On Tue, May 20, 2025 at 10:01:59AM +0100, Tvrtko Ursulin wrote:
Hi,
One question below in the context of the missing workarounds series I
am working on:
On 09/05/2025 17:12, Umesh Nerlige Ramappa wrote:
8><
+#define CONTEXT_ACTIVE 1ULL
+static void xe_lrc_setup_utilization(struct xe_lrc *lrc)
+{
+ u32 *cmd;
+
+ 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;
+ *cmd++ = __xe_lrc_engine_id_ggtt_addr(lrc);
+ *cmd++ = 0;
+
+ *cmd++ = MI_STORE_DATA_IMM | MI_SDI_GGTT | MI_SDI_NUM_DW(1);
+ *cmd++ = __xe_lrc_ctx_timestamp_ggtt_addr(lrc);
+ *cmd++ = 0;
+ *cmd++ = lower_32_bits(CONTEXT_ACTIVE);
+
+ if (lrc_to_xe(lrc)->info.has_64bit_timestamp) {
+ *cmd++ = MI_STORE_DATA_IMM | MI_SDI_GGTT | MI_SDI_NUM_DW(1);
+ *cmd++ = __xe_lrc_ctx_timestamp_udw_ggtt_addr(lrc);
+ *cmd++ = 0;
+ *cmd++ = upper_32_bits(CONTEXT_ACTIVE);
+ }
+
+ *cmd++ = MI_BATCH_BUFFER_END;
Matt Roper raised the suggestion in another series that we should
always use the iosys helpers for writing into mapped BOs. Later I
realised this code uses the same shortcut as I did. I probably even
lifted the concept since I placed my function right next to this one.
:)
So question is what is the definitive recommended way to write into
mapped BOs? Is the direct writes shortcut acceptable, or this also
needs changing?
right, I missed that during review. We may have a problem in !x86 if we
have __iomem here. So yes, we need to change. So probably:
cmd = &lrc->bb_per_ctx_bo->vmap;
xe_map_write32(xe, cmd, MI_STORE_REGISTER_MEM | MI_SRM_USE_GGTT |
MI_SRM_ADD_CS_OFFSET);
xe_map_write32(xe, cmd, ENGINE_ID(0).addr);
...
maybe we could add an iosys_map_wr_many() that would be a variadic
version with offset incr and hopefully the check for is_iomem in a
single place. Another option would be a local buffer that we memcpy at
the end.
+Thomas Zimmerman / +Sima
Lucas De Marchi
+
+ xe_lrc_write_ctx_reg(lrc, CTX_BB_PER_CTX_PTR,
+ xe_bo_ggtt_addr(lrc->bb_per_ctx_bo) | 1);
Btw here code uses the iosys helpers. It is a different BO but they
are created/mapped the same AFAICT.
Regards,
Tvrtko
