Re: [PATCH 5/5] dmaengine: jz4780: Support bidirectional I/O on one channel

[Paul Cercueil <paul@crapouillou.net>]

Hi Vinod,

Le lun., oct. 18 2021 at 12:03:42 +0530, Vinod Koul <vkoul@kernel.org> 
a écrit :
> On 11-10-21, 16:36, Paul Cercueil wrote:
>>  For some devices with only half-duplex capabilities, it doesn't make
>>  much sense to use one DMA channel per direction, as both channels 
>> will
>>  never be active at the same time.
>> 
>>  Add support for bidirectional I/O on DMA channels. The client 
>> drivers
>>  can then request a "tx-rx" DMA channel which will be used for both
>>  directions.
>> 
>>  Signed-off-by: Paul Cercueil <paul@crapouillou.net>
>>  ---
>>   drivers/dma/dma-jz4780.c | 48 
>> ++++++++++++++++++++++++++--------------
>>   1 file changed, 32 insertions(+), 16 deletions(-)
>> 
>>  diff --git a/drivers/dma/dma-jz4780.c b/drivers/dma/dma-jz4780.c
>>  index 4d62e24ebff9..ee1d50792c32 100644
>>  --- a/drivers/dma/dma-jz4780.c
>>  +++ b/drivers/dma/dma-jz4780.c
>>  @@ -122,6 +122,7 @@ struct jz4780_dma_desc {
>>   	dma_addr_t desc_phys;
>>   	unsigned int count;
>>   	enum dma_transaction_type type;
>>  +	uint32_t transfer_type;
> 
> why not u32?

It should be u32 yes. The driver uses uint32_t everywhere so I didn't 
think about it.

> 
>>   	uint32_t status;
>>   };
>> 
>>  @@ -130,7 +131,7 @@ struct jz4780_dma_chan {
>>   	unsigned int id;
>>   	struct dma_pool *desc_pool;
>> 
>>  -	uint32_t transfer_type;
>>  +	uint32_t transfer_type_tx, transfer_type_rx;
>>   	uint32_t transfer_shift;
>>   	struct dma_slave_config	config;
>> 
>>  @@ -157,7 +158,7 @@ struct jz4780_dma_dev {
>>   };
>> 
>>   struct jz4780_dma_filter_data {
>>  -	uint32_t transfer_type;
>>  +	uint32_t transfer_type_tx, transfer_type_rx;
>>   	int channel;
>>   };
>> 
>>  @@ -226,9 +227,10 @@ static inline void 
>> jz4780_dma_chan_disable(struct jz4780_dma_dev *jzdma,
>>   		jz4780_dma_ctrl_writel(jzdma, JZ_DMA_REG_DCKEC, BIT(chn));
>>   }
>> 
>>  -static struct jz4780_dma_desc *jz4780_dma_desc_alloc(
>>  -	struct jz4780_dma_chan *jzchan, unsigned int count,
>>  -	enum dma_transaction_type type)
>>  +static struct jz4780_dma_desc *
>>  +jz4780_dma_desc_alloc(struct jz4780_dma_chan *jzchan, unsigned int 
>> count,
>>  +		      enum dma_transaction_type type,
>>  +		      enum dma_transfer_direction direction)
>>   {
>>   	struct jz4780_dma_desc *desc;
>> 
>>  @@ -248,6 +250,12 @@ static struct jz4780_dma_desc 
>> *jz4780_dma_desc_alloc(
>> 
>>   	desc->count = count;
>>   	desc->type = type;
>>  +
>>  +	if (direction == DMA_DEV_TO_MEM)
>>  +		desc->transfer_type = jzchan->transfer_type_rx;
>>  +	else
>>  +		desc->transfer_type = jzchan->transfer_type_tx;
>>  +
>>   	return desc;
>>   }
>> 
>>  @@ -361,7 +369,7 @@ static struct dma_async_tx_descriptor 
>> *jz4780_dma_prep_slave_sg(
>>   	unsigned int i;
>>   	int err;
>> 
>>  -	desc = jz4780_dma_desc_alloc(jzchan, sg_len, DMA_SLAVE);
>>  +	desc = jz4780_dma_desc_alloc(jzchan, sg_len, DMA_SLAVE, 
>> direction);
>>   	if (!desc)
>>   		return NULL;
>> 
>>  @@ -410,7 +418,7 @@ static struct dma_async_tx_descriptor 
>> *jz4780_dma_prep_dma_cyclic(
>> 
>>   	periods = buf_len / period_len;
>> 
>>  -	desc = jz4780_dma_desc_alloc(jzchan, periods, DMA_CYCLIC);
>>  +	desc = jz4780_dma_desc_alloc(jzchan, periods, DMA_CYCLIC, 
>> direction);
>>   	if (!desc)
>>   		return NULL;
>> 
>>  @@ -455,14 +463,14 @@ static struct dma_async_tx_descriptor 
>> *jz4780_dma_prep_dma_memcpy(
>>   	struct jz4780_dma_desc *desc;
>>   	uint32_t tsz;
>> 
>>  -	desc = jz4780_dma_desc_alloc(jzchan, 1, DMA_MEMCPY);
>>  +	desc = jz4780_dma_desc_alloc(jzchan, 1, DMA_MEMCPY, 0);
>>   	if (!desc)
>>   		return NULL;
>> 
>>   	tsz = jz4780_dma_transfer_size(jzchan, dest | src | len,
>>   				       &jzchan->transfer_shift);
>> 
>>  -	jzchan->transfer_type = JZ_DMA_DRT_AUTO;
>>  +	desc->transfer_type = JZ_DMA_DRT_AUTO;
>> 
>>   	desc->desc[0].dsa = src;
>>   	desc->desc[0].dta = dest;
>>  @@ -528,7 +536,7 @@ static void jz4780_dma_begin(struct 
>> jz4780_dma_chan *jzchan)
>> 
>>   	/* Set transfer type. */
>>   	jz4780_dma_chn_writel(jzdma, jzchan->id, JZ_DMA_REG_DRT,
>>  -			      jzchan->transfer_type);
>>  +			      jzchan->desc->transfer_type);
>> 
>>   	/*
>>   	 * Set the transfer count. This is redundant for a 
>> descriptor-driven
>>  @@ -788,7 +796,8 @@ static bool jz4780_dma_filter_fn(struct 
>> dma_chan *chan, void *param)
>>   		return false;
>>   	}
>> 
>>  -	jzchan->transfer_type = data->transfer_type;
>>  +	jzchan->transfer_type_tx = data->transfer_type_tx;
>>  +	jzchan->transfer_type_rx = data->transfer_type_rx;
>> 
>>   	return true;
>>   }
>>  @@ -800,11 +809,17 @@ static struct dma_chan 
>> *jz4780_of_dma_xlate(struct of_phandle_args *dma_spec,
>>   	dma_cap_mask_t mask = jzdma->dma_device.cap_mask;
>>   	struct jz4780_dma_filter_data data;
>> 
>>  -	if (dma_spec->args_count != 2)
>>  +	if (dma_spec->args_count == 2) {
>>  +		data.transfer_type_tx = dma_spec->args[0];
>>  +		data.transfer_type_rx = dma_spec->args[0];
>>  +		data.channel = dma_spec->args[1];
>>  +	} else if (dma_spec->args_count == 3) {
>>  +		data.transfer_type_tx = dma_spec->args[0];
>>  +		data.transfer_type_rx = dma_spec->args[1];
> 
> aha so you have a different values for tx and rx, that seems okay. 
> Maybe
> word a better in binding and also add examples in binding for this

Alright.

Cheers,
-Paul

> 
>>  +		data.channel = dma_spec->args[2];
>>  +	} else {
>>   		return NULL;
>>  -
>>  -	data.transfer_type = dma_spec->args[0];
>>  -	data.channel = dma_spec->args[1];
>>  +	}
>> 
>>   	if (data.channel > -1) {
>>   		if (data.channel >= jzdma->soc_data->nb_channels) {
>>  @@ -822,7 +837,8 @@ static struct dma_chan 
>> *jz4780_of_dma_xlate(struct of_phandle_args *dma_spec,
>>   			return NULL;
>>   		}
>> 
>>  -		jzdma->chan[data.channel].transfer_type = data.transfer_type;
>>  +		jzdma->chan[data.channel].transfer_type_tx = 
>> data.transfer_type_tx;
>>  +		jzdma->chan[data.channel].transfer_type_rx = 
>> data.transfer_type_rx;
>> 
>>   		return dma_get_slave_channel(
>>   			&jzdma->chan[data.channel].vchan.chan);
>>  --
>>  2.33.0
> 
> --
> ~Vinod