> On 18.02.2016, at 04:24, Eric Anholt <eric@xxxxxxxxxx> wrote:
>
> kernel@xxxxxxxxxxxxxxxx writes:
>
>> From: Martin Sperl <kernel@xxxxxxxxxxxxxxxx>
>>
>> In preparation of adding slave_sg functionality this patch moves the
>> generation/allocation of bcm2835_desc and the building of
>> the corresponding DMA-control-block chain from bcm2835_dma_prep_dma_cyclic
>> into the newly created method bcm2835_dma_create_cb_chain.
>>
>> This new code also takes the limits of LITE channels into account
>> and splits the control-block transfers at the correct location.
>>
>> Tested Audio output with a Hifiberry I2S card.
>>
>> Signed-off-by: Martin Sperl <kernel@xxxxxxxxxxxxxxxx>
>> ---
>> drivers/dma/bcm2835-dma.c | 288 ++++++++++++++++++++++++++++++---------------
>> 1 file changed, 191 insertions(+), 97 deletions(-)
>>
>> diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
>> index 43758ba..41a4f0b 100644
>> --- a/drivers/dma/bcm2835-dma.c
>> +++ b/drivers/dma/bcm2835-dma.c
>> @@ -90,12 +90,12 @@ struct bcm2835_desc {
>> struct virt_dma_desc vd;
>> enum dma_transfer_direction dir;
>>
>> - struct bcm2835_cb_entry *cb_list;
>> -
>> unsigned int frames;
>> size_t size;
>>
>> bool cyclic;
>> +
>> + struct bcm2835_cb_entry cb_list[];
>> };
>>
>> #define BCM2835_DMA_CS 0x00
>> @@ -181,6 +181,22 @@ struct bcm2835_desc {
>> #define BCM2835_DMA_IRQ_SHARED 11
>> #define BCM2835_DMA_IRQ_ALL 12
>>
>> +/* the max dma length for different channels */
>> +#define MAX_DMA_LEN SZ_1G
>> +#define MAX_LITE_DMA_LEN (SZ_64K - 4)
>> +
>> +static inline bool bcm2835_dma_is_lite(struct bcm2835_chan *c)
>> +{
>> + /* dma channels >= 7 are LITE channels */
>> + return (c->ch >= 7);
>> +}
>
> You can ask a channel if it's a LITE engine by checking if the DEBUG reg
> has bit 28 set. Then you don't need to have the software/DT guessing
> about it.
I will implement that - it is simple.
> However, I'm disappointed to see these changes for adding LITE support
> included in the same commit as refactoring chain generation into a
> separate function.
I will separate this “LITE-channel handling” out into a separate patch.
Martin
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