From: Frank Chang <frank.chang@sifive.com>

Real PDMA doesn't set Control.error if there are 0 bytes to be
transferred. The DMA transfer is still success.

The following result is PDMA tested in U-boot on Unmatched board:

=> mw.l 0x3000000 0x0                      <= Disclaim channel 0
=> mw.l 0x3000000 0x1                      <= Claim channel 0
=> mw.l 0x3000004 0x55000000               <= wsize = rsize = 5 (2^5 = 32 bytes)
=> mw.q 0x3000008 0x0                      <= NextBytes = 0
=> mw.q 0x3000010 0x84000000               <= NextDestination = 0x84000000
=> mw.q 0x3000018 0x84001000               <= NextSource = 0x84001000
=> mw.l 0x84000000 0x87654321              <= Fill test data to dst
=> mw.l 0x84001000 0x12345678              <= Fill test data to src
=> md.l 0x84000000 1; md.l 0x84001000 1    <= Dump src/dst memory contents
84000000: 87654321                               !Ce.
84001000: 12345678                               xV4.
=> md.l 0x3000000 8                        <= Dump PDMA status
03000000: 00000001 55000000 00000000 00000000    .......U........
03000010: 84000000 00000000 84001000 00000000    ................
=> mw.l 0x3000000 0x3                      <= Set channel 0 run and claim bits
=> md.l 0x3000000 8                        <= Dump PDMA status
03000000: 40000001 55000000 00000000 00000000    ...@...U........
03000010: 84000000 00000000 84001000 00000000    ................
=> md.l 0x84000000 1; md.l 0x84001000 1    <= Dump src/dst memory contents
84000000: 87654321                               !Ce.
84001000: 12345678                               xV4.

Signed-off-by: Frank Chang <frank.chang@sifive.com>
Tested-by: Max Hsu <max.hsu@sifive.com>
---
 hw/dma/sifive_pdma.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/hw/dma/sifive_pdma.c b/hw/dma/sifive_pdma.c
index d6980fbbd62..133db817dc7 100644
--- a/hw/dma/sifive_pdma.c
+++ b/hw/dma/sifive_pdma.c
@@ -76,7 +76,7 @@ static void sifive_pdma_run(SiFivePDMAState *s, int ch)
 
     /* do nothing if bytes to transfer is zero */
     if (!bytes) {
-        goto error;
+        goto done;
     }
 
     /*
@@ -131,11 +131,6 @@ static void sifive_pdma_run(SiFivePDMAState *s, int ch)
         s->chan[ch].exec_bytes -= remainder;
     }
 
-    /* indicate a DMA transfer is done */
-    s->chan[ch].state = DMA_CHAN_STATE_DONE;
-    s->chan[ch].control &= ~CONTROL_RUN;
-    s->chan[ch].control |= CONTROL_DONE;
-
     /* reload exec_ registers if repeat is required */
     if (s->chan[ch].next_config & CONFIG_REPEAT) {
         s->chan[ch].exec_bytes = bytes;
@@ -143,6 +138,11 @@ static void sifive_pdma_run(SiFivePDMAState *s, int ch)
         s->chan[ch].exec_src = src;
     }
 
+done:
+    /* indicate a DMA transfer is done */
+    s->chan[ch].state = DMA_CHAN_STATE_DONE;
+    s->chan[ch].control &= ~CONTROL_RUN;
+    s->chan[ch].control |= CONTROL_DONE;
     return;
 
 error:
-- 
2.25.1

On Fri, Sep 10, 2021 at 1:59 PM <frank.chang@sifive.com> wrote:
>
> From: Frank Chang <frank.chang@sifive.com>
>
> Real PDMA doesn't set Control.error if there are 0 bytes to be

nits: 0 byte
Please fix the commit title as well

> transferred. The DMA transfer is still success.
>
> The following result is PDMA tested in U-boot on Unmatched board:

%s/U-boot/U-Boot

>
> => mw.l 0x3000000 0x0                      <= Disclaim channel 0
> => mw.l 0x3000000 0x1                      <= Claim channel 0
> => mw.l 0x3000004 0x55000000               <= wsize = rsize = 5 (2^5 = 32 bytes)
> => mw.q 0x3000008 0x0                      <= NextBytes = 0
> => mw.q 0x3000010 0x84000000               <= NextDestination = 0x84000000
> => mw.q 0x3000018 0x84001000               <= NextSource = 0x84001000
> => mw.l 0x84000000 0x87654321              <= Fill test data to dst
> => mw.l 0x84001000 0x12345678              <= Fill test data to src
> => md.l 0x84000000 1; md.l 0x84001000 1    <= Dump src/dst memory contents
> 84000000: 87654321                               !Ce.
> 84001000: 12345678                               xV4.
> => md.l 0x3000000 8                        <= Dump PDMA status
> 03000000: 00000001 55000000 00000000 00000000    .......U........
> 03000010: 84000000 00000000 84001000 00000000    ................
> => mw.l 0x3000000 0x3                      <= Set channel 0 run and claim bits
> => md.l 0x3000000 8                        <= Dump PDMA status
> 03000000: 40000001 55000000 00000000 00000000    ...@...U........
> 03000010: 84000000 00000000 84001000 00000000    ................
> => md.l 0x84000000 1; md.l 0x84001000 1    <= Dump src/dst memory contents
> 84000000: 87654321                               !Ce.
> 84001000: 12345678                               xV4.
>
> Signed-off-by: Frank Chang <frank.chang@sifive.com>
> Tested-by: Max Hsu <max.hsu@sifive.com>
> ---
>  hw/dma/sifive_pdma.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
>

Otherwise,
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>