linux-kernel - Re: [PATCH v2 3/4] dmaengine: sf-pdma: add mpfs-pdma compatible name

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Message-ID: <CAJM55Z8+UtVwFRxOKPcNKmitzkZQ9tyecG46dhTZqiYZgw903Q@mail.gmail.com>
Date:   Tue, 3 Oct 2023 00:35:10 -0700
From:   Emil Renner Berthing <emil.renner.berthing@...onical.com>
To:     shravan chippa <shravan.chippa@...rochip.com>,
        green.wan@...ive.com, vkoul@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, palmer@...belt.com,
        paul.walmsley@...ive.com, conor+dt@...nel.org
Cc:     dmaengine@...r.kernel.org, devicetree@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        nagasuresh.relli@...rochip.com, praveen.kumar@...rochip.com
Subject: Re: [PATCH v2 3/4] dmaengine: sf-pdma: add mpfs-pdma compatible name

shravan chippa wrote:
> From: Shravan Chippa <shravan.chippa@...rochip.com>
>
> Sifive platform dma does not allow out-of-order transfers,
> Add a PolarFire SoC specific compatible and code to support
> for out-of-order dma transfers
>
> Signed-off-by: Shravan Chippa <shravan.chippa@...rochip.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 06a0912a12a1..a9ff319d4ca3 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;

Two spaces.

>  	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);
> +	}
> +

The commit message says "Sifive platform dma does not allow out-of-order
transfers" so you want strict ordering by default and then allow
out-of-order transfers if the match data allows it, right?

But here bit 3 is set by default and cleared if the quirk is set, so it looks
like bit 3 actually means "strict ordering" and not "no strict ordering" as
you've named it.

The confusion here probably stems using the same define for the quirk and the
xfer_type. Unless I'm mistaken above I'd find something like this a lot easier
to read:

sf_pdma.h:
#define PDMA_FULL_SPEED		0xFF000000
#define PDMA_STRICT_ORDERING	BIT(3)

sf_pdma.c:
#define PDMA_QUIRK_NO_STRICT_ORDERING	BIT(0)

dma->transfer_type = PDMA_FULL_SPEED | PDMA_STRICT_ORDERING;
...
if (ddata->quirks & PDMA_QUIRK_NO_STRICT_ORDERING)
	pdma->transfer_type &= ~PDMA_STRICT_ORDERING;

>  	pdma->membase = devm_platform_ioremap_resource(pdev, 0);
>  	if (IS_ERR(pdma->membase))
>  		return PTR_ERR(pdma->membase);
> @@ -632,11 +642,22 @@ 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