disp: msm: sde: avoid dsc hw allocation switch for an active display

While hw resources allocation for an active display during modeset, avoid
dsc hw allocation switch by finding which dsc encoders are allocated
previously and allocate same dsc hw encoders. This helps in fixing underrun
issues in below scenario of dual display power ON/OFF.
Use case: Dual DSI display setup, both are DSC enabled, primary in video mode.
    --> when both displays are in powered off, all hw block are free.
    --> enable second dsi display
    Since LM 0/1 marked for primary, LM 2/3 allocated along with DSC 0/1
    --> enable primary display
    LM 0/1 allocated with DSC 2/3 encoders
    --> Now power off secondary DSI
    DSC 0/1 are freed up
    --> Immediate modeset on primary, DSC allocation switched
    LM 0/1 and DSC 0/1 allocated. DSC 2/3 are freed up as per RM but
    decoupling DSC 2/3 blocks with respective pingpong or intf is not done.
    This is causing underruns on primary.
Tracking which DSC blocks are freed during resource switch and programming the
respective DSC control mux configuration is not feasible and not scalable as
any other display can allocate those blocks and would require synchronizing
across display threads. So approach taken is avoid dsc resource switch itself.

Change-Id: I7f740722a52266740c4b168edc0c619e3cf68989
Signed-off-by: Prabhanjan Kandula <[email protected]>

msm/sde/sde_rm.c

@@ -24,6 +24,9 @@
 	(((h)->rsvp && ((h)->rsvp->enc_id != (r)->enc_id)) ||\
 		((h)->rsvp_nxt && ((h)->rsvp_nxt->enc_id != (r)->enc_id)))
 
+#define RESERVED_BY_CURRENT(h, r) \
+	(((h)->rsvp && ((h)->rsvp->enc_id == (r)->enc_id)))
+
 #define RM_RQ_LOCK(r) ((r)->top_ctrl & BIT(SDE_RM_TOPCTL_RESERVE_LOCK))
 #define RM_RQ_CLEAR(r) ((r)->top_ctrl & BIT(SDE_RM_TOPCTL_RESERVE_CLEAR))
 #define RM_RQ_DSPP(r) ((r)->top_ctrl & BIT(SDE_RM_TOPCTL_DSPP))
@@ -1848,12 +1851,39 @@ static int _sde_rm_make_ctl_rsvp(struct sde_rm *rm, struct sde_rm_rsvp *rsvp,
 	return ret;
 }
 
+/*
+ * Returns number of dsc hw blocks previously  owned by this encoder.
+ * Returns 0 if not found  or error
+ */
+static int _sde_rm_find_prev_dsc(struct sde_rm *rm, struct sde_rm_rsvp *rsvp,
+		u8 *prev_dsc, u32 max_cnt)
+{
+	int i = 0;
+	struct sde_rm_hw_iter iter_dsc;
+
+	if ((!prev_dsc) || (max_cnt < MAX_DATA_PATH_PER_DSIPLAY))
+		return 0;
+
+	sde_rm_init_hw_iter(&iter_dsc, 0, SDE_HW_BLK_DSC);
+
+	while (_sde_rm_get_hw_locked(rm, &iter_dsc)) {
+		if (RESERVED_BY_CURRENT(iter_dsc.blk, rsvp))
+			prev_dsc[i++] =  iter_dsc.blk->id;
+
+		if (i >= MAX_DATA_PATH_PER_DSIPLAY)
+		       return 0;
+	}
+
+	return i;
+}
+
 static int _sde_rm_make_dsc_rsvp(struct sde_rm *rm, struct sde_rm_rsvp *rsvp,
 		struct sde_rm_requirements *reqs,
 		struct sde_splash_display *splash_display)
 {
 	int i;
 	u8 *hw_ids = NULL;
+	u8 prev_dsc[MAX_DATA_PATH_PER_DSIPLAY] = {0,};
 
 	/* Check if splash data provided dsc_ids */
 	if (splash_display) {
@@ -1866,7 +1896,16 @@ static int _sde_rm_make_dsc_rsvp(struct sde_rm *rm, struct sde_rm_rsvp *rsvp,
 				i, splash_display->dsc_ids[i]);
 	}
 
-	return  _sde_rm_reserve_dsc(rm, rsvp, reqs, hw_ids);
+	/*
+	 * find if this encoder has previously allocated dsc hw blocks, use same dsc blocks
+	 * if found to avoid switching dsc encoders during each modeset, as currently we
+	 * dont have feasible way of decoupling previously owned dsc blocks by resetting
+	 * respective dsc encoders mux control and flush them from commit path
+	 */
+	if (!hw_ids && _sde_rm_find_prev_dsc(rm, rsvp, prev_dsc, MAX_DATA_PATH_PER_DSIPLAY))
+		return  _sde_rm_reserve_dsc(rm, rsvp, reqs, prev_dsc);
+	else
+		return  _sde_rm_reserve_dsc(rm, rsvp, reqs, hw_ids);
 
 }