Message-ID: <56700A45.3070109@arm.com>
Date: Tue, 15 Dec 2015 12:40:37 +0000
From: Vladimir Murzin <vladimir.murzin@arm.com>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0
MIME-Version: 1.0
To: Andy Shevchenko <andy.shevchenko@gmail.com>
CC: Arnd Bergmann <arnd@arndb.de>, Russell King <linux@arm.linux.org.uk>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        =?UTF-8?B?VXdlIEtsZWluZS1Lw7ZuaWc=?= 
	<u.kleine-koenig@pengutronix.de>,
        =?UTF-8?B?QW5kcmVhcyBGw6RyYmVy?= <afaerber@suse.de>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        Mark Rutland <Mark.Rutland@arm.com>, Pawel Moll <Pawel.Moll@arm.com>,
        ijc+devicetree <ijc+devicetree@hellion.org.uk>,
        Kumar Gala <galak@codeaurora.org>, Jiri Slaby <jslaby@suse.cz>,
        Rob Herring <robh+dt@kernel.org>,
        devicetree <devicetree@vger.kernel.org>,
        "linux-serial@vger.kernel.org" <linux-serial@vger.kernel.org>,
        "linux-api@vger.kernel.org" <linux-api@vger.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v1 04/10] serial: mps2-uart: add MPS2 UART driver
References: <1449048790-25859-1-git-send-email-vladimir.murzin@arm.com>	<1449048790-25859-5-git-send-email-vladimir.murzin@arm.com> <CAHp75Vd98TEQ7TiD==t=RgYOqSinWgnyRjg7V=oPXmEx0nedLQ@mail.gmail.com>
In-Reply-To: <CAHp75Vd98TEQ7TiD==t=RgYOqSinWgnyRjg7V=oPXmEx0nedLQ@mail.gmail.com>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 3439
Lines: 119

On 12/12/15 23:39, Andy Shevchenko wrote:
> On Wed, Dec 2, 2015 at 11:33 AM, Vladimir Murzin
> <vladimir.murzin@arm.com> wrote:
>> This driver adds support to the UART controller found on ARM MPS2
>> platform.
> 
> Just few comments (have neither time not big desire to do full review).
> 

Still better than nothing ;) I'm mostly agree on points you had, so I've
just left some I'm doubt about...

>> +
>> +static void mps2_uart_enable_ms(struct uart_port *port)
>> +{
>> +}
>> +
>> +static void mps2_uart_break_ctl(struct uart_port *port, int ctl)
>> +{
>> +}
> 
> Are those required to be present? If not, remove them until you have
> alive code there.

A quick grep shows that core calls mps2_uart_break_ctl()
unconditionally, but, yes, it checks for presence of
mps2_uart_enable_ms() before jumping there, so it is safe to remove latter.

>> +static irqreturn_t mps2_uart_oerrirq(int irq, void *data)
>> +{
>> +       irqreturn_t handled = IRQ_NONE;
>> +       struct uart_port *port = data;
>> +       u8 irqflag = mps2_uart_read8(port, UARTn_INT);
>> +
>> +       spin_lock(&port->lock);
>> +
>> +       if (irqflag & UARTn_INT_RX_OVERRUN) {
>> +               struct tty_port *tport = &port->state->port;
>> +
>> +               mps2_uart_write8(port, UARTn_INT_RX_OVERRUN, UARTn_INT);
>> +               tty_insert_flip_char(tport, 0, TTY_OVERRUN);
>> +               port->icount.overrun++;
>> +               handled = IRQ_HANDLED;
>> +       }
>> +
>> +       /* XXX: this shouldn't happen? */
> 
> If shouldn't why it's there? Otherwise better to explain which
> conditions may lead to this.
> 

In practice I've never seen that happened and I think it never *should*
happen since we check if there is room in TX buffer. However, I could be
wrong here, so it is why that statement has question mark.

>> +       if (irqflag & UARTn_INT_TX_OVERRUN) {
>> +               mps2_uart_write8(port, UARTn_INT_TX_OVERRUN, UARTn_INT);
>> +               handled = IRQ_HANDLED;
>> +       }
>> +
>> +       spin_unlock(&port->lock);
>> +
>> +       return handled;
>> +}
>> +
...
>> +static void mps2_uart_release_port(struct uart_port *port)
>> +{
>> +}
>> +
>> +static int mps2_uart_request_port(struct uart_port *port)
>> +{
>> +       return 0;
>> +}
>> +
> 
> Same question about empty stubs.

Looks like they called unconditionally by the core.

>> +static int __init mps2_uart_init(void)
>> +{
>> +       int ret;
>> +
>> +       ret = uart_register_driver(&mps2_uart_driver);
>> +       if (ret)
>> +               return ret;
>> +
>> +       ret = platform_driver_register(&mps2_serial_driver);
>> +       if (ret)
>> +               uart_unregister_driver(&mps2_uart_driver);
>> +
>> +       pr_info("MPS2 UART driver initialized\n");
>> +
>> +       return ret;
>> +}
>> +module_init(mps2_uart_init);
>> +
>> +static void __exit mps2_uart_exit(void)
>> +{
>> +       platform_driver_unregister(&mps2_serial_driver);
>> +       uart_unregister_driver(&mps2_uart_driver);
>> +}
>> +module_exit(mps2_uart_exit);
> 
> module_platform_driver();
> And move uart_*register calls to probe/remove.
> 

With this move we'll get uart_*register for every device probed, no?

Thanks
Vladimir

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/