linux-kernel - Re: [PATCH 24/32 v2] dmaengine: ste_dma40: Supply full Device Tree parsing support

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Message-ID: <20130418134316.GA3959@gmail.com>
Date:	Thu, 18 Apr 2013 14:43:16 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linus.walleij@...ricsson.com, Vinod Koul <vinod.koul@...el.com>,
	Dan Williams <djbw@...com>,
	Per Forlin <per.forlin@...ricsson.com>,
	Rabin Vincent <rabin@....in>
Subject: Re: [PATCH 24/32 v2] dmaengine: ste_dma40: Supply full Device Tree
 parsing support

On Thu, 18 Apr 2013, Arnd Bergmann wrote:

> On Thursday 18 April 2013, Lee Jones wrote:
> > +Clients
> > +Required properties:
> > +- dmas: Comma separated list of dma channel requests
> > +- dma-names: Names of the aforementioned requested channels
> > +
> > +Each dmas request consists of 4 cells:
> > +  1. A phandle pointing to the DMA controller
> > +  2. Device Type
> > +  3. The DMA request line number (only when 'use fixed channel' is set)
> > +  4. A 32bit mask specifying; mode, direction and endianess [NB: This list will grow]
> > +        bit 1: Mode:
> > +           0: Logical
> > +           1: Physical
> > +        bit 2: Direction:
> > +           0: Mem to Mem
> > +           1: Mem to Dev
> 
> You probably mean 
> 
> 		0: Dev to mem
> 
> Related to this, I would recommend not listing bit numbers like this, since there
> is some amount of confusion regarding how they are counted: zero-based on one-based
> and LSB-to-MSB or MSB-to-LSB
> 
> You can completely avoid this problem by listing them as bit masks:
> 
> 	0x00000002:
> 		Logical channel when unset
> 		Physical channel when set
> 	0x00000004:
> 		Direction from device when unset
> 		Direction to device when unset
> 	... 
> 
> > +		dmas = <&dma 13 0 0x8>, /* Logical - DevToMem */
> > +		       <&dma 13 0 0x4>; /* Logical - MemToDev */
> 
> The bit in the example no longer matches the description.
> 
> > +
> > +	switch (D40_DT_FLAGS_DIR(flags)) {
> > +	case 0: cfg.dir = STEDMA40_MEM_TO_MEM; break;
> > +	case 1: cfg.dir = STEDMA40_MEM_TO_PERIPH; break;
> > +	}
> 
> Same typo above.
> 
> > +	if (cfg.dir == STEDMA40_PERIPH_TO_MEM)
> > +		cfg.src_info.big_endian = D40_DT_FLAGS_BIG_ENDIAN(flags);
> > +	if (cfg.dir == STEDMA40_MEM_TO_PERIPH)
> > +		cfg.dst_info.big_endian = D40_DT_FLAGS_BIG_ENDIAN(flags);
> 
> You can fold these two into the switch statement above.

This is what happens when you rush a fixup. :)

I'll do it properly now.

-- 
Lee Jones
Linaro ST-Ericsson Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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