Re: [PATCH v3 4/6] clk: imx6: Make the LDB_DI0 and LDB_DI1 clocks read-only

[Roland Hieber <rhi@pengutronix.de>]

On Wed, Jul 17, 2019 at 07:06:02PM +0200, Ahmad Fatoum wrote:
> From: Philipp Zabel <p.zabel@pengutronix.de>
> 
> 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. As this can not be guaranteed by
> the clock framework during runtime, make the ldb_di[x]_sel muxes read-only.
> A workaround to set the muxes once during boot could be added to the
> kernel or bootloader.
> 
> Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
> Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
> Signed-off-by: Shawn Guo <shawnguo@kernel.org>
> [afa: reviewed for barebox]
> Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
> Tested-by: Andrey Smirnov <andrew.smirnov@gmail.com>
> [afa: ported from Linux kernel commit 03d576f202]

Should this line be further above, or were the lines above all part of
the Linux commit?

 - Roland

> [afa: added exception for i.MX6QP, see kernel commit f4a0a6c309]
> [afa: added cpu_has_err009219 helper function]
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> ---
>  drivers/clk/imx/clk-imx6.c | 17 +++++++++++++++--
>  drivers/clk/imx/clk.h      |  8 ++++++++
>  2 files changed, 23 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/clk/imx/clk-imx6.c b/drivers/clk/imx/clk-imx6.c
> index 6f19535be7ba..61819ff9744d 100644
> --- a/drivers/clk/imx/clk-imx6.c
> +++ b/drivers/clk/imx/clk-imx6.c
> @@ -64,6 +64,13 @@ static inline int cpu_mx6_is_plus(void)
>  	return cpu_mx6_is_mx6qp() || cpu_mx6_is_mx6dp();
>  }
>  
> +/* i.MX6 Quad/Dual/DualLite/Solo are all affected */
> +static inline int cpu_mx6_has_err009219(void)
> +{
> +	return cpu_mx6_is_mx6d() || cpu_mx6_is_mx6q() ||
> +		cpu_mx6_is_mx6dl() || cpu_mx6_is_mx6s();
> +}
> +
>  static const char *step_sels[] = {
>  	"osc",
>  	"pll2_pfd2_396m",
> @@ -316,8 +323,14 @@ static void imx6_add_video_clks(void __iomem *anab, void __iomem *cb)
>  
>  	imx6q_mmdc_ch1_mask_handshake(cb);
>  
> -	clks[IMX6QDL_CLK_LDB_DI0_SEL]      = imx_clk_mux_p("ldb_di0_sel",      cb + 0x2c, 9,  3, ldb_di_sels,       ARRAY_SIZE(ldb_di_sels));
> -	clks[IMX6QDL_CLK_LDB_DI1_SEL]      = imx_clk_mux_p("ldb_di1_sel",      cb + 0x2c, 12, 3, ldb_di_sels,       ARRAY_SIZE(ldb_di_sels));
> +	if (cpu_mx6_has_err009219()) {
> +		clks[IMX6QDL_CLK_LDB_DI0_SEL] = imx_clk_mux_ldb("ldb_di0_sel",    cb + 0x2c, 9,  3, ldb_di_sels,      ARRAY_SIZE(ldb_di_sels));
> +		clks[IMX6QDL_CLK_LDB_DI1_SEL] = imx_clk_mux_ldb("ldb_di1_sel",    cb + 0x2c, 12, 3, ldb_di_sels,       ARRAY_SIZE(ldb_di_sels));
> +	} else {
> +		clks[IMX6QDL_CLK_LDB_DI0_SEL] = imx_clk_mux_p("ldb_di0_sel",    cb + 0x2c, 9,  3, ldb_di_sels,      ARRAY_SIZE(ldb_di_sels));
> +		clks[IMX6QDL_CLK_LDB_DI1_SEL] = imx_clk_mux_p("ldb_di1_sel",    cb + 0x2c, 12, 3, ldb_di_sels,       ARRAY_SIZE(ldb_di_sels));
> +	}
> +
>  	clks[IMX6QDL_CLK_IPU1_DI0_PRE_SEL] = imx_clk_mux_p("ipu1_di0_pre_sel", cb + 0x34, 6,  3, ipu_di_pre_sels,   ARRAY_SIZE(ipu_di_pre_sels));
>  	clks[IMX6QDL_CLK_IPU1_DI1_PRE_SEL] = imx_clk_mux_p("ipu1_di1_pre_sel", cb + 0x34, 15, 3, ipu_di_pre_sels,   ARRAY_SIZE(ipu_di_pre_sels));
>  	clks[IMX6QDL_CLK_IPU2_DI0_PRE_SEL] = imx_clk_mux_p("ipu2_di0_pre_sel", cb + 0x38, 6,  3, ipu_di_pre_sels,   ARRAY_SIZE(ipu_di_pre_sels));
> diff --git a/drivers/clk/imx/clk.h b/drivers/clk/imx/clk.h
> index 875c76a8b3e4..04286f03f727 100644
> --- a/drivers/clk/imx/clk.h
> +++ b/drivers/clk/imx/clk.h
> @@ -39,6 +39,14 @@ static inline struct clk *imx_clk_divider_table(const char *name,
>  				 width, table, 0);
>  }
>  
> +static inline struct clk *imx_clk_mux_ldb(const char *name, void __iomem *reg,
> +		u8 shift, u8 width, const char **parents, int num_parents)
> +{
> +	return clk_mux(name, CLK_SET_RATE_NO_REPARENT | CLK_SET_RATE_PARENT, reg,
> +		       shift, width, parents, num_parents, CLK_MUX_READ_ONLY);
> +}
> +
> +
>  static inline struct clk *imx_clk_fixed_factor(const char *name,
>  		const char *parent, unsigned int mult, unsigned int div)
>  {
> -- 
> 2.20.1
> 
> 
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-- 
Roland Hieber                     | r.hieber@pengutronix.de     |
Pengutronix e.K.                  | https://www.pengutronix.de/ |
Peiner Str. 6-8, 31137 Hildesheim | Phone: +49-5121-206917-5086 |
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