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


From: Philippe Mathieu-Daudé
Subject: Re: [PATCH v2 1/2] bcm2835_dma: Fix the ylen loop in TD mode
Date: Mon, 3 Feb 2020 17:27:56 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1

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 <address@hidden>
---
  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 <address@hidden>




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