[PATCH v2 2/6] drm/xe: Use iosys_map helpers for WA BB emission
Tvrtko Ursulin
tvrtko.ursulin at igalia.com
Mon Jun 2 15:22:47 UTC 2025
On 02/06/2025 15:56, Lucas De Marchi wrote:
> On Mon, Jun 02, 2025 at 12:19:52PM +0100, Tvrtko Ursulin wrote:
>> To properly support discrete GPUs on all platforms it is required to use
>> the iosys_map helpers.
>>
>> To fix we emit the WA BB into an on stack buffer and copy it over using
>> xe_map_memcpy_to().
>
> For https://lore.kernel.org/intel-xe/20250523-wa-bb-cmds-
> v1-0-40b337f71bcd at intel.com
> we will extend the WA BB to other things (and that is the first
> additional user). I don't think we can keep it on stack. For my next
> version I was adding the patch below to allocate the buffer. Let me know
> what you think.
Works for me I think.
I mean I don't exactly see yet how you will make it work for multiple
users adding stuff to the same wa bb, like will you consider a shared
buffer passed down from the level up or what, but in any case I can
probably adapt my series quite easily.
In summary, you suggest my series waits for yours to land first?
Regards,
Tvrtko
> commit 28dbdf201133d92b0e0b0a0139eae7fe5eb9e33b
> Author: Lucas De Marchi <lucas.demarchi at intel.com>
> Date: Fri May 30 16:29:51 2025 -0700
>
> drm/xe/lrc: Use a temporary buffer for WA BB
> In case the BO is in iomem, we can't simply take the vaddr and
> write to
> it. Instead, prepare a separate buffer that is later copied into io
> memory. Right now it's just a few words that could be using
> xe_map_write32(), but the intention is to grow the WA BB for other
> uses.
> Fixes: 82b98cadb01f ("drm/xe: Add WA BB to capture active context
> utilization")
> Cc: Umesh Nerlige Ramappa <umesh.nerlige.ramappa at intel.com>
> Signed-off-by: Lucas De Marchi <lucas.demarchi at intel.com>
>
> diff --git a/drivers/gpu/drm/xe/xe_lrc.c b/drivers/gpu/drm/xe/xe_lrc.c
> index 63d74e27f54cf..1b835d7efca2b 100644
> --- a/drivers/gpu/drm/xe/xe_lrc.c
> +++ b/drivers/gpu/drm/xe/xe_lrc.c
> @@ -941,11 +941,18 @@ static void xe_lrc_finish(struct xe_lrc *lrc)
> * store it in the PPHSWP.
> */
> #define CONTEXT_ACTIVE 1ULL
> -static void xe_lrc_setup_utilization(struct xe_lrc *lrc)
> +static int xe_lrc_setup_utilization(struct xe_lrc *lrc)
> {
> - u32 *cmd;
> + u32 *cmd, *buf = NULL;
>
> - cmd = lrc->bb_per_ctx_bo->vmap.vaddr;
> + if (lrc->bb_per_ctx_bo->vmap.is_iomem) {
> + buf = kmalloc(lrc->bb_per_ctx_bo->size, GFP_KERNEL);
> + if (!buf)
> + return -ENOMEM;
> + cmd = buf;
> + } else {
> + cmd = lrc->bb_per_ctx_bo->vmap.vaddr;
> + }
>
> *cmd++ = MI_STORE_REGISTER_MEM | MI_SRM_USE_GGTT |
> MI_SRM_ADD_CS_OFFSET;
> *cmd++ = ENGINE_ID(0).addr;
> @@ -966,9 +973,16 @@ static void xe_lrc_setup_utilization(struct xe_lrc
> *lrc)
>
> *cmd++ = MI_BATCH_BUFFER_END;
>
> + if (buf) {
> + xe_map_memcpy_to(gt_to_xe(lrc->gt), &lrc->bb_per_ctx_bo->vmap, 0,
> + buf, cmd - buf);
> + kfree(buf);
> + }
> +
> xe_lrc_write_ctx_reg(lrc, CTX_BB_PER_CTX_PTR,
> xe_bo_ggtt_addr(lrc->bb_per_ctx_bo) | 1);
>
> + return 0;
> }
>
> #define PVC_CTX_ASID (0x2e + 1)
> @@ -1125,7 +1139,9 @@ static int xe_lrc_init(struct xe_lrc *lrc, struct
> xe_hw_engine *hwe,
> map = __xe_lrc_start_seqno_map(lrc);
> xe_map_write32(lrc_to_xe(lrc), &map, lrc->fence_ctx.next_seqno - 1);
>
> - xe_lrc_setup_utilization(lrc);
> + err = xe_lrc_setup_utilization(lrc);
> + if (err)
> + goto err_lrc_finish;
>
> return 0;
>
> Lucas De Marchi
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