Re: [PATCH v6 2/2] dma: Add Xilinx AXI Video Direct Memory Access Engine driver support

Srikanth Thokala
2014-03-24T16:35:33Z

On Mon, Mar 24, 2014 at 8:53 PM, Jassi Brar <jassisinghbrar@gmail.com> wrote:
> On Mon, Mar 24, 2014 at 8:44 PM, Srikanth Thokala <sthokal@xilinx.com> wrote:
>> On Mon, Mar 24, 2014 at 4:21 PM, Jassi Brar <jaswinder.singh@linaro.org> wrote:
>>> On 24 March 2014 14:30, Srikanth Thokala <sthokal@xilinx.com> wrote:
>>>> Hi Jassi,
>>>>
>>>> Thanks for the Acked-by.
>>>>
>>>> On Mon, Mar 24, 2014 at 11:50 AM, Jassi Brar <jassisinghbrar@gmail.com> wrote:
>>>>> On Tue, Mar 18, 2014 at 12:36 AM, Srikanth Thokala <sthokal@xilinx.com> wrote:
>>>>>
>>>>>> +
>>>>>> +/**
>>>>>> + * xilinx_vdma_prep_slave_sg - prepare a descriptor for a DMA_SLAVE transaction
>>>>>
>>>>> Should be xilinx_vdma_dma_prep_interleaved here.
>>>>
>>>> Ok, I will correct it. Thanks.
>>>>
>>>>>
>>>>>> +/**
>>>>>> + * xilinx_vdma_channel_set_config - Configure VDMA channel
>>>>>> + * Run-time configuration for Axi VDMA, supports:
>>>>>> + * . halt the channel
>>>>>> + * . configure interrupt coalescing and inter-packet delay threshold
>>>>>> + * . start/stop parking
>>>>>> + * . enable genlock
>>>>>> + *
>>>>>> + * @dchan: DMA channel
>>>>>> + * @cfg: VDMA device configuration pointer
>>>>>> + *
>>>>>> + * Return: '0' on success and failure value on error
>>>>>> + */
>>>>>> +int xilinx_vdma_channel_set_config(struct dma_chan *dchan,
>>>>>> + struct xilinx_vdma_config *cfg)
>>>>>> +{
>>>>>> + struct xilinx_vdma_chan *chan = to_xilinx_chan(dchan);
>>>>>> + u32 dmacr;
>>>>>> +
>>>>>> + if (cfg->reset)
>>>>>> + return xilinx_vdma_chan_reset(chan);
>>>>>> +
>>>>>> + dmacr = vdma_ctrl_read(chan, XILINX_VDMA_REG_DMACR);
>>>>>> +
>>>>>> + chan->config.frm_dly = cfg->frm_dly;
>>>>>> + chan->config.park = cfg->park;
>>>>>> +
>>>>>> + /* genlock settings */
>>>>>> + chan->config.gen_lock = cfg->gen_lock;
>>>>>> + chan->config.master = cfg->master;
>>>>>> +
>>>>>> + if (cfg->gen_lock && chan->genlock) {
>>>>>> + dmacr |= XILINX_VDMA_DMACR_GENLOCK_EN;
>>>>>> + dmacr |= cfg->master << XILINX_VDMA_DMACR_MASTER_SHIFT;
>>>>>> + }
>>>>>> +
>>>>>> + chan->config.frm_cnt_en = cfg->frm_cnt_en;
>>>>>> + if (cfg->park)
>>>>>> + chan->config.park_frm = cfg->park_frm;
>>>>>> + else
>>>>>> + chan->config.park_frm = -1;
>>>>>> +
>>>>>> + chan->config.coalesc = cfg->coalesc;
>>>>>> + chan->config.delay = cfg->delay;
>>>>>> +
>>>>>> + if (cfg->coalesc <= XILINX_VDMA_DMACR_FRAME_COUNT_MAX) {
>>>>>> + dmacr |= cfg->coalesc << XILINX_VDMA_DMACR_FRAME_COUNT_SHIFT;
>>>>>> + chan->config.coalesc = cfg->coalesc;
>>>>>> + }
>>>>>> +
>>>>>> + if (cfg->delay <= XILINX_VDMA_DMACR_DELAY_MAX) {
>>>>>> + dmacr |= cfg->delay << XILINX_VDMA_DMACR_DELAY_SHIFT;
>>>>>> + chan->config.delay = cfg->delay;
>>>>>> + }
>>>>>> +
>>>>>> + /* FSync Source selection */
>>>>>> + dmacr &= ~XILINX_VDMA_DMACR_FSYNCSRC_MASK;
>>>>>> + dmacr |= cfg->ext_fsync << XILINX_VDMA_DMACR_FSYNCSRC_SHIFT;
>>>>>> +
>>>>>> + vdma_ctrl_write(chan, XILINX_VDMA_REG_DMACR, dmacr);
>>>>>> +
>>>>>> + return 0;
>>>>>> +}
>>>>>> +EXPORT_SYMBOL(xilinx_vdma_channel_set_config);
>>>>>> +
>>>>> Bypassing the DMAEngine api doesn't seem very neat.
>>>>> Is there currently any client driver that /changes/ this configuration
>>>>> between channel requests? If no, then simply get the configuration
>>>>> from DT node and avoid this api.
>>>>
>>>> This change is recently suggested by Lars in the following patch series,
>>>> "dma: Remove comment about embedding dma_slave_config into custom structs"
>>>>
>>> If some user does indeed need to /change/ the configuration across
>>> channel requests, we can keep function. Is there currently any such
>>> user?
>>
>> Yes, we are planning to push these changes soon to drivers/media/.
>>
> This is not what I asked though. I asked if some client driver changes
> the configuration options based on some runtime decision? If yes, then
> the api is warranted. Otherwise, you might consider getting the static
> configuration from DT. That's all I suggest.

Yes, the client driver can change the configuration in the runtime
like the park_frm
option, for example, decides on which frame to park on.

Srikanth

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