Re: [PATCH v1 3/3] dmaengine: sf-pdma: add mpfs-pdma compatible name

[Conor Dooley <conor@kernel.org>]

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Hey Shravan,

On Fri, Sep 22, 2023 at 03:20:39PM +0530, shravan chippa wrote:
> From: Shravan Chippa <shravan.chippa@microchip.com>
> 
> Sifive platform dma does not allow out-of-order transfers,

Can you remind me why we determined that this was the case?
IOW, why could we not enable the out-of-order transfers and get a
performance benefit for everyone? It's been a year or so (I think) and I
have forgotten.

Cheers,
Conor.

> buf out-of-order dma has a significant performance advantage.
> Add a PolarFire SoC specific compatible and code to support
> for out-of-order dma transfers
> 
> Signed-off-by: Shravan Chippa <shravan.chippa@microchip.com>
> Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> ---
>  drivers/dma/sf-pdma/sf-pdma.c | 27 ++++++++++++++++++++++++---
>  drivers/dma/sf-pdma/sf-pdma.h |  6 ++++++
>  2 files changed, 30 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/dma/sf-pdma/sf-pdma.c b/drivers/dma/sf-pdma/sf-pdma.c
> index c7558c9f9ac3..992a804166d5 100644
> --- a/drivers/dma/sf-pdma/sf-pdma.c
> +++ b/drivers/dma/sf-pdma/sf-pdma.c
> @@ -21,6 +21,7 @@
>  #include <linux/dma-mapping.h>
>  #include <linux/of.h>
>  #include <linux/of_dma.h>
> +#include <linux/of_device.h>
>  #include <linux/slab.h>
>  
>  #include "sf-pdma.h"
> @@ -66,7 +67,7 @@ static struct sf_pdma_desc *sf_pdma_alloc_desc(struct sf_pdma_chan *chan)
>  static void sf_pdma_fill_desc(struct sf_pdma_desc *desc,
>  			      u64 dst, u64 src, u64 size)
>  {
> -	desc->xfer_type = PDMA_FULL_SPEED;
> +	desc->xfer_type =  desc->chan->pdma->transfer_type;
>  	desc->xfer_size = size;
>  	desc->dst_addr = dst;
>  	desc->src_addr = src;
> @@ -520,6 +521,7 @@ static struct dma_chan *sf_pdma_of_xlate(struct of_phandle_args *dma_spec,
>  
>  static int sf_pdma_probe(struct platform_device *pdev)
>  {
> +	const struct sf_pdma_driver_platdata *ddata;
>  	struct sf_pdma *pdma;
>  	int ret, n_chans;
>  	const enum dma_slave_buswidth widths =
> @@ -545,6 +547,14 @@ static int sf_pdma_probe(struct platform_device *pdev)
>  
>  	pdma->n_chans = n_chans;
>  
> +	pdma->transfer_type = PDMA_FULL_SPEED;
> +
> +	ddata  = of_device_get_match_data(&pdev->dev);
> +	if (ddata) {
> +		if (ddata->quirks & NO_STRICT_ORDERING)
> +			pdma->transfer_type &= ~(NO_STRICT_ORDERING);
> +	}
> +
>  	pdma->membase = devm_platform_ioremap_resource(pdev, 0);
>  	if (IS_ERR(pdma->membase))
>  		return PTR_ERR(pdma->membase);
> @@ -629,11 +639,22 @@ static int sf_pdma_remove(struct platform_device *pdev)
>  	return 0;
>  }
>  
> +static const struct sf_pdma_driver_platdata mpfs_pdma = {
> +	.quirks = NO_STRICT_ORDERING,
> +};
> +
>  static const struct of_device_id sf_pdma_dt_ids[] = {
> -	{ .compatible = "sifive,fu540-c000-pdma" },
> -	{ .compatible = "sifive,pdma0" },
> +	{
> +		.compatible = "sifive,fu540-c000-pdma",
> +	}, {
> +		.compatible = "sifive,pdma0",
> +	}, {
> +		.compatible = "microchip,mpfs-pdma",
> +		.data	    = &mpfs_pdma,
> +	},
>  	{},
>  };
> +
>  MODULE_DEVICE_TABLE(of, sf_pdma_dt_ids);
>  
>  static struct platform_driver sf_pdma_driver = {
> diff --git a/drivers/dma/sf-pdma/sf-pdma.h b/drivers/dma/sf-pdma/sf-pdma.h
> index 5c398a83b491..3b16db4daa0b 100644
> --- a/drivers/dma/sf-pdma/sf-pdma.h
> +++ b/drivers/dma/sf-pdma/sf-pdma.h
> @@ -49,6 +49,7 @@
>  
>  /* Transfer Type */
>  #define PDMA_FULL_SPEED					0xFF000008
> +#define NO_STRICT_ORDERING				BIT(3)
>  
>  /* Error Recovery */
>  #define MAX_RETRY					1
> @@ -112,8 +113,13 @@ struct sf_pdma {
>  	struct dma_device       dma_dev;
>  	void __iomem            *membase;
>  	void __iomem            *mappedbase;
> +	u32			transfer_type;
>  	u32			n_chans;
>  	struct sf_pdma_chan	chans[];
>  };
>  
> +struct sf_pdma_driver_platdata {
> +	u32 quirks;
> +};
> +
>  #endif /* _SF_PDMA_H */
> -- 
> 2.34.1
> 

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