Re: [PATCH v5 5/5] tty/serial: Add Spreadtrum sc9836-uart driver support

From: Lyra Zhang
Date: Mon Jan 19 2015 - 04:55:20 EST

On Sat, Jan 17, 2015 at 12:41 AM, Rob Herring <robherring2@xxxxxxxxx> wrote:
> On Fri, Jan 16, 2015 at 4:00 AM, Chunyan Zhang
> <chunyan.zhang@xxxxxxxxxxxxxx> wrote:
>> Add a full sc9836-uart driver for SC9836 SoC which is based on the
>> spreadtrum sharkl64 platform.
>> This driver also support earlycon.
>> This patch also replaced the spaces between the macros and their
>> values with the tabs in serial_core.h
>>
>> Signed-off-by: Chunyan Zhang <chunyan.zhang@xxxxxxxxxxxxxx>
>> Signed-off-by: Orson Zhai <orson.zhai@xxxxxxxxxxxxxx>
>> Originally-by: Lanqing Liu <lanqing.liu@xxxxxxxxxxxxxx>
>> ---
>> drivers/tty/serial/Kconfig | 18 +
>> drivers/tty/serial/Makefile | 1 +
>> drivers/tty/serial/sprd_serial.c | 772 ++++++++++++++++++++++++++++++++++++++
>> include/uapi/linux/serial_core.h | 3 +
>> 4 files changed, 794 insertions(+)
>> create mode 100644 drivers/tty/serial/sprd_serial.c
>>
>> diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
>> index c79b43c..969d3cd 100644
>> --- a/drivers/tty/serial/Kconfig
>> +++ b/drivers/tty/serial/Kconfig
>> @@ -1577,6 +1577,24 @@ config SERIAL_MEN_Z135
>> This driver can also be build as a module. If so, the module will be called
>> men_z135_uart.ko
>>
>> +config SERIAL_SPRD
>> + tristate "Support for SPRD serial"
>
> Can the menu text spell out Spreadtrum. What SPRD means is not obvious.
>

Ok, I'll address it.

>> + depends on ARCH_SPRD
>> + select SERIAL_CORE
>> + help
>> + This enables the driver for the Spreadtrum's serial.
>> +
>> +config SERIAL_SPRD_CONSOLE
>> + bool "SPRD UART console support"
>
> Same here.
>
>> + depends on SERIAL_SPRD=y
>> + select SERIAL_CORE_CONSOLE
>> + select SERIAL_EARLYCON
>> + help
>> + Support for early debug console using Spreadtrum's serial. This enables
>> + the console before standard serial driver is probed. This is enabled
>> + with "earlycon" on the kernel command line. The console is
>> + enabled when early_param is processed.
>> +
>> endmenu
>>
>> config SERIAL_MCTRL_GPIO
>> diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile
>> index 9a548ac..4801aca 100644
>> --- a/drivers/tty/serial/Makefile
>> +++ b/drivers/tty/serial/Makefile
>> @@ -93,6 +93,7 @@ obj-$(CONFIG_SERIAL_ARC) += arc_uart.o
>> obj-$(CONFIG_SERIAL_RP2) += rp2.o
>> obj-$(CONFIG_SERIAL_FSL_LPUART) += fsl_lpuart.o
>> obj-$(CONFIG_SERIAL_MEN_Z135) += men_z135_uart.o
>> +obj-$(CONFIG_SERIAL_SPRD) += sprd_serial.o
>>
>> # GPIOLIB helpers for modem control lines
>> obj-$(CONFIG_SERIAL_MCTRL_GPIO) += serial_mctrl_gpio.o
>> diff --git a/drivers/tty/serial/sprd_serial.c b/drivers/tty/serial/sprd_serial.c
>> new file mode 100644
>> index 0000000..81839e4
>> --- /dev/null
>> +++ b/drivers/tty/serial/sprd_serial.c
>> @@ -0,0 +1,772 @@
>> +/*
>> + * Copyright (C) 2012 Spreadtrum Communications Inc.
>
> This is unchanged in 3 years?
>

ok, I'll change it to 2012-2015.

>> + *
>> + * This software is licensed under the terms of the GNU General Public
>> + * License version 2, as published by the Free Software Foundation, and
>> + * may be copied, distributed, and modified under those terms.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
>> + * GNU General Public License for more details.
>> + */
>> +
>> +#include <linux/clk.h>
>> +#include <linux/console.h>
>> +#include <linux/delay.h>
>> +#include <linux/io.h>
>> +#include <linux/ioport.h>
>> +#include <linux/kernel.h>
>> +#include <linux/module.h>
>> +#include <linux/of.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/serial_core.h>
>> +#include <linux/serial.h>
>> +#include <linux/slab.h>
>> +#include <linux/tty.h>
>> +#include <linux/tty_flip.h>
>> +
>> +/* device name */
>> +#define UART_NR_MAX 8
>> +#define SPRD_TTY_NAME "ttySPX"
>
> We really want to get away from per SOC serial names and use ttyS for
> serial port /dev names. There's issues switching existing drivers
> because this creates an ABI, so we can only have new drivers follow
> this.
>

ok. i see. I'll convert it to ttyS in the next version.

> [...]
>
>> +static struct platform_driver sprd_platform_driver = {
>> + .probe = sprd_probe,
>> + .remove = sprd_remove,
>> + .driver = {
>> + .name = "sprd_serial",
>> + .of_match_table = of_match_ptr(serial_ids),
>> + .pm = &sprd_pm_ops,
>> + },
>> +};
>> +
>> +static int __init sprd_serial_init(void)
>> +{
>> + int ret = 0;
>> +
>> + ret = uart_register_driver(&sprd_uart_driver);
>
> This can be done in probe now. Then you can use module_platform_driver().
>

Question:
1. there are 4 uart ports configured in dt for sprd_serial, so probe
will be called 4 times, but uart_register_driver only needs to be
called one time, so can we use uart_driver.state to check if
uart_register_driver has already been called ?

2. if I use module_platform_driver() instead of
module_init(sprd_serial_init) and module_exit(sprd_serial_exit) , I
must move uart_unregister_driver() which is now processed in
sprd_serial_exit() to sprd_remove(), there is a similar problem with
probe(), sprd_remove() will also be called 4 times, and actually it
should be called only one time. How can we deal with this case?

3. for the second question, we can check the platform_device->id, if
it is equal to the index of last port (e.g. 4 for this case), then
uart_unregister_driver() can be called. Does it work correctly? since
for this case, we must keep the order of releasing ports.


Thanks,
Chunyan


> Rob
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