From: akshay.bhat@timesys•com (Akshay Bhat)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v5 3/3] clk: imx6: Fix procedure to switch the parent of LDB_DI_CLK
Date: Mon, 11 Jul 2016 10:41:18 -0400 [thread overview]
Message-ID: <5783B00E.7080105@timesys.com> (raw)
In-Reply-To: <1468235521-3163-3-git-send-email-p.zabel@pengutronix.de>
On 07/11/2016 07:12 AM, Philipp Zabel wrote:
> From: Fabio Estevam<fabio.estevam@freescale•com>
>
> 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@freescale•com>
> Signed-off-by: Fabio Estevam<fabio.estevam@freescale•com>
> Signed-off-by: Philipp Zabel<p.zabel@pengutronix•de>
> ---
Reviewed-by: Akshay Bhat <akshay.bhat@timesys•com>
Thanks.
next prev parent reply other threads:[~2016-07-11 14:41 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-11 11:11 [PATCH v5 1/3] clk: imx6: Mask mmdc_ch1 handshake for periph2_sel and mmdc_ch1_axi_podf Philipp Zabel
2016-07-11 11:12 ` [PATCH v5 2/3] clk: imx6: Make the LDB_DI0 and LDB_DI1 clocks read-only Philipp Zabel
2016-07-11 11:12 ` [PATCH v5 3/3] clk: imx6: Fix procedure to switch the parent of LDB_DI_CLK Philipp Zabel
2016-07-11 14:41 ` Akshay Bhat [this message]
2016-07-12 17:00 ` Fabio Estevam
2016-07-14 17:01 ` Joshua Clayton
2016-07-16 20:55 ` Joshua Clayton
2016-07-19 11:13 ` Fabio Estevam
2016-09-12 15:09 ` Akshay Bhat
2016-09-12 15:15 ` Fabio Estevam
2016-09-16 1:36 ` Shawn Guo
2016-09-16 14:33 ` Fabio Estevam
2016-09-16 14:42 ` Philipp Zabel
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