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

Emil Renner Berthing
2023-10-03T07:35:37Z

shravan chippa wrote:
> From: Shravan Chippa <shravan.chippa@microchip.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@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 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