[[RFC PATCH] Trim 1204 bytes from gm204_grctx_generate_405b60 stack frame

[George Spelvin]

This function keeps causing the kernel build to whine at me about
its 1200 byte stack frame.

(TPC_MAC = 8 * GPC_MAX = 8 * 32 = 256)

The following generates the same nv_wr32() operations in the same
order as the original, but without the 256-word dist[] array.

(I'm not sure if 4-bit fields inside the dist bytes can accomodate
priv->gpc_nr greater than 16, so the other arrays could have halved
in size, too, but that's a separate issue.)

I don't have the necessary hardware to test this, but would
someone mind doing so?

(If you want to declare *priv const while you're at it, I'm not likely
to object.)

Signed-off-by: George Spelvin <linux at horizon.com>
---
 drivers/gpu/drm/nouveau/nvkm/engine/gr/ctxgm204.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/gr/ctxgm204.c b/drivers/gpu/drm/nouveau/nvkm/engine/gr/ctxgm204.c
index ea8e6615..00aa4a8b 100644
--- a/drivers/gpu/drm/nouveau/nvkm/engine/gr/ctxgm204.c
+++ b/drivers/gpu/drm/nouveau/nvkm/engine/gr/ctxgm204.c
@@ -946,8 +946,7 @@ gm204_grctx_generate_rop_active_fbps(struct gf100_gr_priv *priv)
 static void
 gm204_grctx_generate_405b60(struct gf100_gr_priv *priv)
 {
-	const u32 dist_nr = DIV_ROUND_UP(priv->tpc_total, 4);
-	u32 dist[TPC_MAX] = {};
+	u32 dist = 0;
 	u32 gpcs[GPC_MAX] = {};
 	u8  tpcnr[GPC_MAX];
 	int tpc, gpc, i;
@@ -964,12 +963,16 @@ gm204_grctx_generate_405b60(struct gf100_gr_priv *priv)
 		} while(!tpcnr[gpc]);
 		tpc = priv->tpc_nr[gpc] - tpcnr[gpc]--;
 
-		dist[i / 4] |= ((gpc << 4) | tpc) << ((i % 4) * 8);
+		dist |= ((gpc << 4) | tpc) << ((i % 4) * 8);
+		if ((i % 4) == 3) {
+			nv_wr32(priv, 0x405b60 + i - 3, dist);
+			dist = 0;
+		}
 		gpcs[gpc] |= i << (tpc * 8);
 	}
+	if (i % 4)
+		nv_wr32(priv, 0x405b60 + round_down(i, 4), dist);
 
-	for (i = 0; i < dist_nr; i++)
-		nv_wr32(priv, 0x405b60 + (i * 4), dist[i]);
 	for (i = 0; i < priv->gpc_nr; i++)
 		nv_wr32(priv, 0x405ba0 + (i * 4), gpcs[i]);
 }