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    SubjectRe: [PATCH] dma: imx-sdma: Add FIFO offset support for multi FIFO script
    On Thu, Jun 02, 2022 at 05:53:47PM +0800, Shengjiu Wang wrote:
    > The peripheral may have several FIFOs, but some case just select
    > some FIFOs from them for data transfer, which means FIFO0 and FIFO2
    > may be selected. So add FIFO address offset support, 0 means all FIFOs
    > are continuous, 1 means 1 word offset between FIFOs. All offset between
    > FIFOs should be same.
    >
    > Another option words_per_fifo means how many audio channel data copied
    > to one FIFO one time, 0 means one channel per FIFO, 1 means 2 channels
    > per FIFO.
    >
    > If 'n_fifos_src = 4' and 'words_per_fifo = 1', it means the first two
    > words(channels) fetch from FIFO0 and then jump to FIFO1 for next two words,
    > and so on after the last FIFO3 fetched, roll back to FIFO0.
    >
    > Signed-off-by: Joy Zou <joy.zou@nxp.com>
    > Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
    > ---
    > drivers/dma/imx-sdma.c | 26 ++++++++++++++++++++++++--
    > include/linux/dma/imx-dma.h | 13 +++++++++++++
    > 2 files changed, 37 insertions(+), 2 deletions(-)
    >
    > diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
    > index 111beb7138e0..3c95719286bc 100644
    > --- a/drivers/dma/imx-sdma.c
    > +++ b/drivers/dma/imx-sdma.c
    > @@ -183,6 +183,8 @@
    > BIT(DMA_DEV_TO_DEV))
    >
    > #define SDMA_WATERMARK_LEVEL_N_FIFOS GENMASK(15, 12)
    > +#define SDMA_WATERMARK_LEVEL_OFF_FIFOS GENMASK(19, 16)
    > +#define SDMA_WATERMARK_LEVEL_WORDS_PER_FIFO GENMASK(31, 28)
    > #define SDMA_WATERMARK_LEVEL_SW_DONE BIT(23)
    >
    > #define SDMA_DONE0_CONFIG_DONE_SEL BIT(7)
    > @@ -429,6 +431,9 @@ struct sdma_desc {
    > * @n_fifos_src: number of source device fifos
    > * @n_fifos_dst: number of destination device fifos
    > * @sw_done: software done flag
    > + * @off_fifos_src: offset for source device FIFOs
    > + * @off_fifos_dst: offset for destination device FIFOs
    > + * @words_per_fifo: copy number of words one time for one FIFO
    > */
    > struct sdma_channel {
    > struct virt_dma_chan vc;
    > @@ -456,6 +461,9 @@ struct sdma_channel {
    > bool is_ram_script;
    > unsigned int n_fifos_src;
    > unsigned int n_fifos_dst;
    > + unsigned int off_fifos_src;
    > + unsigned int off_fifos_dst;
    > + unsigned int words_per_fifo;
    > bool sw_done;
    > };
    >
    > @@ -1245,17 +1253,28 @@ static void sdma_set_watermarklevel_for_p2p(struct sdma_channel *sdmac)
    > static void sdma_set_watermarklevel_for_sais(struct sdma_channel *sdmac)
    > {
    > unsigned int n_fifos;
    > + unsigned int off_fifos;
    > + unsigned int words_per_fifo;
    >
    > if (sdmac->sw_done)
    > sdmac->watermark_level |= SDMA_WATERMARK_LEVEL_SW_DONE;
    >
    > - if (sdmac->direction == DMA_DEV_TO_MEM)
    > + if (sdmac->direction == DMA_DEV_TO_MEM) {
    > n_fifos = sdmac->n_fifos_src;
    > - else
    > + off_fifos = sdmac->off_fifos_src;
    > + } else {
    > n_fifos = sdmac->n_fifos_dst;
    > + off_fifos = sdmac->off_fifos_dst;
    > + }
    > +
    > + words_per_fifo = sdmac->words_per_fifo;
    >
    > sdmac->watermark_level |=
    > FIELD_PREP(SDMA_WATERMARK_LEVEL_N_FIFOS, n_fifos);
    > + sdmac->watermark_level |=
    > + FIELD_PREP(SDMA_WATERMARK_LEVEL_OFF_FIFOS, off_fifos);
    > + sdmac->watermark_level |=
    > + FIELD_PREP(SDMA_WATERMARK_LEVEL_WORDS_PER_FIFO, (words_per_fifo - 1));
    > }
    >
    > static int sdma_config_channel(struct dma_chan *chan)
    > @@ -1769,6 +1788,9 @@ static int sdma_config(struct dma_chan *chan,
    > }
    > sdmac->n_fifos_src = sdmacfg->n_fifos_src;
    > sdmac->n_fifos_dst = sdmacfg->n_fifos_dst;
    > + sdmac->off_fifos_src = sdmacfg->off_fifos_src;
    > + sdmac->off_fifos_dst = sdmacfg->off_fifos_dst;
    > + sdmac->words_per_fifo = sdmacfg->words_per_fifo;
    > sdmac->sw_done = sdmacfg->sw_done;
    > }
    >
    > diff --git a/include/linux/dma/imx-dma.h b/include/linux/dma/imx-dma.h
    > index 8887762360d4..0c739d571956 100644
    > --- a/include/linux/dma/imx-dma.h
    > +++ b/include/linux/dma/imx-dma.h
    > @@ -70,6 +70,16 @@ static inline int imx_dma_is_general_purpose(struct dma_chan *chan)
    > * struct sdma_peripheral_config - SDMA config for audio
    > * @n_fifos_src: Number of FIFOs for recording
    > * @n_fifos_dst: Number of FIFOs for playback
    > + * @off_fifos_src: FIFO address offset for recording, 0 means all FIFOs are
    > + * continuous, 1 means 1 word offset between FIFOs. All offset
    > + * between FIFOs should be same.
    > + * @off_fifos_dst: FIFO address offset for playback

    I think 'stride' better describes what you mean here and is more
    commonly used for the distance between registers.

    > + * @words_per_fifo: numbers of words per FIFO fetch/fill, 0 means
    > + * one channel per FIFO, 1 means 2 channels per FIFO..
    > + * If 'n_fifos_src = 4' and 'words_per_fifo = 1', it
    > + * means the first two words(channels) fetch from FIFO0
    > + * and then jump to FIFO1 for next two words, and so on
    > + * after the last FIFO3 fetched, roll back to FIFO0.

    The description seems wrong. words_per_fifo is used like this above:

    sdmac->watermark_level |=
    FIELD_PREP(SDMA_WATERMARK_LEVEL_WORDS_PER_FIFO, (words_per_fifo - 1));

    A value of 0 for words_per_fifo doesn't look sane.

    Generally it would be nice to see this patch together with patches that
    use these new features.

    Sascha

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