dmaengine: sh: rz-dmac: Save the start LM descriptor

Save the start LM descriptor to avoid starting from the beginning of the
channel's LM descriptor list in rz_dmac_calculate_residue_bytes_in_vd().
This avoids unnecessary iterations.

Tested-by: John Madieu <john.madieu.xa@bp.renesas.com>
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Tested-by: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
Link: https://patch.msgid.link/20260526084710.3491480-7-claudiu.beznea@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>

diff --git a/drivers/dma/sh/rz-dmac.c b/drivers/dma/sh/rz-dmac.c
index c48858b68dee631acda0fa517d4bf59b49ce56ba..d3926ecd63ac1041e21431e2eb9e44107523d047 100644 (file)
--- a/drivers/dma/sh/rz-dmac.c
+++ b/drivers/dma/sh/rz-dmac.c
@@ -58,6 +58,7 @@ struct rz_dmac_desc {
        /* For slave sg */
        struct scatterlist *sg;
        unsigned int sgcount;
+       struct rz_lmdesc *start_lmdesc;
 };
 
 #define to_rz_dmac_desc(d)     container_of(d, struct rz_dmac_desc, vd)
@@ -343,6 +344,8 @@ static void rz_dmac_prepare_desc_for_memcpy(struct rz_dmac_chan *channel)
        struct rz_dmac_desc *d = channel->desc;
        u32 chcfg = CHCFG_MEM_COPY;
 
+       d->start_lmdesc = lmdesc;
+
        /* prepare descriptor */
        lmdesc->sa = d->src;
        lmdesc->da = d->dest;
@@ -377,6 +380,7 @@ static void rz_dmac_prepare_descs_for_slave_sg(struct rz_dmac_chan *channel)
        }
 
        lmdesc = channel->lmdesc.tail;
+       d->start_lmdesc = lmdesc;
 
        for (i = 0, sg = sgl; i < sg_len; i++, sg = sg_next(sg)) {
                if (d->direction == DMA_DEV_TO_MEM) {
@@ -693,9 +697,10 @@ rz_dmac_get_next_lmdesc(struct rz_lmdesc *base, struct rz_lmdesc *lmdesc)
        return next;
 }
 
-static u32 rz_dmac_calculate_residue_bytes_in_vd(struct rz_dmac_chan *channel, u32 crla)
+static u32 rz_dmac_calculate_residue_bytes_in_vd(struct rz_dmac_chan *channel,
+                                                struct rz_dmac_desc *desc, u32 crla)
 {
-       struct rz_lmdesc *lmdesc = channel->lmdesc.head;
+       struct rz_lmdesc *lmdesc = desc->start_lmdesc;
        struct dma_chan *chan = &channel->vc.chan;
        struct rz_dmac *dmac = to_rz_dmac(chan->device);
        u32 residue = 0, i = 0;
@@ -794,7 +799,7 @@ static u32 rz_dmac_chan_get_residue(struct rz_dmac_chan *channel,
         * Calculate number of bytes transferred in processing virtual descriptor.
         * One virtual descriptor can have many lmdesc.
         */
-       return crtb + rz_dmac_calculate_residue_bytes_in_vd(channel, crla);
+       return crtb + rz_dmac_calculate_residue_bytes_in_vd(channel, current_desc, crla);
 }
 
 static enum dma_status rz_dmac_tx_status(struct dma_chan *chan,