linux-kernel - Re: [PATCH v9 12/16] serial: amba-pl011: Pass FIQ information to KGDB.

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Message-ID: <53F313F2.6090103@linaro.org>
Date:	Tue, 19 Aug 2014 10:08:02 +0100
From:	Daniel Thompson <daniel.thompson@...aro.org>
To:	Peter Hurley <peter@...leysoftware.com>,
	Russell King <linux@....linux.org.uk>
CC:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	kgdb-bugreport@...ts.sourceforge.net, patches@...aro.org,
	linaro-kernel@...ts.linaro.org,
	John Stultz <john.stultz@...aro.org>,
	Anton Vorontsov <anton.vorontsov@...aro.org>,
	Colin Cross <ccross@...roid.com>, kernel-team@...roid.com,
	Rob Herring <robherring2@...il.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Ben Dooks <ben.dooks@...ethink.co.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Dave Martin <Dave.Martin@....com>,
	Fabio Estevam <festevam@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Nicolas Pitre <nico@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>, linux-serial@...r.kernel.org
Subject: Re: [PATCH v9 12/16] serial: amba-pl011: Pass FIQ information to
 KGDB.

On 18/08/14 19:30, Peter Hurley wrote:
> Hi Daniel,
> 
> On 08/18/2014 10:28 AM, Daniel Thompson wrote:
>> Speculatively register a FIQ resource with KGDB. KGDB will only
>> accept it if the kgdb/fiq feature is enabled (both with compile time and
>> runtime switches) and the interrupt controller supports FIQ.
>>
>> By providing this information to KGDB the serial driver offers
>> "permission" for KGDB to route the UART interrupt signal from the
>> drivers own handler to KGDBs FIQ handler (which will eventually use the
>> UART's polled I/O callbacks to interact with the user). This permission
>> also implies the amba-pl011 driver has already unmasked RX interrupts
>> (otherwise the FIQ handler will never trigger).
>>
>> Signed-off-by: Daniel Thompson <daniel.thompson@...aro.org>
>> Cc: Russell King <linux@....linux.org.uk>
>> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> Cc: Jiri Slaby <jslaby@...e.cz>
>> Cc: linux-serial@...r.kernel.org
>> ---
>>  drivers/tty/serial/amba-pl011.c | 94 ++++++++++++++++++++++++-----------------
>>  1 file changed, 55 insertions(+), 39 deletions(-)#

Thanks for the review.


>> diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
>> index 8572f2a..ec8ddc7 100644
>> --- a/drivers/tty/serial/amba-pl011.c
>> +++ b/drivers/tty/serial/amba-pl011.c
>> @@ -58,6 +58,7 @@
>>  #include <linux/pinctrl/consumer.h>
>>  #include <linux/sizes.h>
>>  #include <linux/io.h>
>> +#include <linux/kgdb.h>
>>  
>>  #define UART_NR			14
>>  
>> @@ -1416,8 +1417,61 @@ static void pl011_break_ctl(struct uart_port *port, int break_state)
>>  	spin_unlock_irqrestore(&uap->port.lock, flags);
>>  }
>>  
> 
> Is pl011_hwinit() just being relocated in source to avoid the forward
> declaration? If so, this is usually split into its own commit.

Ok. I'll do this.


>> +static int pl011_hwinit(struct uart_port *port)
>> +{
>> +	struct uart_amba_port *uap = (struct uart_amba_port *)port;
>> +	int retval;
>> +
>> +	/* Optionaly enable pins to be muxed in and configured */
>> +	pinctrl_pm_select_default_state(port->dev);
>> +
>> +	/*
>> +	 * Try to enable the clock producer.
>> +	 */
>> +	retval = clk_prepare_enable(uap->clk);
>> +	if (retval)
>> +		return retval;
>> +
>> +	uap->port.uartclk = clk_get_rate(uap->clk);
>> +
>> +	/* Clear pending error and receive interrupts */
>> +	writew(UART011_OEIS | UART011_BEIS | UART011_PEIS | UART011_FEIS |
>> +	       UART011_RTIS | UART011_RXIS, uap->port.membase + UART011_ICR);
>> +
>> +	/*
>> +	 * Save interrupts enable mask, and enable RX interrupts in case if
>> +	 * the interrupt is used for NMI entry.
>> +	 */
>> +	uap->im = readw(uap->port.membase + UART011_IMSC);
>> +	writew(UART011_RTIM | UART011_RXIM, uap->port.membase + UART011_IMSC);
>> +
>> +	if (dev_get_platdata(uap->port.dev)) {
>> +		struct amba_pl011_data *plat;
>> +
>> +		plat = dev_get_platdata(uap->port.dev);
>> +		if (plat->init)
>> +			plat->init();
>> +	}
>> +	return 0;
>> +}
>> +
>>  #ifdef CONFIG_CONSOLE_POLL
>>  
>> +static int pl011_poll_init(struct uart_port *port)
>> +{
>> +	struct uart_amba_port *uap = (struct uart_amba_port *)port;
> 
> Please use container_of() in new code.

Ok.

Personally I dislike a file that mixes casts and conatiner_of but I
guess I can make both of us happy by switching the whole driver to
container_of. Separate patch again?


>> +	int retval;
>> +
>> +	retval = pl011_hwinit(port);
>> +
>> +#ifdef CONFIG_KGDB_FIQ
>> +	if (retval == 0)
>> +		kgdb_register_fiq(uap->port.irq);
> 
> The uap->port dereference is unnecessary since the port parameter
> is the same thing.
> 
> 		kgdb_register_fiq(port->irq);

Ok.

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