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Commit 5d283b08 authored by Fabio Estevam's avatar Fabio Estevam Committed by Shawn Guo
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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: default avatarRanjani Vaidyanathan <Ranjani.Vaidyanathan@nxp.com>
Signed-off-by: default avatarFabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: default avatarPhilipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: default avatarAkshay Bhat <akshay.bhat@timesys.com>
Tested-by Joshua Clayton <stillcompiling@gmail.com>
Tested-by: default avatarCharles Kang <Charles.Kang@advantech.com.tw>
Signed-off-by: default avatarShawn Guo <shawnguo@kernel.org>
parent 03d576f2

drivers/clk/imx/clk-imx6q.c

+259 −5
Original line number Diff line number Diff line
@@ -156,9 +156,90 @@ static struct clk ** const uart_clks[] __initconst = { 
	NULL

};



static int ldb_di_sel_by_clock_id(int clock_id)

{

	switch (clock_id) {

	case IMX6QDL_CLK_PLL5_VIDEO_DIV:

		if (clk_on_imx6q() &&

		    imx_get_soc_revision() == IMX_CHIP_REVISION_1_0)

			return -ENOENT;

		return 0;

	case IMX6QDL_CLK_PLL2_PFD0_352M:

		return 1;

	case IMX6QDL_CLK_PLL2_PFD2_396M:

		return 2;

	case IMX6QDL_CLK_MMDC_CH1_AXI:

		return 3;

	case IMX6QDL_CLK_PLL3_USB_OTG:

		return 4;

	default:

		return -ENOENT;

	}

}



static void of_assigned_ldb_sels(struct device_node *node,

				 unsigned int *ldb_di0_sel,

				 unsigned int *ldb_di1_sel)

{

	struct of_phandle_args clkspec;

	int index, rc, num_parents;

	int parent, child, sel;



	num_parents = of_count_phandle_with_args(node, "assigned-clock-parents",

						 "#clock-cells");

	for (index = 0; index < num_parents; index++) {

		rc = of_parse_phandle_with_args(node, "assigned-clock-parents",

					"#clock-cells", index, &clkspec);

		if (rc < 0) {

			/* skip empty (null) phandles */

			if (rc == -ENOENT)

				continue;

			else

				return;

		}

		if (clkspec.np != node || clkspec.args[0] >= IMX6QDL_CLK_END) {

			pr_err("ccm: parent clock %d not in ccm\n", index);

			return;

		}

		parent = clkspec.args[0];



		rc = of_parse_phandle_with_args(node, "assigned-clocks",

				"#clock-cells", index, &clkspec);

		if (rc < 0)

			return;

		if (clkspec.np != node || clkspec.args[0] >= IMX6QDL_CLK_END) {

			pr_err("ccm: child clock %d not in ccm\n", index);

			return;

		}

		child = clkspec.args[0];



		if (child != IMX6QDL_CLK_LDB_DI0_SEL &&

		    child != IMX6QDL_CLK_LDB_DI1_SEL)

			continue;



		sel = ldb_di_sel_by_clock_id(parent);

		if (sel < 0) {

			pr_err("ccm: invalid ldb_di%d parent clock: %d\n",

			       child == IMX6QDL_CLK_LDB_DI1_SEL, parent);

			continue;

		}



		if (child == IMX6QDL_CLK_LDB_DI0_SEL)

			*ldb_di0_sel = sel;

		if (child == IMX6QDL_CLK_LDB_DI1_SEL)

			*ldb_di1_sel = sel;

	}

}



#define CCM_CCDR		0x04

#define CCM_CCSR		0x0c

#define CCM_CS2CDR		0x2c



#define CCDR_MMDC_CH1_MASK		BIT(16)

#define CCSR_PLL3_SW_CLK_SEL		BIT(0)



#define CS2CDR_LDB_DI0_CLK_SEL_SHIFT	9

#define CS2CDR_LDB_DI1_CLK_SEL_SHIFT	12



static void __init imx6q_mmdc_ch1_mask_handshake(void __iomem *ccm_base)

{
@@ -169,10 +250,173 @@ static void __init imx6q_mmdc_ch1_mask_handshake(void __iomem *ccm_base) 
	writel_relaxed(reg, ccm_base + CCM_CCDR);

}



/*

 * The only way to disable the MMDC_CH1 clock is to move it to pll3_sw_clk

 * via periph2_clk2_sel and then to disable pll3_sw_clk by selecting the

 * bypass clock source, since there is no CG bit for mmdc_ch1.

 */

static void mmdc_ch1_disable(void __iomem *ccm_base)

{

	unsigned int reg;



	clk_set_parent(clk[IMX6QDL_CLK_PERIPH2_CLK2_SEL],

		       clk[IMX6QDL_CLK_PLL3_USB_OTG]);



	/*

	 * Handshake with mmdc_ch1 module must be masked when changing

	 * periph2_clk_sel.

	 */

	clk_set_parent(clk[IMX6QDL_CLK_PERIPH2], clk[IMX6QDL_CLK_PERIPH2_CLK2]);



	/* Disable pll3_sw_clk by selecting the bypass clock source */

	reg = readl_relaxed(ccm_base + CCM_CCSR);

	reg |= CCSR_PLL3_SW_CLK_SEL;

	writel_relaxed(reg, ccm_base + CCM_CCSR);

}



static void mmdc_ch1_reenable(void __iomem *ccm_base)

{

	unsigned int reg;



	/* Enable pll3_sw_clk by disabling the bypass */

	reg = readl_relaxed(ccm_base + CCM_CCSR);

	reg &= ~CCSR_PLL3_SW_CLK_SEL;

	writel_relaxed(reg, ccm_base + CCM_CCSR);



	clk_set_parent(clk[IMX6QDL_CLK_PERIPH2], clk[IMX6QDL_CLK_PERIPH2_PRE]);

}



/*

 * We have to follow a strict procedure when changing the LDB clock source,

 * otherwise we risk introducing a glitch that can lock up the LDB divider.

 * Things to keep in mind:

 *

 * 1. The current and new parent clock inputs to the mux must be disabled.

 * 2. The default clock input for ldb_di0/1_clk_sel is mmdc_ch1_axi, which

 *    has no CG bit.

 * 3. pll2_pfd2_396m can not be gated if it is used as memory clock.

 * 4. In the RTL implementation of the LDB_DI_CLK_SEL muxes the top four

 *    options are in one mux and the PLL3 option along with three unused

 *    inputs is in a second mux. There is a third mux with two inputs used

 *    to decide between the first and second 4-port mux:

 *

 *    pll5_video_div 0 --|\

 *    pll2_pfd0_352m 1 --| |_

 *    pll2_pfd2_396m 2 --| | `-|\

 *    mmdc_ch1_axi   3 --|/    | |

 *                             | |--

 *    pll3_usb_otg   4 --|\    | |

 *                   5 --| |_,-|/

 *                   6 --| |

 *                   7 --|/

 *

 * The ldb_di0/1_clk_sel[1:0] bits control both 4-port muxes at the same time.

 * The ldb_di0/1_clk_sel[2] bit controls the 2-port mux. The code below

 * switches the parent to the bottom mux first and then manipulates the top

 * mux to ensure that no glitch will enter the divider.

 */

static void init_ldb_clks(struct device_node *np, void __iomem *ccm_base)

{

	unsigned int reg;

	unsigned int sel[2][4];

	int i;



	reg = readl_relaxed(ccm_base + CCM_CS2CDR);

	sel[0][0] = (reg >> CS2CDR_LDB_DI0_CLK_SEL_SHIFT) & 7;

	sel[1][0] = (reg >> CS2CDR_LDB_DI1_CLK_SEL_SHIFT) & 7;



	sel[0][3] = sel[0][2] = sel[0][1] = sel[0][0];

	sel[1][3] = sel[1][2] = sel[1][1] = sel[1][0];



	of_assigned_ldb_sels(np, &sel[0][3], &sel[1][3]);



	for (i = 0; i < 2; i++) {

		/* Warn if a glitch might have been introduced already */

		if (sel[i][0] != 3) {

			pr_warn("ccm: ldb_di%d_sel already changed from reset value: %d\n",

				i, sel[i][0]);

		}



		if (sel[i][0] == sel[i][3])

			continue;



		/* Only switch to or from pll2_pfd2_396m if it is disabled */

		if ((sel[i][0] == 2 || sel[i][3] == 2) &&

		    (clk_get_parent(clk[IMX6QDL_CLK_PERIPH_PRE]) ==

		     clk[IMX6QDL_CLK_PLL2_PFD2_396M])) {

			pr_err("ccm: ldb_di%d_sel: couldn't disable pll2_pfd2_396m\n",

			       i);

			sel[i][3] = sel[i][2] = sel[i][1] = sel[i][0];

			continue;

		}



		/* First switch to the bottom mux */

		sel[i][1] = sel[i][0] | 4;



		/* Then configure the top mux before switching back to it */

		sel[i][2] = sel[i][3] | 4;



		pr_debug("ccm: switching ldb_di%d_sel: %d->%d->%d->%d\n", i,

			 sel[i][0], sel[i][1], sel[i][2], sel[i][3]);

	}



	if (sel[0][0] == sel[0][3] && sel[1][0] == sel[1][3])

		return;



	mmdc_ch1_disable(ccm_base);



	for (i = 1; i < 4; i++) {

		reg = readl_relaxed(ccm_base + CCM_CS2CDR);

		reg &= ~((7 << CS2CDR_LDB_DI0_CLK_SEL_SHIFT) |

			 (7 << CS2CDR_LDB_DI1_CLK_SEL_SHIFT));

		reg |= ((sel[0][i] << CS2CDR_LDB_DI0_CLK_SEL_SHIFT) |

			(sel[1][i] << CS2CDR_LDB_DI1_CLK_SEL_SHIFT));

		writel_relaxed(reg, ccm_base + CCM_CS2CDR);

	}



	mmdc_ch1_reenable(ccm_base);

}



#define CCM_ANALOG_PLL_VIDEO	0xa0

#define CCM_ANALOG_PFD_480	0xf0

#define CCM_ANALOG_PFD_528	0x100



#define PLL_ENABLE		BIT(13)



#define PFD0_CLKGATE		BIT(7)

#define PFD1_CLKGATE		BIT(15)

#define PFD2_CLKGATE		BIT(23)

#define PFD3_CLKGATE		BIT(31)



static void disable_anatop_clocks(void __iomem *anatop_base)

{

	unsigned int reg;



	/* Make sure PLL2 PFDs 0-2 are gated */

	reg = readl_relaxed(anatop_base + CCM_ANALOG_PFD_528);

	/* Cannot gate PFD2 if pll2_pfd2_396m is the parent of MMDC clock */

	if (clk_get_parent(clk[IMX6QDL_CLK_PERIPH_PRE]) ==

	    clk[IMX6QDL_CLK_PLL2_PFD2_396M])

		reg |= PFD0_CLKGATE | PFD1_CLKGATE;

	else

		reg |= PFD0_CLKGATE | PFD1_CLKGATE | PFD2_CLKGATE;

	writel_relaxed(reg, anatop_base + CCM_ANALOG_PFD_528);



	/* Make sure PLL3 PFDs 0-3 are gated */

	reg = readl_relaxed(anatop_base + CCM_ANALOG_PFD_480);

	reg |= PFD0_CLKGATE | PFD1_CLKGATE | PFD2_CLKGATE | PFD3_CLKGATE;

	writel_relaxed(reg, anatop_base + CCM_ANALOG_PFD_480);



	/* Make sure PLL5 is disabled */

	reg = readl_relaxed(anatop_base + CCM_ANALOG_PLL_VIDEO);

	reg &= ~PLL_ENABLE;

	writel_relaxed(reg, anatop_base + CCM_ANALOG_PLL_VIDEO);

}



static void __init imx6q_clocks_init(struct device_node *ccm_node)

{

	struct device_node *np;

	void __iomem *base;

	void __iomem *anatop_base, *base;

	int i;

	int ret;
@@ -185,7 +429,7 @@ static void __init imx6q_clocks_init(struct device_node *ccm_node) 
	clk[IMX6QDL_CLK_ANACLK2] = imx_obtain_fixed_clock("anaclk2", 0);



	np = of_find_compatible_node(NULL, NULL, "fsl,imx6q-anatop");

	base = of_iomap(np, 0);

	anatop_base = base = of_iomap(np, 0);

	WARN_ON(!base);



	/* Audio/video PLL post dividers do not work on i.MX6q revision 1.0 */
@@ -310,8 +554,6 @@ static void __init imx6q_clocks_init(struct device_node *ccm_node) 
	base = of_iomap(np, 0);

	WARN_ON(!base);



	imx6q_mmdc_ch1_mask_handshake(base);



	/*                                              name                reg       shift width parent_names     num_parents */

	clk[IMX6QDL_CLK_STEP]             = imx_clk_mux("step",	            base + 0xc,  8,  1, step_sels,	   ARRAY_SIZE(step_sels));

	clk[IMX6QDL_CLK_PLL1_SW]          = imx_clk_mux("pll1_sw",	    base + 0xc,  2,  1, pll1_sw_sels,      ARRAY_SIZE(pll1_sw_sels));
@@ -345,6 +587,18 @@ static void __init imx6q_clocks_init(struct device_node *ccm_node) 
		clk[IMX6QDL_CLK_GPU3D_SHADER_SEL] = imx_clk_mux("gpu3d_shader_sel", base + 0x18, 8,  2, gpu3d_shader_sels, ARRAY_SIZE(gpu3d_shader_sels));

	clk[IMX6QDL_CLK_IPU1_SEL]         = imx_clk_mux("ipu1_sel",         base + 0x3c, 9,  2, ipu_sels,          ARRAY_SIZE(ipu_sels));

	clk[IMX6QDL_CLK_IPU2_SEL]         = imx_clk_mux("ipu2_sel",         base + 0x3c, 14, 2, ipu_sels,          ARRAY_SIZE(ipu_sels));



	disable_anatop_clocks(anatop_base);



	imx6q_mmdc_ch1_mask_handshake(base);



	/*

	 * The LDB_DI0/1_SEL muxes are registered read-only due to a hardware

	 * bug. Set the muxes to the requested values before registering the

	 * ldb_di_sel clocks.

	 */

	init_ldb_clks(np, base);



	clk[IMX6QDL_CLK_LDB_DI0_SEL]      = imx_clk_mux_ldb("ldb_di0_sel", base + 0x2c, 9,  3, ldb_di_sels,      ARRAY_SIZE(ldb_di_sels));

	clk[IMX6QDL_CLK_LDB_DI1_SEL]      = imx_clk_mux_ldb("ldb_di1_sel", base + 0x2c, 12, 3, ldb_di_sels,      ARRAY_SIZE(ldb_di_sels));

	clk[IMX6QDL_CLK_IPU1_DI0_PRE_SEL] = imx_clk_mux_flags("ipu1_di0_pre_sel", base + 0x34, 6,  3, ipu_di_pre_sels,   ARRAY_SIZE(ipu_di_pre_sels), CLK_SET_RATE_PARENT);