[PATCH v8 3/7] drm/xe: Return number of written dwords from workaround batch buffer emission

[Tvrtko Ursulin]

On 08/07/2025 23:11, Lucas De Marchi wrote:
> On Thu, Jul 03, 2025 at 09:20:55AM +0100, Tvrtko Ursulin wrote:
>> Indirect context setup will need to get to the number of written dwords.
>> Lets add it as an output parameter so it can be accessed from the caller
>> regardless of whether code is writing directly or via an shadow buffer.
>>
>> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at igalia.com>
>> Cc: Lucas De Marchi <lucas.demarchi at intel.com>
>> ---
>> drivers/gpu/drm/xe/xe_lrc.c | 16 +++++++++++-----
>> 1 file changed, 11 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_lrc.c b/drivers/gpu/drm/xe/xe_lrc.c
>> index edd8751b164a..7f8911a10cc9 100644
>> --- a/drivers/gpu/drm/xe/xe_lrc.c
>> +++ b/drivers/gpu/drm/xe/xe_lrc.c
>> @@ -985,7 +985,8 @@ setup_bo(struct xe_lrc *lrc,
>>      unsigned int offset,
>>      const struct bo_setup *funcs,
>>      unsigned int num_funcs,
>> -     u32 **free)
>> +     u32 **free,
>> +     unsigned int *written)
>> {
>>     u32 *cmd, *buf = NULL;
>>     ssize_t remain;
>> @@ -1016,6 +1017,8 @@ setup_bo(struct xe_lrc *lrc,
>>             goto fail;
>>
>>         cmd += len;
>> +        if (written)
>> +            *written += len;
>>     }
>>
>>     return cmd;
>> @@ -1026,13 +1029,14 @@ setup_bo(struct xe_lrc *lrc,
>> }
>>
>> static void
>> -finish_bo(struct xe_lrc *lrc, unsigned int offset, u32 *cmd, u32 *free)
>> +finish_bo(struct xe_lrc *lrc, unsigned int offset, unsigned int written,
>> +      u32 *free)
>> {
>>     if (!free)
>>         return;
>>
>>     xe_map_memcpy_to(gt_to_xe(lrc->gt), &lrc->bo->vmap, offset, free,
>> -             (cmd - free) * sizeof(*cmd));
>> +             written * sizeof(u32));
>>     kfree(free);
>> }
>>
>> @@ -1042,16 +1046,18 @@ static int setup_wa_bb(struct xe_lrc *lrc, 
>> struct xe_hw_engine *hwe)
>>         { .setup = setup_utilization_wa },
>>     };
>>     unsigned int offset = __xe_lrc_wa_bb_offset(lrc);
>> +    unsigned int written = 0;
>>     u32 *cmd, *buf = NULL;
>>
>>     cmd = setup_bo(lrc, hwe, LRC_WA_BB_SIZE, offset, funcs,
>> -               ARRAY_SIZE(funcs), &buf);
>> +               ARRAY_SIZE(funcs), &buf, &written);
>>     if (IS_ERR(cmd))
>>         return PTR_ERR(cmd);
>>
>>     *cmd++ = MI_BATCH_BUFFER_END;
>> +    written++;
>>
>> -    finish_bo(lrc, offset, cmd, buf);
>> +    finish_bo(lrc, offset, written, buf);
> 
> we should still have cmd in this call, right? But in the next patch the
> cmd should be gone as it's then unused.

No, it is already unused in this patch. Explicitly counting dwords 
written replaced the "end - start" pointer arithmetic.

Regards,

Tvrtko

> 
> Lucas De Marchi
> 
>>
>>     xe_lrc_write_ctx_reg(lrc, CTX_BB_PER_CTX_PTR,
>>                  xe_bo_ggtt_addr(lrc->bo) + offset + 1);
>> -- 
>> 2.48.0
>>