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H A D | clk-imx6q.c | diff 5d283b083800867dc329e6433576664bf0fc18d5 Tue Oct 18 02:29:14 CEST 2016 Fabio Estevam <fabio.estevam@nxp.com> clk: imx6: Fix procedure to switch the parent of LDB_DI_CLK
Due to incorrect placement of the clock gate cell in the ldb_di[x]_clk tree, the glitchy parent mux of ldb_di[x]_clk can cause a glitch to enter the ldb_di_ipu_div divider. If the divider gets locked up, no ldb_di[x]_clk is generated, and the LVDS display will hang when the ipu_di_clk is sourced from ldb_di_clk.
To fix the problem, both the new and current parent of the ldb_di_clk should be disabled before the switch. This patch ensures that correct steps are followed when ldb_di_clk parent is switched in the beginning of boot. The glitchy muxes are then registered as read-only. The clock parent can be selected using the assigned-clocks and assigned-clock-parents properties of the ccm device tree node:
&clks { assigned-clocks = <&clks IMX6QDL_CLK_LDB_DI0_SEL>, <&clks IMX6QDL_CLK_LDB_DI1_SEL>; assigned-clock-parents = <&clks IMX6QDL_CLK_MMDC_CH1_AXI>, <&clks IMX6QDL_CLK_PLL5_VIDEO_DIV>; };
The issue is explained in detail in EB821 ("LDB Clock Switch Procedure & i.MX6 Asynchronous Clock Switching Guidelines") [1].
[1] http://www.nxp.com/files/32bit/doc/eng_bulletin/EB821.pdf
Signed-off-by: Ranjani Vaidyanathan <Ranjani.Vaidyanathan@nxp.com> Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com> Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de> Reviewed-by: Akshay Bhat <akshay.bhat@timesys.com> Tested-by Joshua Clayton <stillcompiling@gmail.com> Tested-by: Charles Kang <Charles.Kang@advantech.com.tw> Signed-off-by: Shawn Guo <shawnguo@kernel.org>
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