[PATCH v2 1/2] bcm2835_dma: Fix the ylen loop in TD mode

[PATCH v2 1/2] bcm2835_dma: Fix the ylen loop in TD mode

[Rene Stange]

In TD (two dimensions) DMA mode ylen has to be increased by one after
reading it from the TXFR_LEN register, because a value of zero has to
result in one run through of the ylen loop. This has been tested on a
real Raspberry Pi 3 Model B+. In the previous implementation the ylen
loop was not passed at all for a value of zero.

Signed-off-by: Rene Stange <rsta2@o2online.de>
---
 hw/dma/bcm2835_dma.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/hw/dma/bcm2835_dma.c b/hw/dma/bcm2835_dma.c
index 1e458d7fba..667d951a6f 100644
--- a/hw/dma/bcm2835_dma.c
+++ b/hw/dma/bcm2835_dma.c
@@ -70,14 +70,14 @@ static void bcm2835_dma_update(BCM2835DMAState *s, unsigned c)
         ch->stride = ldl_le_phys(&s->dma_as, ch->conblk_ad + 16);
         ch->nextconbk = ldl_le_phys(&s->dma_as, ch->conblk_ad + 20);
 
+        ylen = 1;
         if (ch->ti & BCM2708_DMA_TDMODE) {
             /* 2D transfer mode */
-            ylen = (ch->txfr_len >> 16) & 0x3fff;
+            ylen += (ch->txfr_len >> 16) & 0x3fff;
             xlen = ch->txfr_len & 0xffff;
             dst_stride = ch->stride >> 16;
             src_stride = ch->stride & 0xffff;
         } else {
-            ylen = 1;
             xlen = ch->txfr_len;
             dst_stride = 0;
             src_stride = 0;
-- 
2.16.4

Re: [PATCH v2 1/2] bcm2835_dma: Fix the ylen loop in TD mode

[Philippe Mathieu-Daudé]

On 2/3/20 4:40 PM, Rene Stange wrote:
> In TD (two dimensions) DMA mode ylen has to be increased by one after
> reading it from the TXFR_LEN register, because a value of zero has to
> result in one run through of the ylen loop. This has been tested on a
> real Raspberry Pi 3 Model B+. In the previous implementation the ylen
> loop was not passed at all for a value of zero.
> 
> Signed-off-by: Rene Stange <rsta2@o2online.de>
> ---
>   hw/dma/bcm2835_dma.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/dma/bcm2835_dma.c b/hw/dma/bcm2835_dma.c
> index 1e458d7fba..667d951a6f 100644
> --- a/hw/dma/bcm2835_dma.c
> +++ b/hw/dma/bcm2835_dma.c
> @@ -70,14 +70,14 @@ static void bcm2835_dma_update(BCM2835DMAState *s, unsigned c)
>           ch->stride = ldl_le_phys(&s->dma_as, ch->conblk_ad + 16);
>           ch->nextconbk = ldl_le_phys(&s->dma_as, ch->conblk_ad + 20);
>   
> +        ylen = 1;
>           if (ch->ti & BCM2708_DMA_TDMODE) {
>               /* 2D transfer mode */
> -            ylen = (ch->txfr_len >> 16) & 0x3fff;
> +            ylen += (ch->txfr_len >> 16) & 0x3fff;
>               xlen = ch->txfr_len & 0xffff;
>               dst_stride = ch->stride >> 16;
>               src_stride = ch->stride & 0xffff;
>           } else {
> -            ylen = 1;
>               xlen = ch->txfr_len;
>               dst_stride = 0;
>               src_stride = 0;
> 

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>