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authorFabio Estevam <fabio.estevam@nxp.com>2016-01-19 11:10:57 -0200
committerTomi Valkeinen <tomi.valkeinen@ti.com>2016-01-29 14:20:16 +0200
commitb82fe6ddd782f847332aeabf8cab980852f61629 (patch)
tree97d53f9e7ef82d6640e12fa63fe3bf9ec4e5d4b3 /drivers/video/fbdev/imxfb.c
parentc3a2da26e6216033456c1d5375cd1d2629d1fd09 (diff)
video: fbdev: imxfb: Provide a reset mechanism
Currently when we boot the kernel on a mx25pdk the LCDC controller does not show the Linux logo on boot. This problem is well explained by Sascha Hauer: "Unfortunately this LCD controller does not have an enable bit. The controller starts directly when the clocks are enabled. If the clocks are enabled when the controller is not yet programmed with proper register values then it just goes into some undefined state. What I suspect is that the clocks already were enabled before driver probe, presumably by the bootloader, so the controller is already in undefined state when entering Linux. Now by dis/enabling the ipg clock you effectively reset the controller. Since you have programmed it with valid register values in the mean time it starts working after this reset." So do as suggested and force a reset of the LCDC hardware by enabling and disabling the IPG clock. With this change the Linux logo can be seen on boot on a mx25pdk. Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Diffstat (limited to 'drivers/video/fbdev/imxfb.c')
-rw-r--r--drivers/video/fbdev/imxfb.c15
1 files changed, 15 insertions, 0 deletions
diff --git a/drivers/video/fbdev/imxfb.c b/drivers/video/fbdev/imxfb.c
index cee88603efc9..bb2f1e866020 100644
--- a/drivers/video/fbdev/imxfb.c
+++ b/drivers/video/fbdev/imxfb.c
@@ -902,6 +902,21 @@ static int imxfb_probe(struct platform_device *pdev)
goto failed_getclock;
}
+ /*
+ * The LCDC controller does not have an enable bit. The
+ * controller starts directly when the clocks are enabled.
+ * If the clocks are enabled when the controller is not yet
+ * programmed with proper register values (enabled at the
+ * bootloader, for example) then it just goes into some undefined
+ * state.
+ * To avoid this issue, let's enable and disable LCDC IPG clock
+ * so that we force some kind of 'reset' to the LCDC block.
+ */
+ ret = clk_prepare_enable(fbi->clk_ipg);
+ if (ret)
+ goto failed_getclock;
+ clk_disable_unprepare(fbi->clk_ipg);
+
fbi->clk_ahb = devm_clk_get(&pdev->dev, "ahb");
if (IS_ERR(fbi->clk_ahb)) {
ret = PTR_ERR(fbi->clk_ahb);