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staging: comedi: rtd520: add a few comments 

H Hartley Sweeten's recent series of patches to clean up the rtd520
driver made some of the register accesses harder to understand.  Add a
few comments to provide some clues to the reader.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ian Abbott 2012-07-11 13:28:19 +01:00 committed by Greg Kroah-Hartman
parent 3cdefc9276
commit 9a1f72233f
1 changed files with 18 additions and 5 deletions
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23
drivers/staging/comedi/drivers/rtd520.c
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@ -494,6 +494,7 @@ static int rtd520_probe_fifo_depth(struct comedi_device *dev)
writel(0, devpriv->las0 + LAS0_ADC_FIFO_CLEAR);
rtd_load_channelgain_list(dev, 1, &chanspec);
/* ADC conversion trigger source: SOFTWARE */
writel(0, devpriv->las0 + LAS0_ADC_CONVERSION);
/* convert samples */
for (i = 0; i < limit; ++i) {
@ -544,7 +545,7 @@ static int rtd_ai_rinsn(struct comedi_device *dev,
/* write channel to multiplexer and clear channel gain table */
rtd_load_channelgain_list(dev, 1, &insn->chanspec);
/* set conversion source */
/* ADC conversion trigger source: SOFTWARE */
writel(0, devpriv->las0 + LAS0_ADC_CONVERSION);
/* convert n samples */
@ -908,8 +909,9 @@ abortTransfer:
/* fall into transferDone */
transferDone:
/* pacer stop source: SOFTWARE */
writel(0, devpriv->las0 + LAS0_PACER_STOP);
writel(0, devpriv->las0 + LAS0_PACER);
writel(0, devpriv->las0 + LAS0_PACER); /* stop pacer */
writel(0, devpriv->las0 + LAS0_ADC_CONVERSION);
devpriv->intMask = 0;
writew(devpriv->intMask, devpriv->las0 + LAS0_IT);
@ -1180,8 +1182,9 @@ static int rtd_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
int timer;
/* stop anything currently running */
/* pacer stop source: SOFTWARE */
writel(0, devpriv->las0 + LAS0_PACER_STOP);
writel(0, devpriv->las0 + LAS0_PACER);
writel(0, devpriv->las0 + LAS0_PACER); /* stop pacer */
writel(0, devpriv->las0 + LAS0_ADC_CONVERSION);
devpriv->intMask = 0;
writew(devpriv->intMask, devpriv->las0 + LAS0_IT);
@ -1215,12 +1218,17 @@ static int rtd_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
/* setup the common case and override if needed */
if (cmd->chanlist_len > 1) {
/*DPRINTK ("rtd520: Multi channel setup\n"); */
/* pacer start source: SOFTWARE */
writel(0, devpriv->las0 + LAS0_PACER_START);
/* burst trigger source: PACER */
writel(1, devpriv->las0 + LAS0_BURST_START);
/* ADC conversion trigger source: BURST */
writel(2, devpriv->las0 + LAS0_ADC_CONVERSION);
} else { /* single channel */
/*DPRINTK ("rtd520: single channel setup\n"); */
/* pacer start source: SOFTWARE */
writel(0, devpriv->las0 + LAS0_PACER_START);
/* ADC conversion trigger source: PACER */
writel(1, devpriv->las0 + LAS0_ADC_CONVERSION);
}
writel((devpriv->fifoLen / 2 - 1) & 0xffff, devpriv->las0 + LAS0_ACNT);
@ -1269,7 +1277,9 @@ static int rtd_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
devpriv->transCount = 0;
devpriv->flags &= ~SEND_EOS;
}
/* pacer clock source: INTERNAL 8MHz */
writel(1, devpriv->las0 + LAS0_PACER_SELECT);
/* just interrupt, don't stop */
writel(1, devpriv->las0 + LAS0_ACNT_STOP_ENABLE);
/* BUG??? these look like enumerated values, but they are bit fields */
@ -1305,6 +1315,7 @@ static int rtd_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
break;
case TRIG_EXT:
/* pacer start source: EXTERNAL */
writel(1, devpriv->las0 + LAS0_PACER_START);
break;
@ -1327,6 +1338,7 @@ static int rtd_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
break;
case TRIG_EXT: /* external */
/* burst trigger source: EXTERNAL */
writel(2, devpriv->las0 + LAS0_BURST_START);
break;
@ -1378,7 +1390,7 @@ static int rtd_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
/* BUG: start_src is ASSUMED to be TRIG_NOW */
/* BUG? it seems like things are running before the "start" */
readl(devpriv->las0 + LAS0_PACER);
readl(devpriv->las0 + LAS0_PACER); /* start pacer */
return 0;
}
@ -1391,8 +1403,9 @@ static int rtd_ai_cancel(struct comedi_device *dev, struct comedi_subdevice *s)
u32 overrun;
u16 status;
/* pacer stop source: SOFTWARE */
writel(0, devpriv->las0 + LAS0_PACER_STOP);
writel(0, devpriv->las0 + LAS0_PACER);
writel(0, devpriv->las0 + LAS0_PACER); /* stop pacer */
writel(0, devpriv->las0 + LAS0_ADC_CONVERSION);
devpriv->intMask = 0;
writew(devpriv->intMask, devpriv->las0 + LAS0_IT);