LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: David Engraf <david.engraf@sysgo.com>
To: Ludovic Desroches <ludovic.desroches@microchip.com>
Cc: nicolas.ferre@microchip.com, alexandre.belloni@bootlin.com,
	linux-i2c@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] i2c: at91: Read all available bytes at once
Date: Thu, 26 Apr 2018 07:52:17 +0200	[thread overview]
Message-ID: <ddc4beb3-5620-dc69-5b16-bce2737fb59f@sysgo.com> (raw)
In-Reply-To: <20180425150853.GU13305@rfolt0960.corp.atmel.com>

Hi Ludovic,

Am 25.04.2018 um 17:08 schrieb Ludovic Desroches:
> Hi David,
> 
> On Wed, Apr 18, 2018 at 02:40:55PM +0200, David Engraf wrote:
>> With FIFO enabled it is possible to read multiple bytes
>> at once in the interrupt handler as long as RXRDY is
>> set. This may also reduce the number of interrupts.
>>
>> Signed-off-by: David Engraf <david.engraf@sysgo.com>
>> ---
>>   drivers/i2c/busses/i2c-at91.c | 8 ++++++--
>>   1 file changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c
>> index bfd1fdff64a9..d01c2b2384bd 100644
>> --- a/drivers/i2c/busses/i2c-at91.c
>> +++ b/drivers/i2c/busses/i2c-at91.c
>> @@ -518,8 +518,12 @@ static irqreturn_t atmel_twi_interrupt(int irq, void *dev_id)
>>   	 * the RXRDY interrupt first in order to not keep garbage data in the
>>   	 * Receive Holding Register for the next transfer.
>>   	 */
>> -	if (irqstatus & AT91_TWI_RXRDY)
>> -		at91_twi_read_next_byte(dev);
>> +	if (irqstatus & AT91_TWI_RXRDY) {
>> +		/* read all available bytes at once when FIFO is used */
>> +		do {
>> +			at91_twi_read_next_byte(dev);
>> +		} while (at91_twi_read(dev, AT91_TWI_SR) & AT91_TWI_RXRDY);
> 
> You can avoid this check by using the RXFL field to know the number of
> data you can read. Did you try to use it? If yes, did you notice some issues?

I did a quick test by reading RXFL and it worked as well but I decided 
to use the more readable solution by polling RXRDY. Also I don't need to 
check if the FIFO has been enabled.

If you prefer using RXFL I can create a new patch.

Best regards
- David


> Regards
> 
> Ludovic
> 
>> +	}
>>   
>>   	/*
>>   	 * When a NACK condition is detected, the I2C controller sets the NACK,
>> -- 
>> 2.14.1
>>

-- 
Mit freundlichen Grüßen/Best regards,

David Engraf
Product Engineer

SYSGO AG
Office Mainz
Am Pfaffenstein 14 / D-55270 Klein-Winternheim / Germany

Phone: +49-6136-9948-0 / Fax: +49-6136-9948-10
E-mail: david.engraf@sysgo.com
_________________________________________________________________________________

Web: https://www.sysgo.com
Blog: https://www.sysgo.com/blog
Events: https://www.sysgo.com/events
Newsletter: https://www.sysgo.com/newsletter
_________________________________________________________________________________

Handelsregister/Commercial Registry: HRB Mainz 90 HRB 8066
Vorstand/Executive Board: Etienne Butery (CEO), Kai Sablotny (COO)
Aufsichtsratsvorsitzender/Supervisory Board Chairman: Marc Darmon
USt-Id-Nr./VAT-Id-No.: DE 149062328

      parent reply	other threads:[~2018-04-26  5:52 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-18 12:40 David Engraf
2018-04-25 15:08 ` Ludovic Desroches
2018-04-25 15:43   ` David Engraf
2018-04-26  8:25     ` Ludovic Desroches
2018-04-26  9:53       ` [PATCH v2] " David Engraf
2018-04-26 12:30         ` Ludovic Desroches
2018-04-28 12:38         ` Wolfram Sang
2018-04-30  6:11           ` David Engraf
2018-04-26  5:52   ` David Engraf [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=ddc4beb3-5620-dc69-5b16-bce2737fb59f@sysgo.com \
    --to=david.engraf@sysgo.com \
    --cc=alexandre.belloni@bootlin.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-i2c@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=ludovic.desroches@microchip.com \
    --cc=nicolas.ferre@microchip.com \
    --subject='Re: [PATCH] i2c: at91: Read all available bytes at once' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).