Re: [PATCH 09/13] dma/xlnx-zdma: Remove redundant statement in zdma_write_dst()

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 2/25/20 11:01 AM, Chenqun (kuhn) wrote:
>> -----Original Message-----
>> From: Philippe Mathieu-Daudé [mailto:philmd@redhat.com]
>> Sent: Tuesday, February 25, 2020 5:36 PM
>> To: Chenqun (kuhn) <kuhn.chenqun@huawei.com>; qemu-
>> devel@nongnu.org; qemu-trivial@nongnu.org
>> Cc: peter.maydell@linaro.org; Zhanghailiang
>> <zhang.zhanghailiang@huawei.com>; Alistair Francis <alistair@alistair23.me>;
>> qemu-arm@nongnu.org
>> Subject: Re: [PATCH 09/13] dma/xlnx-zdma: Remove redundant statement in
>> zdma_write_dst()
>>
>> On 2/25/20 3:09 AM, kuhn.chenqun@huawei.com wrote:
>>> From: Chen Qun <kuhn.chenqun@huawei.com>
>>>
>>> Clang static code analyzer show warning:
>>> hw/dma/xlnx-zdma.c:399:13: warning: Value stored to 'dst_type' is never
>> read
>>>               dst_type = FIELD_EX32(s->dsc_dst.words[3],
>> ZDMA_CH_DST_DSCR_WORD3,
>>>               ^
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>
>>> Reported-by: Euler Robot <euler.robot@huawei.com>
>>> Signed-off-by: Chen Qun <kuhn.chenqun@huawei.com>
>>> ---
>>> Cc: Alistair Francis <alistair@alistair23.me>
>>> Cc: "Edgar E. Iglesias" <edgar.iglesias@gmail.com>
>>> Cc: Peter Maydell <peter.maydell@linaro.org>
>>> Cc: qemu-arm@nongnu.org
>>> ---
>>>    hw/dma/xlnx-zdma.c | 2 --
>>>    1 file changed, 2 deletions(-)
>>>
>>> diff --git a/hw/dma/xlnx-zdma.c b/hw/dma/xlnx-zdma.c index
>>> 8fb83f5b07..45355c5d59 100644
>>> --- a/hw/dma/xlnx-zdma.c
>>> +++ b/hw/dma/xlnx-zdma.c
>>> @@ -396,8 +396,6 @@ static void zdma_write_dst(XlnxZDMA *s, uint8_t
>> *buf, uint32_t len)
>>>                zdma_load_descriptor(s, next, &s->dsc_dst);
>>>                dst_size = FIELD_EX32(s->dsc_dst.words[2],
>> ZDMA_CH_DST_DSCR_WORD2,
>>>                                      SIZE);
>>> -            dst_type = FIELD_EX32(s->dsc_dst.words[3],
>> ZDMA_CH_DST_DSCR_WORD3,
>>> -                                  TYPE);
>>
>> Maybe move dst_type to this if() statement now?
>>
> Sorry, I don't follow you.   I didn't find where I could move dst_type.
> Do you mean to move the first dst_type to the if().
> Modify it like this:
>      while (len) {
>          dst_size = FIELD_EX32(s->dsc_dst.words[2], ZDMA_CH_DST_DSCR_WORD2,
>                                SIZE);
>          if (dst_size == 0 && ptype == PT_MEM) {
>              uint64_t next;
>              dst_type = FIELD_EX32(s->dsc_dst.words[3], ZDMA_CH_DST_DSCR_WORD3,
>                                TYPE);
>              next = zdma_update_descr_addr(s, dst_type,
>                                            R_ZDMA_CH_DST_CUR_DSCR_LSB);
>              zdma_load_descriptor(s, next, &s->dsc_dst);
>              dst_size = FIELD_EX32(s->dsc_dst.words[2], ZDMA_CH_DST_DSCR_WORD2,
>                                    SIZE);
>          }
>         ...
>     }

No, like this:

-- >8 --
@@ -373,7 +373,7 @@ static uint64_t zdma_update_descr_addr(XlnxZDMA *s, 
bool type,
  static void zdma_write_dst(XlnxZDMA *s, uint8_t *buf, uint32_t len)
  {
      uint32_t dst_size, dlen;
-    bool dst_intr, dst_type;
+    bool dst_intr;
      unsigned int ptype = ARRAY_FIELD_EX32(s->regs, ZDMA_CH_CTRL0, 
POINT_TYPE);
      unsigned int rw_mode = ARRAY_FIELD_EX32(s->regs, ZDMA_CH_CTRL0, MODE);
      unsigned int burst_type = ARRAY_FIELD_EX32(s->regs, ZDMA_CH_DATA_ATTR,
@@ -387,17 +387,17 @@ static void zdma_write_dst(XlnxZDMA *s, uint8_t 
*buf, uint32_t len)
      while (len) {
          dst_size = FIELD_EX32(s->dsc_dst.words[2], ZDMA_CH_DST_DSCR_WORD2,
                                SIZE);
-        dst_type = FIELD_EX32(s->dsc_dst.words[3], ZDMA_CH_DST_DSCR_WORD3,
-                              TYPE);
          if (dst_size == 0 && ptype == PT_MEM) {
              uint64_t next;
+            bool dst_type;
+
+            dst_type = FIELD_EX32(s->dsc_dst.words[3], 
ZDMA_CH_DST_DSCR_WORD3,
+                                  TYPE);
              next = zdma_update_descr_addr(s, dst_type,
                                            R_ZDMA_CH_DST_CUR_DSCR_LSB);
              zdma_load_descriptor(s, next, &s->dsc_dst);
              dst_size = FIELD_EX32(s->dsc_dst.words[2], 
ZDMA_CH_DST_DSCR_WORD2,
                                    SIZE);
-            dst_type = FIELD_EX32(s->dsc_dst.words[3], 
ZDMA_CH_DST_DSCR_WORD3,
-                                  TYPE);
          }
---