linux-kernel - RE: [PATCH 02/18] DMAENGINE: ste_dma40: only write phy channel config first time

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Date:	Mon, 14 Jun 2010 18:39:15 +0200
From:	Linus WALLEIJ <linus.walleij@...ricsson.com>
To:	Dan Williams <dan.j.williams@...el.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jonas ABERG <jonas.aberg@...ricsson.com>
Subject: RE: [PATCH 02/18] DMAENGINE: ste_dma40: only write phy channel
 config 	first time

Thanks Dan,

Is it OK that we send a new version of the entire patch set trying
to address all comments? (Then hopefully you can merge forward
through the set until there is some further issue.)

On 06/12/2010 12:23 AM, Dan Williams wrote:
> On Tue, Jun 1, 2010 at 5:20 AM, Linus Walleij 
> <linus.walleij@...ricsson.com> wrote:
>> We only need to write the configuration to a physical channel if it 
>> is free, else it is already written.
>>
>> Signed-off-by: Jonas Aaberg <jonas.aberg@...ricsson.com>
>> Signed-off-by: Linus Walleij <linus.walleij@...ricsson.com>
>> ---
>>  drivers/dma/ste_dma40.c |   19 +++++++++++++------
>>  1 files changed, 13 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/dma/ste_dma40.c b/drivers/dma/ste_dma40.c index 
>> 4618d6c..1cd1ff7 100644
>> --- a/drivers/dma/ste_dma40.c
>> +++ b/drivers/dma/ste_dma40.c
>> @@ -1211,9 +1211,9 @@ out:
>>  }
>>
>>  static int d40_config_chan(struct d40_chan *d40c,
>> -                          struct stedma40_chan_cfg *info)
>> +                          struct stedma40_chan_cfg *info,
>> +                          bool is_free_phy)
>>  {
>> -
>>        /* Fill in basic CFG register values */
>>        d40_phy_cfg(&d40c->dma_cfg, &d40c->src_def_cfg,
>>                    &d40c->dst_def_cfg, d40c->log_num != 
>> D40_PHY_CHAN); @@ -1230,8 +1230,14 @@ static int d40_config_chan(struct d40_chan *d40c,
>>                                d40c->dma_cfg.dst_dev_type * 32 + 16;
>>        }
>>
>> -       /* Write channel configuration to the DMA */
>> -       return d40_config_write(d40c);
>> +       /*
>> +        * Only write channel configuration to the DMA if the physical
>> +        * resource is free. In case of multiple logical channels
>> +        * on the same physical resource, only the first write is necessary.
>> +        */
>> +       if (is_free_phy)
>> +               return d40_config_write(d40c);
>> +       return 0;
>>  }
>>
>>  static int d40_config_memcpy(struct d40_chan *d40c) @@ -1691,7 
>> +1697,7 @@ static int d40_alloc_chan_resources(struct dma_chan *chan)
>>        unsigned long flags;
>>        struct d40_chan *d40c =
>>                container_of(chan, struct d40_chan, chan);
>> -
>> +       bool is_free_phy;
>>        spin_lock_irqsave(&d40c->lock, flags);
>>
>>        d40c->completed = chan->cookie = 1; @@ -1705,6 +1711,7 @@ 
>> static int d40_alloc_chan_resources(struct dma_chan *chan)
>>                if (err)
>>                        goto err_alloc;
>>        }
>> +       is_free_phy = (d40c->phy_chan == NULL);
>>
> 
> It seems like d40_config_chan() just wants to be open coded in 
> d40_alloc_chan_resources().  It does not have its own local variables, 
> and the only thing that returns an error is d40_config_write().

True. There are a few more such smaller functions that shall be removed. 
I will do the clean up in a second version of this patch set, ok? 

> 
> While trying to figure out why this flag was needed I happened to 
> notice a gratuitous use of gotos in d40_allocate_channel().  Can we 
> make this function easier to read by just returning -EINVAL directly 
> when those tests fail?

We'll try to see if I can make this function easier to read with less gotos.

Yours,
Linus Walleij
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