OMAP: DSS2: DISPC: Fix minimum PCD value

The current driver had a hardcoded minimum value of 2 for pixel clock
divisor (PCD). This doesn't seem to be right.

OMAP4 TRM says that PCD can be 1 when not downscaling, and inverted
pixel clock (IPC) is off.

OMAP3 TRM says the same, but also in the register descriptions that PCD
value 1 is invalid.

OMAP2 TRM says PCD 2 is the minimum.

OMAP2 is still untested, but for both OMAP3 and OMAP4 PCD of 1 seems to
work fine.

This patch adds a new DSS feature, FEAT_PARAM_DSS_PCD, which is used to
find the minimum and maximum PCD. The minimum is set to 2 for OMAP2, and
1 for OMAP3/4.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

3 files changed, 14 insertions, 4 deletions

diff --git a/drivers/video/omap2/dss/dispc.c b/drivers/video/omap2/dss/dispc.c
index b4a16cf9be1c..4e9f87fc33d8 100644
--- a/drivers/video/omap2/dss/dispc.c
+++ b/drivers/video/omap2/dss/dispc.c
@@ -2334,7 +2334,7 @@ static void dispc_mgr_set_lcd_divisor(enum omap_channel channel, u16 lck_div,
                 u16 pck_div)
 {
         BUG_ON(lck_div < 1);
-        BUG_ON(pck_div < 2);
+        BUG_ON(pck_div < 1);
 
         dispc_write_reg(DISPC_DIVISORo(channel),
                         FLD_VAL(lck_div, 23, 16) | FLD_VAL(pck_div, 7, 0));
@@ -2721,11 +2721,17 @@ void dispc_mgr_set_pol_freq(enum omap_channel channel,
 void dispc_find_clk_divs(bool is_tft, unsigned long req_pck, unsigned long fck,
                 struct dispc_clock_info *cinfo)
 {
-        u16 pcd_min = is_tft ? 2 : 3;
+        u16 pcd_min, pcd_max;
         unsigned long best_pck;
         u16 best_ld, cur_ld;
         u16 best_pd, cur_pd;
 
+        pcd_min = dss_feat_get_param_min(FEAT_PARAM_DSS_PCD);
+        pcd_max = dss_feat_get_param_max(FEAT_PARAM_DSS_PCD);
+
+        if (!is_tft)
+                pcd_min = 3;
+
         best_pck = 0;
         best_ld = 0;
         best_pd = 0;
@@ -2733,7 +2739,7 @@ void dispc_find_clk_divs(bool is_tft, unsigned long req_pck, unsigned long fck,
         for (cur_ld = 1; cur_ld <= 255; ++cur_ld) {
                 unsigned long lck = fck / cur_ld;
 
-                for (cur_pd = pcd_min; cur_pd <= 255; ++cur_pd) {
+                for (cur_pd = pcd_min; cur_pd <= pcd_max; ++cur_pd) {
                         unsigned long pck = lck / cur_pd;
                         long old_delta = abs(best_pck - req_pck);
                         long new_delta = abs(pck - req_pck);
@@ -2768,7 +2774,7 @@ int dispc_calc_clock_rates(unsigned long dispc_fclk_rate,
 {
         if (cinfo->lck_div > 255 || cinfo->lck_div == 0)
                 return -EINVAL;
-        if (cinfo->pck_div < 2 || cinfo->pck_div > 255)
+        if (cinfo->pck_div < 1 || cinfo->pck_div > 255)
                 return -EINVAL;
 
         cinfo->lck = dispc_fclk_rate / cinfo->lck_div;
diff --git a/drivers/video/omap2/dss/dss_features.c b/drivers/video/omap2/dss/dss_features.c
index 86706123a247..076f399a9153 100644
--- a/drivers/video/omap2/dss/dss_features.c
+++ b/drivers/video/omap2/dss/dss_features.c
@@ -281,6 +281,7 @@ static const char * const omap4_dss_clk_source_names[] = {
 
 static const struct dss_param_range omap2_dss_param_range[] = {
         [FEAT_PARAM_DSS_FCK]                    = { 0, 173000000 },
+        [FEAT_PARAM_DSS_PCD]                    = { 2, 255 },
         [FEAT_PARAM_DSIPLL_REGN]                = { 0, 0 },
         [FEAT_PARAM_DSIPLL_REGM]                = { 0, 0 },
         [FEAT_PARAM_DSIPLL_REGM_DISPC]          = { 0, 0 },
@@ -291,6 +292,7 @@ static const struct dss_param_range omap2_dss_param_range[] = {
 
 static const struct dss_param_range omap3_dss_param_range[] = {
         [FEAT_PARAM_DSS_FCK]                    = { 0, 173000000 },
+        [FEAT_PARAM_DSS_PCD]                    = { 1, 255 },
         [FEAT_PARAM_DSIPLL_REGN]                = { 0, (1 << 7) - 1 },
         [FEAT_PARAM_DSIPLL_REGM]                = { 0, (1 << 11) - 1 },
         [FEAT_PARAM_DSIPLL_REGM_DISPC]          = { 0, (1 << 4) - 1 },
@@ -301,6 +303,7 @@ static const struct dss_param_range omap3_dss_param_range[] = {
 
 static const struct dss_param_range omap4_dss_param_range[] = {
         [FEAT_PARAM_DSS_FCK]                    = { 0, 186000000 },
+        [FEAT_PARAM_DSS_PCD]                    = { 1, 255 },
         [FEAT_PARAM_DSIPLL_REGN]                = { 0, (1 << 8) - 1 },
         [FEAT_PARAM_DSIPLL_REGM]                = { 0, (1 << 12) - 1 },
         [FEAT_PARAM_DSIPLL_REGM_DISPC]          = { 0, (1 << 5) - 1 },
diff --git a/drivers/video/omap2/dss/dss_features.h b/drivers/video/omap2/dss/dss_features.h
index c4321908f322..f73585e09d27 100644
--- a/drivers/video/omap2/dss/dss_features.h
+++ b/drivers/video/omap2/dss/dss_features.h
@@ -77,6 +77,7 @@ enum dss_feat_reg_field {
 
 enum dss_range_param {
         FEAT_PARAM_DSS_FCK,
+        FEAT_PARAM_DSS_PCD,
         FEAT_PARAM_DSIPLL_REGN,
         FEAT_PARAM_DSIPLL_REGM,
         FEAT_PARAM_DSIPLL_REGM_DISPC,