linux-kernel - Re: mc13xxx-core: kernel hangs after 'regmap

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Message-ID: <20120524121451.GL5361@opensource.wolfsonmicro.com>
Date:	Thu, 24 May 2012 13:14:52 +0100
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Marc Reilly <marc@...esign.com.au>
Cc:	Shawn Guo <shawn.guo@...escale.com>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Sascha Hauer <kernel@...gutronix.de>,
	Philippe Rétornaz <philippe.retornaz@...l.ch>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: mc13xxx-core: kernel hangs after 'regmap_read'

On Thu, May 24, 2012 at 09:22:29PM +1000, Marc Reilly wrote:

> > > 	map->reg_shift = config->pad_bits % 8;
> > > 	map->format.buf_size = (config->reg_bits
> > > 	
> > >                           + config->val_bits
> > > 					         
> > > 					         + map->reg_shift) / 8;

> > Yes, that's been missed in the addition of padding.  We should also be
> > using DIV_ROUND_UP() which we aren't at the minute.  

> That would break, in _regmap_read_raw():

> 	ret = map->bus->read(map->bus_context, map->work_buf,
> 			     map->format.reg_bytes + map->format.pad_bytes,
> 			     val, val_len);

> If pad_bytes was 1 here, then the register size would end up being 2 bytes.

The above is about buf_size...  pad_bytes isn't in the quoted text which
is the issue.

> The way I understood the pad_bytes field was it was the number of _complete_ 
> padding bytes (ie, full 8 bits) between the register address and value. Any 
> remainder of padding bits is incorporated into the register and shifted by 
> shift bits.

Yes.

> > We could also do
> > reg_bytes + pad_bytes + val_bytes which should cover everything I think?

> If we want to cover everything, we could do reg_bytes + pad_bytes + val_bytes 
> + 3 ... :) (I'm not seriously suggesting that).

Yes, but the above should be the total that goes onto the wire.
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