[PATCH V8 3/7] drm: bridge: samsung-dsim: Fetch pll-clock-frequency automatically

[Adam Ford]

Make the pll-clock-frequency optional.  If it's present, use it
to maintain backwards compatibility with existing hardware.  If it
is absent, read clock rate of "sclk_mipi" to determine the rate.
Since it can be optional, change the message from an error to
dev_info.

Signed-off-by: Adam Ford <aford...@gmail.com>
Tested-by: Chen-Yu Tsai <we...@chromium.org>
Tested-by: Frieder Schrempf <frieder.schre...@kontron.de>
Reviewed-by: Frieder Schrempf <frieder.schre...@kontron.de>
Tested-by: Marek Szyprowski <m.szyprow...@samsung.com>
Reviewed-by: Jagan Teki <ja...@amarulasolutions.com>
Tested-by: Jagan Teki <ja...@amarulasolutions.com> # imx8mm-icore
---
 drivers/gpu/drm/bridge/samsung-dsim.c | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c 
b/drivers/gpu/drm/bridge/samsung-dsim.c
index ead922c3ce9f..307f1c20cfb9 100644
--- a/drivers/gpu/drm/bridge/samsung-dsim.c
+++ b/drivers/gpu/drm/bridge/samsung-dsim.c
@@ -1719,11 +1719,11 @@ static const struct mipi_dsi_host_ops samsung_dsim_ops 
= {
 };
 
 static int samsung_dsim_of_read_u32(const struct device_node *np,
-                                   const char *propname, u32 *out_value)
+                                   const char *propname, u32 *out_value, bool 
optional)
 {
        int ret = of_property_read_u32(np, propname, out_value);
 
-       if (ret < 0)
+       if (ret < 0 && !optional)
                pr_err("%pOF: failed to get '%s' property\n", np, propname);
 
        return ret;
@@ -1736,19 +1736,27 @@ static int samsung_dsim_parse_dt(struct samsung_dsim 
*dsi)
        u32 lane_polarities[5] = { 0 };
        struct device_node *endpoint;
        int i, nr_lanes, ret;
+       struct clk *pll_clk;
 
        ret = samsung_dsim_of_read_u32(node, "samsung,pll-clock-frequency",
-                                      &dsi->pll_clk_rate);
-       if (ret < 0)
-               return ret;
+                                      &dsi->pll_clk_rate, 1);
+       /* If it doesn't exist, read it from the clock instead of failing */
+       if (ret < 0) {
+               dev_dbg(dev, "Using sclk_mipi for pll clock frequency\n");
+               pll_clk = devm_clk_get(dev, "sclk_mipi");
+               if (!IS_ERR(pll_clk))
+                       dsi->pll_clk_rate = clk_get_rate(pll_clk);
+               else
+                       return PTR_ERR(pll_clk);
+       }
 
        ret = samsung_dsim_of_read_u32(node, "samsung,burst-clock-frequency",
-                                      &dsi->burst_clk_rate);
+                                      &dsi->burst_clk_rate, 0);
        if (ret < 0)
                return ret;
 
        ret = samsung_dsim_of_read_u32(node, "samsung,esc-clock-frequency",
-                                      &dsi->esc_clk_rate);
+                                      &dsi->esc_clk_rate, 0);
        if (ret < 0)
                return ret;
 
-- 
2.39.2