drm/tilcdc: Fix setting clock divider for omap-l138

This fixes setting the clock divider on the TI OMAP-L138 LCDK board.

The clock drivers for OMAP-L138 are being covernted to the common clock framework. When this happens, clk_set_rate() will no longer return an error. However, on this SoC, the clock rate cannot actually be changed because the clock has to maintain a fixed ratio to the ARM clock. So after attempting to set the clock rate, we need to check to see if the new rate is actually close enough. If not, then follow the previous error path to adjust the divider in LCDC IP block to compensate for not being able to change the parent clock rate.

Tested working on a TI OMAP-L138 LCDK board.

Signed-off-by David Lechner <[email protected]>

---
 drivers/gpu/drm/tilcdc/tilcdc_crtc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

drivers/gpu/drm/tilcdc/tilcdc_crtc.c +1 -1

index 8bf6bb9..6931777 100644
@@ -224,7 +224,7 @@ static void tilcdc_crtc_set_clk(struct drm_crtc *crtc)
 
 	ret = clk_set_rate(priv->clk, req_rate * clkdiv);
 	clk_rate = clk_get_rate(priv->clk);
-	if (ret < 0) {
+	if (ret < 0 || tilcdc_pclk_diff(req_rate, clk_rate) > 5) {
 		/*
 		 * If we fail to set the clock rate (some architectures don't
 		 * use the common clock framework yet and may not implement

Thanks,
I'll pick this for v4.18.

Quoted 2 lines · Jyri Sarha

Thanks,
I'll pick this for v4.18.

Ping. I don't see this in drm-misc-next yet.