Re: [PATCH v2 1/2] dmaengine: add Qualcomm BAM dma driver

[Arnd Bergmann <arnd@arndb.de>]

On Friday 10 January 2014, Andy Gross wrote:

> +static bool bam_dma_filter(struct dma_chan *chan, void *data)
> +{
> +	struct bam_filter_args *args = data;
> +	struct bam_chan *bchan = to_bam_chan(chan);
> +
> +	if (args->dev == chan->device &&
> +		args->id == bchan->id) {
> +
> +		/* we found the channel, so lets set the EE and dir */
> +		bchan->ee = args->ee;
> +		bchan->slave.direction = args->dir ?
> +				DMA_DEV_TO_MEM : DMA_MEM_TO_DEV;
> +		return true;
> +	}
> +
> +	return false;
> +}

A filter function should no longer be needed.

> +static struct dma_chan *bam_dma_xlate(struct of_phandle_args *dma_spec,
> +		struct of_dma *of)
> +{
> +	struct bam_filter_args args;
> +	dma_cap_mask_t cap;
> +
> +	if (dma_spec->args_count != 3)
> +		return NULL;
> +
> +	args.dev = of->of_dma_data;
> +	args.id = dma_spec->args[0];
> +	args.ee = dma_spec->args[1];
> +	args.dir = dma_spec->args[2];
> +
> +	dma_cap_zero(cap);
> +	dma_cap_set(DMA_SLAVE, cap);
> +
> +	return dma_request_channel(cap, bam_dma_filter, &args);
> +}

Instead, call dma_get_slave_channel() with the right channel that you already know
here.

> +	if (pdev->dev.of_node) {
> +		ret = of_dma_controller_register(pdev->dev.of_node,
> +				bam_dma_xlate, &bdev->common);
> +
> +		if (ret) {
> +			dev_err(bdev->dev, "failed to register of_dma\n");
> +			goto err_unregister_dma;
> +		}
> +	}

No need to check for pdev->dev.of_node when that is the only mode of probing.

> +
> +#ifdef CONFIG_OF
> +static const struct of_device_id bam_of_match[] = {
> +	{ .compatible = "qcom,bam-v1.4.0", },
> +	{ .compatible = "qcom,bam-v1.4.1", },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, bam_of_match);
> +#endif

Also, you can remove the #ifdef here and the of_match_ptr() below.

> +
> +static struct platform_driver bam_dma_driver = {
> +	.probe = bam_dma_probe,
> +	.remove = bam_dma_remove,
> +	.driver = {
> +		.name = "bam-dma-engine",
> +		.owner = THIS_MODULE,
> +		.of_match_table = of_match_ptr(bam_of_match),
> +	},
> +};
> +
> +static int __init bam_dma_init(void)
> +{
> +	return platform_driver_register(&bam_dma_driver);
> +}
> +
> +static void __exit bam_dma_exit(void)
> +{
> +	return platform_driver_unregister(&bam_dma_driver);
> +}
> +

module_platform_driver()

> diff --git a/drivers/dma/qcom_bam_dma.h b/drivers/dma/qcom_bam_dma.h
> new file mode 100644
> index 0000000..2cb3b5f
> --- /dev/null
> +++ b/drivers/dma/qcom_bam_dma.h
> @@ -0,0 +1,268 @@
> +#ifndef __QCOM_BAM_DMA_H__
> +#define __QCOM_BAM_DMA_H__
> +
> +#include <linux/dmaengine.h>
> +#include "virt-dma.h"
> +
> +enum bam_channel_dir {
> +	BAM_PIPE_CONSUMER = 0,	/* channel reads from data-fifo or memory */
> +	BAM_PIPE_PRODUCER,	/* channel writes to data-fifo or memory */
> +};

Since the header does not serve as an interface, just move all the contents
into the driver directly.

> +struct bam_desc_hw {
> +	u32 addr;		/* Buffer physical address */
> +	u16 size;		/* Buffer size in bytes */
> +	u16 flags;
> +} __packed;

Remove __packed here, it only makes the access less efficient but does not change
the layout, which is already packed.

	Arnd