Re: [Qemu-devel] [PATCH 03/14] sdhci: use the ldst_le_dma() API

[Alistair Francis]

On Thu, Dec 14, 2017 at 3:21 PM, Philippe Mathieu-Daudé <address@hidden> wrote:
> On Thu, Dec 14, 2017 at 2:23 PM, Alistair Francis
> <address@hidden> wrote:
>> On Wed, Dec 13, 2017 at 11:58 AM, Philippe Mathieu-Daudé
>> <address@hidden> wrote:
>>> This makes the code slightly safer, also easier to review.
>>>
>>> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
>>> ---
>>>  hw/sd/sdhci.c | 23 +++++++----------------
>>>  1 file changed, 7 insertions(+), 16 deletions(-)
>>>
>>> diff --git a/hw/sd/sdhci.c b/hw/sd/sdhci.c
>>> index 312b167bfa..e39623baba 100644
>>> --- a/hw/sd/sdhci.c
>>> +++ b/hw/sd/sdhci.c
>>> @@ -603,14 +603,12 @@ typedef struct ADMADescr {
>>>
>>>  static void get_adma_description(SDHCIState *s, ADMADescr *dscr)
>>>  {
>>> -    uint32_t adma1 = 0;
>>> -    uint64_t adma2 = 0;
>>> +    uint32_t adma1;
>>> +    uint64_t adma2;
>>>      hwaddr entry_addr = (hwaddr)s->admasysaddr;
>>>      switch (SDHC_DMA_TYPE(s->hostctl)) {
>>>      case SDHC_CTRL_ADMA2_32:
>>> -        dma_memory_read(&address_space_memory, entry_addr, (uint8_t 
>>> *)&adma2,
>>> -                        sizeof(adma2));
>>> -        adma2 = le64_to_cpu(adma2);
>>> +        adma2 = ldq_le_dma(&address_space_memory, entry_addr);
>>>          /* The spec does not specify endianness of descriptor table.
>>>           * We currently assume that it is LE.
>>>           */
>>> @@ -620,9 +618,7 @@ static void get_adma_description(SDHCIState *s, 
>>> ADMADescr *dscr)
>>>          dscr->incr = 8;
>>>          break;
>>>      case SDHC_CTRL_ADMA1_32:
>>> -        dma_memory_read(&address_space_memory, entry_addr, (uint8_t 
>>> *)&adma1,
>>> -                        sizeof(adma1));
>>> -        adma1 = le32_to_cpu(adma1);
>>> +        adma1 = ldl_le_dma(&address_space_memory, entry_addr);
>>>          dscr->addr = (hwaddr)(adma1 & 0xFFFFF000);
>>>          dscr->attr = (uint8_t)extract32(adma1, 0, 7);
>>>          dscr->incr = 4;
>>> @@ -633,14 +629,9 @@ static void get_adma_description(SDHCIState *s, 
>>> ADMADescr *dscr)
>>>          }
>>>          break;
>>>      case SDHC_CTRL_ADMA2_64:
>>> -        dma_memory_read(&address_space_memory, entry_addr,
>>> -                        (uint8_t *)(&dscr->attr), 1);
>>> -        dma_memory_read(&address_space_memory, entry_addr + 2,
>>> -                        (uint8_t *)(&dscr->length), 2);
>>> -        dscr->length = le16_to_cpu(dscr->length);
>>> -        dma_memory_read(&address_space_memory, entry_addr + 4,
>>> -                        (uint8_t *)(&dscr->addr), 8);
>>> -        dscr->attr = le64_to_cpu(dscr->attr);
>>
>>> +        dscr->attr = ldub_dma(&address_space_memory, entry_addr);
>>> +        dscr->length = lduw_le_dma(&address_space_memory, entry_addr + 2);
>>> +        dscr->attr = ldq_le_dma(&address_space_memory, entry_addr + 4);
>>
>> Why this is being overwritten?
>
> Do you mean 'rewritten'?
>
>> It looks like you have dropped an addr as well.
>
> Which addr? The diff is a bit compressed, if you separate it is more obvious:
>
>  -        dma_memory_read(&address_space_memory, entry_addr,
>  -                        (uint8_t *)(&dscr->attr), 1);
>  +        dscr->attr = ldub_dma(&address_space_memory, entry_addr);

This is rewritten later, why bother setting this here?

>
>
>  -        dma_memory_read(&address_space_memory, entry_addr + 2,
>  -                        (uint8_t *)(&dscr->length), 2);
>  -        dscr->length = le16_to_cpu(dscr->length);
>  +        dscr->length = lduw_le_dma(&address_space_memory, entry_addr + 2);
>
>
>  -        dma_memory_read(&address_space_memory, entry_addr + 4,
>  -                        (uint8_t *)(&dscr->addr), 8);

What about dscr->addr which is set here?

Alistair

>  -        dscr->attr = le64_to_cpu(dscr->attr);
>  +        dscr->attr = ldq_le_dma(&address_space_memory, entry_addr + 4);
>
> The API is detailled in this file: docs/devel/loads-stores.rst
>
> I decided to rewrite this code with this API because it looks easier
> to understand (maybe once you read the API doc), so easier to review
> :)
>