linux-kernel - Re: [PATCH] input/spi: add ads7843 support to ads7846 touchscreen driver

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Date:	Mon, 19 Feb 2007 13:48:01 +0100
From:	Nicolas Ferre <nicolas.ferre@....atmel.com>
To:	David Brownell <david-b@...bell.net>, linux-kernel@...r.kernel.org
CC:	Patrice Vilchez <patrice.vilchez@....atmel.com>,
	Andrew Victor <andrew@...people.com>
Subject: Re: [PATCH] input/spi: add ads7843 support to ads7846 touchscreen driver

David Brownell :
> Did you find out what was causing the jerky behavior (draw a circle,
> it looks like a square) before?

No, my previous rework based on your patches (2.6.19) had this
jerky behavior. I was obliged to go back to old style timers.
On this build, with the htimer framework, it seems ok.
  
>> -	/* maybe off internal vREF */
>> -	if (use_internal) {
> 
> This part doesn't make sense.  Could you say what you're trying
> to do?  The ads7846 requres an external vREF.  Is the issue that
> maybe the REF_OFF command isn't just turning off the (non-existent)
> internal voltage reference?  If so the comments need updating, and
> maybe the name REF_OFF needs to change too...

Well, on the ads7843, this command allow to put converter in low power
mode and, more important, enable the PENIRQ (otherwise disabled).

The REF_OFF command can be replaced by the PWRDOWN one (exactly the
same command). This last name matches better the ads7843
datasheet description (and seems ok considering the ads7846 one).

>> -		req->ref_off = REF_OFF;
>> -		req->xfer[4].tx_buf = &req->ref_off;
>> -		req->xfer[4].len = 1;
>> -		spi_message_add_tail(&req->xfer[4], &req->msg);
>> -
>> -		req->xfer[5].rx_buf = &req->scratch;
>> -		req->xfer[5].len = 2;
>> -		CS_CHANGE(req->xfer[5]);
>> -		spi_message_add_tail(&req->xfer[5], &req->msg);
>> -	}
>> +	req->ref_off = REF_OFF;
>> +	req->xfer[4].tx_buf = &req->ref_off;
>> +	req->xfer[4].len = 1;
>> +	spi_message_add_tail(&req->xfer[4], &req->msg);
>> +
>> +	req->xfer[5].rx_buf = &req->scratch;
>> +	req->xfer[5].len = 2;
>> +	CS_CHANGE(req->xfer[5]);
>> +	spi_message_add_tail(&req->xfer[5], &req->msg);
>>  
>>  	ts->irq_disabled = 1;
>>  	disable_irq(spi->irq);

Regards,
-- 
Nicolas Ferre


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