The DI pixel clock divider bit field is only 8 bits wide for the
integer part, so limit the divider to the 1...255 interval before
deciding whether the internal clock can be used and before writing
to the register.

Reported-by: Felix Mellmann <felix.mellmann at gmail.com>
Signed-off-by: Philipp Zabel <p.zabel at pengutronix.de>
---
 drivers/gpu/ipu-v3/ipu-di.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/ipu-v3/ipu-di.c b/drivers/gpu/ipu-v3/ipu-di.c
index 6607cc8..247871f 100644
--- a/drivers/gpu/ipu-v3/ipu-di.c
+++ b/drivers/gpu/ipu-v3/ipu-di.c
@@ -519,8 +519,7 @@ static void ipu_di_config_clock(struct ipu_di *di,

                        in_rate = clk_get_rate(clk);
                        div = DIV_ROUND_CLOSEST(in_rate, sig->mode.pixelclock);
-                       if (div == 0)
-                               div = 1;
+                       div = clamp(div, 1U, 255U);

                        clkgen0 = div << 4;
                }
@@ -537,8 +536,7 @@ static void ipu_di_config_clock(struct ipu_di *di,

                clkrate = clk_get_rate(di->clk_ipu);
                div = DIV_ROUND_CLOSEST(clkrate, sig->mode.pixelclock);
-               if (div == 0)
-                       div = 1;
+               div = clamp(div, 1U, 255U);
                rate = clkrate / div;

                error = rate / (sig->mode.pixelclock / 1000);
@@ -561,8 +559,7 @@ static void ipu_di_config_clock(struct ipu_di *di,

                        in_rate = clk_get_rate(clk);
                        div = DIV_ROUND_CLOSEST(in_rate, sig->mode.pixelclock);
-                       if (div == 0)
-                               div = 1;
+                       div = clamp(div, 1U, 255U);

                        clkgen0 = div << 4;
                }
-- 
2.1.4

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