[Qemu-devel] [PATCH] hw/dma: Fix dead code in pl080.c

[Qemu-devel] [PATCH] hw/dma: Fix dead code in pl080.c

[Sergio Andrés Gómez Del Real]

The patch fixes dead code in pl080_read() and pl080_write() as reported
in bug #1637974. According to ARM's official Technical Reference Manual,
offsets handled by the switch statement are 0x100, 0x104, 0x108, 0x10C
and 0x110, so the solution suggested by the guy who reported the bug is
right.

Signed-off-by: Sergio Andrés Gómez Del Real <Sergio.G.DelReal@gmail.com>
---
 hw/dma/pl080.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/hw/dma/pl080.c b/hw/dma/pl080.c
index 7724c93..8f34f24 100644
--- a/hw/dma/pl080.c
+++ b/hw/dma/pl080.c
@@ -255,7 +255,7 @@ static uint64_t pl080_read(void *opaque, hwaddr offset,
         i = (offset & 0xe0) >> 5;
         if (i >= s->nchannels)
             goto bad_offset;
-        switch (offset >> 2) {
+        switch ((offset-0x100) >> 2) {
         case 0: /* SrcAddr */
             return s->chan[i].src;
         case 1: /* DestAddr */
@@ -316,7 +316,7 @@ static void pl080_write(void *opaque, hwaddr offset,
         i = (offset & 0xe0) >> 5;
         if (i >= s->nchannels)
             goto bad_offset;
-        switch (offset >> 2) {
+        switch ((offset-0x100) >> 2) {
         case 0: /* SrcAddr */
             s->chan[i].src = value;
             break;
-- 
2.10.2

Re: [Qemu-devel] [PATCH] hw/dma: Fix dead code in pl080.c

[no-reply]

Hi,

Your series seems to have some coding style problems. See output below for
more information:

Message-id: 20161227165947.20184-1-Sergio.G.DelReal@gmail.com
Type: series
Subject: [Qemu-devel] [PATCH] hw/dma: Fix dead code in pl080.c

=== TEST SCRIPT BEGIN ===
#!/bin/bash

BASE=base
n=1
total=$(git log --oneline $BASE.. | wc -l)
failed=0

# Useful git options
git config --local diff.renamelimit 0
git config --local diff.renames True

commits="$(git log --format=%H --reverse $BASE..)"
for c in $commits; do
    echo "Checking PATCH $n/$total: $(git log -n 1 --format=%s $c)..."
    if ! git show $c --format=email | ./scripts/checkpatch.pl --mailback -; then
        failed=1
        echo
    fi
    n=$((n+1))
done

exit $failed
=== TEST SCRIPT END ===

Updating 3c8cf5a9c21ff8782164d1def7f44bd888713384
From https://github.com/patchew-project/qemu
 * [new tag]         patchew/20161227165947.20184-1-Sergio.G.DelReal@gmail.com -> patchew/20161227165947.20184-1-Sergio.G.DelReal@gmail.com
Switched to a new branch 'test'
682cfa2 hw/dma: Fix dead code in pl080.c

=== OUTPUT BEGIN ===
Checking PATCH 1/1: hw/dma: Fix dead code in pl080.c...
ERROR: spaces required around that '-' (ctx:VxV)
#28: FILE: hw/dma/pl080.c:258:
+        switch ((offset-0x100) >> 2) {
                        ^

ERROR: spaces required around that '-' (ctx:VxV)
#37: FILE: hw/dma/pl080.c:319:
+        switch ((offset-0x100) >> 2) {
                        ^

total: 2 errors, 0 warnings, 16 lines checked

Your patch has style problems, please review.  If any of these errors
are false positives report them to the maintainer, see
CHECKPATCH in MAINTAINERS.

=== OUTPUT END ===

Test command exited with code: 1


---
Email generated automatically by Patchew [http://patchew.org/].
Please send your feedback to patchew-devel@freelists.org

[Qemu-devel] [PATCH] hw/dma: Fix dead code in pl080.c

[Sergio Andrés Gómez Del Real]

The patch fixes dead code in pl080_read() and pl080_write() as reported
in bug #1637974. According to ARM's official Technical Reference Manual,
offsets handled by the switch statement are 0x100, 0x104, 0x108, 0x10C
and 0x110, so the solution suggested by the guy who reported the bug is
right.

Signed-off-by: Sergio Andrés Gómez Del Real <Sergio.G.DelReal@gmail.com>
---
 hw/dma/pl080.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/hw/dma/pl080.c b/hw/dma/pl080.c
index 7724c93..3b0c20b 100644
--- a/hw/dma/pl080.c
+++ b/hw/dma/pl080.c
@@ -255,7 +255,7 @@ static uint64_t pl080_read(void *opaque, hwaddr offset,
         i = (offset & 0xe0) >> 5;
         if (i >= s->nchannels)
             goto bad_offset;
-        switch (offset >> 2) {
+        switch ((offset - 0x100) >> 2) {
         case 0: /* SrcAddr */
             return s->chan[i].src;
         case 1: /* DestAddr */
@@ -316,7 +316,7 @@ static void pl080_write(void *opaque, hwaddr offset,
         i = (offset & 0xe0) >> 5;
         if (i >= s->nchannels)
             goto bad_offset;
-        switch (offset >> 2) {
+        switch ((offset - 0x100) >> 2) {
         case 0: /* SrcAddr */
             s->chan[i].src = value;
             break;
-- 
2.10.2

Re: [Qemu-devel] [PATCH] hw/dma: Fix dead code in pl080.c

[Peter Maydell]

On 27 December 2016 at 23:11, Sergio Andrés Gómez Del Real
<sergio.g.delreal@gmail.com> wrote:
> The patch fixes dead code in pl080_read() and pl080_write() as reported
> in bug #1637974. According to ARM's official Technical Reference Manual,
> offsets handled by the switch statement are 0x100, 0x104, 0x108, 0x10C
> and 0x110, so the solution suggested by the guy who reported the bug is
> right.
>
> Signed-off-by: Sergio Andrés Gómez Del Real <Sergio.G.DelReal@gmail.com>
> ---
>  hw/dma/pl080.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/hw/dma/pl080.c b/hw/dma/pl080.c
> index 7724c93..3b0c20b 100644
> --- a/hw/dma/pl080.c
> +++ b/hw/dma/pl080.c
> @@ -255,7 +255,7 @@ static uint64_t pl080_read(void *opaque, hwaddr offset,
>          i = (offset & 0xe0) >> 5;
>          if (i >= s->nchannels)
>              goto bad_offset;
> -        switch (offset >> 2) {
> +        switch ((offset - 0x100) >> 2) {
>          case 0: /* SrcAddr */
>              return s->chan[i].src;
>          case 1: /* DestAddr */
> @@ -316,7 +316,7 @@ static void pl080_write(void *opaque, hwaddr offset,
>          i = (offset & 0xe0) >> 5;
>          if (i >= s->nchannels)
>              goto bad_offset;
> -        switch (offset >> 2) {
> +        switch ((offset - 0x100) >> 2) {
>          case 0: /* SrcAddr */
>              s->chan[i].src = value;
>              break;
> --
> 2.10.2

Looking at the TRM, I don't think this fix is correct. The switches
are intended to handle all of the DMACC* DMA channel registers:

0x100 DMACC0SrcAddr
0x104 DMACC0DestAddr
0x108 DMACC0LLI
0x10C DMACC0Control
0x110 DMACC0Configuration
0x120 DMACC1SrcAddr
0x124 DMACC1DestAddr
etc
up to
0x1F0 DMACC7Configuration

and what the switch is trying to do is figure out which of
SrcAddr/DestAddr/LLI/Control/Configuration we're looking at
(it then uses the correctly calculated 'i' index to pick the
right index into the s->chan[] array for DMACC0 vs DMACC1 etc).

So the correct thing to switch on here is
(offset & 0x1f) >> 2.

thanks
-- PMM