phy: cadence: cdns-dphy: Enable lower resolutions in dphy

Enable support for data lane rates between 80-160 Mbps cdns dphy
as mentioned in TRM [0] by setting the pll_opdiv field to 16.
This change enables lower resolutions like 640x480 at 60Hz.

[0]: https://www.ti.com/lit/zip/spruil1
(Table 12-552. DPHY_TX_PLL_CTRL Register Field Descriptions)

Reviewed-by: Udit Kumar <u-kumar1@ti.com>
Reviewed-by: Devarsh Thakkar <devarsht@ti.com>
Signed-off-by: Harikrishna Shenoy <h-shenoy@ti.com>
Link: https://lore.kernel.org/r/20250807052002.717807-1-h-shenoy@ti.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Author: h-shenoy

drivers/phy/cadence/cdns-dphy.c

@@ -136,7 +136,7 @@ static int cdns_dphy_get_pll_cfg(struct cdns_dphy *dphy,
 
 	dlane_bps = opts->hs_clk_rate;
 
-	if (dlane_bps > 2500000000UL || dlane_bps < 160000000UL)
+	if (dlane_bps > 2500000000UL || dlane_bps < 80000000UL)
 		return -EINVAL;
 	else if (dlane_bps >= 1250000000)
 		cfg->pll_opdiv = 1;
@@ -146,6 +146,8 @@ static int cdns_dphy_get_pll_cfg(struct cdns_dphy *dphy,
 		cfg->pll_opdiv = 4;
 	else if (dlane_bps >= 160000000)
 		cfg->pll_opdiv = 8;
+	else if (dlane_bps >= 80000000)
+		cfg->pll_opdiv = 16;
 
 	cfg->pll_fbdiv = DIV_ROUND_UP_ULL(dlane_bps * 2 * cfg->pll_opdiv *
 					  cfg->pll_ipdiv,