[PATCH 1/5] dmaengine: mxs-dma: add dma support for i.MX23/28

On Wed, Feb 09, 2011 at 09:34:00AM +0100, Sascha Hauer wrote:

Shawn,

On Wed, Feb 09, 2011 at 07:28:34AM +0800, Shawn Guo wrote:

quoted

quoted

quoted

+
+     if (direction == DMA_NONE) {
+             ccw = &mxs_chan->ccw[0];
+             pio = (u32 *) sgl;
+
+             for (j = 0; j < sg_len;)
+                     ccw->pio_words[j++] = *pio++;
+
+             ccw->next = 0;
+             ccw->bits.chain = 0;
+             ccw->bits.irq = 1;
+             ccw->bits.dec_sem = 1;
+             ccw->bits.wait4end = flags;
+             ccw->bits.halt_on_terminate = 1;
+             ccw->bits.terminate_flush = 1;
+             ccw->bits.pio_num = sg_len;
+             ccw->bits.command = MXS_DMA_NO_XFER;

Does this have a valid usecase? I would just return some error code
here. pio_num and pio_words are unused in the driver and I don't think
a dmaengine driver should have some kind of PIO fallback.

If you happen to have a look at mxs-mmc patch set, you could find it.

As Russell already pointed out, the (mmc-) driver should handle this.

quoted

quoted

quoted

+
+     /*
+      * dmaengine clients have to use dma_device.dev_id to filter
+      * dma device between apbh and apbx, so need to ensure it is
+      * identical to mxs_dma_engine.dev_id.
+      */
+     if (mxs_dma->dma_device.dev_id != mxs_dma->dev_id) {
+             dev_err(&pdev->dev, "dev_id of dma_device %d differs from mxs_dma_engine %d\n",
+                             mxs_dma->dma_device.dev_id, mxs_dma->dev_id);
+             goto err_init;
+     }

I think it makes more sense to match against device names (apbh vs.
apbx) in the client's filter function than to rely on exact numbering.

I agree, if there is already a member like dev_name in dma_device.
There is dev_id but no dev_name.  Suggestion on how to use device
name for matching?

Have a look at the implementation of imx_dma_is_general_purpose() and
imx_dma_is_ipu().

Great example.  Thanks.

Regards
Shawn