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

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Date:	Mon, 24 Mar 2014 16:21:19 +0530
From:	Jassi Brar <jaswinder.singh@...aro.org>
To:	Srikanth Thokala <sthokal@...inx.com>
Cc:	Jassi Brar <jassisinghbrar@...il.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Vinod Koul <vinod.koul@...el.com>,
	Michal Simek <michal.simek@...inx.com>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Levente Kurusa <levex@...ux.com>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	dmaengine@...r.kernel.org,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v6 2/2] dma: Add Xilinx AXI Video Direct Memory Access
 Engine driver support

On 24 March 2014 14:30, Srikanth Thokala <sthokal@...inx.com> wrote:
> Hi Jassi,
>
> Thanks for the Acked-by.
>
> On Mon, Mar 24, 2014 at 11:50 AM, Jassi Brar <jassisinghbrar@...il.com> wrote:
>> On Tue, Mar 18, 2014 at 12:36 AM, Srikanth Thokala <sthokal@...inx.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?
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