
>  static int
> 
> So instead of using PORT_OMAP_16750:
>         up.port.type = PORT_16750;
>         up.capabilities = UART_CAP_FIFO | UART_CAP_EFR | UART_CAP_SLEEP;
> 
> and the fcr if needed.
>         up.fcr = ...
> 

That fcr value looks nice so I can't drop my private copy of it.  But
this FCR works different for RX trigger (the way it is used). Which
means to support user configurable RX-level I would need to overwrite
that callback. However since PORT_8250 does not supply any FCR values,
I can just ignore it for now.

>> +	up.port.iotype = UPIO_MEM32;
>> +	up.port.flags = UPF_BOOT_AUTOCONF | UPF_FIXED_PORT | UPF_FIXED_TYPE |
>> +		UPF_SOFT_FLOW | UPF_HARD_FLOW;
>> +	up.port.private_data = priv;
>> +
>> +	up.port.regshift = 2;
>> +	up.port.fifosize = 64;
> 
> You don't need to set the fifosize unless you want to replace the
> value you get from uart_config array.
Since you made me drop my uart_config array entry I keep this and add
the other values, too

>> +	up.port.set_termios = omap_8250_set_termios;
>> +	up.port.pm = omap_8250_pm;
>> +	up.port.startup = omap_8250_startup;
>> +	up.port.shutdown = omap_8250_shutdown;
>> +	up.port.throttle = omap_8250_throttle;
>> +	up.port.unthrottle = omap_8250_unthrottle;
>> +
>> +	if (pdev->dev.of_node) {
>> +		up.port.line = of_alias_get_id(pdev->dev.of_node, "serial");
>> +		of_property_read_u32(pdev->dev.of_node, "clock-frequency",
>> +				&up.port.uartclk);
>> +		priv->wakeirq = irq_of_parse_and_map(pdev->dev.of_node, 1);
>> +	} else {
>> +		up.port.line = pdev->id;
>> +	}
>> +
>> +	if (up.port.line < 0) {
>> +		dev_err(&pdev->dev, "failed to get alias/pdev id, errno %d\n",
>> +				up.port.line);
>> +		return -ENODEV;
>> +	}
>> +	if (!up.port.uartclk) {
>> +		up.port.uartclk = DEFAULT_CLK_SPEED;
>> +		dev_warn(&pdev->dev,
>> +				"No clock speed specified: using default: %d\n",
>> +				DEFAULT_CLK_SPEED);
>> +	}
>> +
>> +#ifdef CONFIG_PM_RUNTIME
>> +	up.capabilities |= UART_CAP_RPM;
>> +#endif
> 
> By setting this here, you will not get the capabilities from the
> uart_config[type].flags if runtime PM is enabled in any case, right?

Yes. It was not plan to behave like this and is fixed, thanks.

> [cut]
> 
>> diff --git a/drivers/tty/serial/8250/Makefile b/drivers/tty/serial/8250/Makefile
>> index 36d68d0..4bac392 100644
>> --- a/drivers/tty/serial/8250/Makefile
>> +++ b/drivers/tty/serial/8250/Makefile
>> @@ -20,3 +20,4 @@ obj-$(CONFIG_SERIAL_8250_HUB6)		+= 8250_hub6.o
>>  obj-$(CONFIG_SERIAL_8250_FSL)		+= 8250_fsl.o
>>  obj-$(CONFIG_SERIAL_8250_DW)		+= 8250_dw.o
>>  obj-$(CONFIG_SERIAL_8250_EM)		+= 8250_em.o
>> +obj-$(CONFIG_SERIAL_8250_OMAP)		+= 8250_omap.o
>> diff --git a/include/uapi/linux/serial_core.h b/include/uapi/linux/serial_core.h
>> index 5820269..74f9b11 100644
>> --- a/include/uapi/linux/serial_core.h
>> +++ b/include/uapi/linux/serial_core.h
>> @@ -54,7 +54,8 @@
>>  #define PORT_ALTR_16550_F32 26	/* Altera 16550 UART with 32 FIFOs */
>>  #define PORT_ALTR_16550_F64 27	/* Altera 16550 UART with 64 FIFOs */
>>  #define PORT_ALTR_16550_F128 28 /* Altera 16550 UART with 128 FIFOs */
>> -#define PORT_MAX_8250	28	/* max port ID */
>> +#define PORT_OMAP_16750	29	/* TI's OMAP internal 16C750 compatible UART */
>> +#define PORT_MAX_8250	29	/* max port ID */
> 
> So in this case I see no reason for new type.

gone.

> 
> Cheers,
> 


Sebastian
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