On 09/23, Fabio Estevam wrote:

Hi Stephen,

On Fri, Sep 16, 2016 at 11:36 AM, Fabio Estevam [off-list ref] wrote:

quoted

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 <redacted>
Signed-off-by: Fabio Estevam <redacted>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Akshay Bhat <redacted>
Tested-by Joshua Clayton [off-list ref]
Tested-by: Charles Kang <redacted>
Acked-by: Shawn Guo <shawnguo@kernel.org>

Do you think this one could be applied to clk-next? It fixes an
important LVDS bug.

Urgh, sorry I missed this one and then we got too close to the
merge window to keep applying things and I was traveling for a
bit. Is this a bug that's urgent and needs to be fixed to keep
these boards working in the v4.9-rc series? Does it need to go
back to stable? The change is fairly large, so we might be able
to put it into clk-fixes for -rc2, but it would need some
justification and preferably a stable/fixes tag.

Also, what about the other two patches in this series?

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