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clk: imx6: Mask mmdc_ch1 handshake for periph2_sel and mmdc_ch1_axi_podf

PATCH New Fabio Estevam 3 participants 8 messages Sep 16, 2016 – Oct 19, 2016

Subsystems (3)
Arm i.MX and Layerscape Common clk NXP i.MX clock drivers
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Fabio Estevam

author
#0 lore raw

PATCH 1/3 clk: imx6: Mask mmdc_ch1 handshake for periph2_sel and mmdc_ch1_axi_podf

From: Philipp Zabel <[email protected]>

MMDC CH1 is not used on i.MX6Q, so the handshake needed to change the parent of periph2_sel or the divider of mmdc_ch1_axi_podf will never succeed.
Disable the handshake mechanism to allow changing the frequency of mmdc_ch1_axi, allowing to use it as a possible source for the LDB DI clock.

Signed-off-by Philipp Zabel <[email protected]>
Signed-off-by Fabio Estevam <[email protected]>
---
 drivers/clk/imx/clk-imx6q.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)
drivers/clk/imx/clk-imx6q.c +15 -0
index ba1c1ae..dd33ebc 100644
@@ -156,6 +156,19 @@ static struct clk ** const uart_clks[] __initconst = {
 	NULL
 };
 
+#define CCM_CCDR		0x04
+
+#define CCDR_MMDC_CH1_MASK	BIT(16)
+
+static void __init imx6q_mmdc_ch1_mask_handshake(void __iomem *ccm_base)
+{
+	unsigned int reg;
+
+	reg = readl_relaxed(ccm_base + CCM_CCDR);
+	reg |= CCDR_MMDC_CH1_MASK;
+	writel_relaxed(reg, ccm_base + CCM_CCDR);
+}
+
 static void __init imx6q_clocks_init(struct device_node *ccm_node)
 {
 	struct device_node *np;

@@ -297,6 +310,8 @@ 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));
Signature · 1 line
2.7.4
author
#1 lore raw

PATCH 2/3 clk: imx6: Make the LDB_DI0 and LDB_DI1 clocks read-only

From: Philipp Zabel <[email protected]>

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 <[email protected]>
Signed-off-by Fabio Estevam <[email protected]>
---
 drivers/clk/imx/clk-imx6q.c | 10 ++--------
 drivers/clk/imx/clk.h       |  8 ++++++++
 2 files changed, 10 insertions(+), 8 deletions(-)
drivers/clk/imx/clk-imx6q.c +2 -8
index dd33ebc..9bbc994 100644
@@ -340,8 +340,8 @@ 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));
-	clk[IMX6QDL_CLK_LDB_DI0_SEL]      = imx_clk_mux_flags("ldb_di0_sel", base + 0x2c, 9,  3, ldb_di_sels,      ARRAY_SIZE(ldb_di_sels), CLK_SET_RATE_PARENT);
-	clk[IMX6QDL_CLK_LDB_DI1_SEL]      = imx_clk_mux_flags("ldb_di1_sel", base + 0x2c, 12, 3, ldb_di_sels,      ARRAY_SIZE(ldb_di_sels), CLK_SET_RATE_PARENT);
+	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);
 	clk[IMX6QDL_CLK_IPU1_DI1_PRE_SEL] = imx_clk_mux_flags("ipu1_di1_pre_sel", base + 0x34, 15, 3, ipu_di_pre_sels,   ARRAY_SIZE(ipu_di_pre_sels), CLK_SET_RATE_PARENT);
 	clk[IMX6QDL_CLK_IPU2_DI0_PRE_SEL] = imx_clk_mux_flags("ipu2_di0_pre_sel", base + 0x38, 6,  3, ipu_di_pre_sels,   ARRAY_SIZE(ipu_di_pre_sels), CLK_SET_RATE_PARENT);

@@ -593,12 +593,6 @@ static void __init imx6q_clocks_init(struct device_node *ccm_node)
 
 	clk_register_clkdev(clk[IMX6QDL_CLK_ENET_REF], "enet_ref", NULL);
 
-	if ((imx_get_soc_revision() != IMX_CHIP_REVISION_1_0) ||
-	    clk_on_imx6dl()) {
-		clk_set_parent(clk[IMX6QDL_CLK_LDB_DI0_SEL], clk[IMX6QDL_CLK_PLL5_VIDEO_DIV]);
-		clk_set_parent(clk[IMX6QDL_CLK_LDB_DI1_SEL], clk[IMX6QDL_CLK_PLL5_VIDEO_DIV]);
-	}
-
 	clk_set_rate(clk[IMX6QDL_CLK_PLL3_PFD1_540M], 540000000);
 	if (clk_on_imx6dl())
 		clk_set_parent(clk[IMX6QDL_CLK_IPU1_SEL], clk[IMX6QDL_CLK_PLL3_PFD1_540M]);
drivers/clk/imx/clk.h +8 -0
index 3799ff8..4afad3b 100644
@@ -75,6 +75,14 @@ static inline struct clk *imx_clk_fixed(const char *name, int rate)
 	return clk_register_fixed_rate(NULL, name, NULL, 0, rate);
 }
 
+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_register_mux(NULL, name, parents, num_parents,
+			CLK_SET_RATE_NO_REPARENT | CLK_SET_RATE_PARENT, reg,
+			shift, width, CLK_MUX_READ_ONLY, &imx_ccm_lock);
+}
+
 static inline struct clk *imx_clk_fixed_factor(const char *name,
 		const char *parent, unsigned int mult, unsigned int div)
 {
Signature · 1 line
2.7.4
author
#2 lore raw

PATCH 3/3 clk: imx6: Fix procedure to switch the parent of LDB_DI_CLK

In reply to Fabio Estevam

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 <[email protected]>
Signed-off-by Fabio Estevam <[email protected]>
Signed-off-by Philipp Zabel <[email protected]>
Reviewed-by Akshay Bhat <[email protected]>

Tested-by Joshua Clayton <[email protected]>

Tested-by Charles Kang <[email protected]>
Acked-by Shawn Guo <[email protected]>
---
 drivers/clk/imx/clk-imx6q.c | 264 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 259 insertions(+), 5 deletions(-)
drivers/clk/imx/clk-imx6q.c +259 -5
index 9bbc994..fc3ed87 100644
@@ -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 CCDR_MMDC_CH1_MASK	BIT(16)
+#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@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));

@@ -340,6 +582,18 @@ 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);
Signature · 1 line
2.7.4
reviewer
#3 lore raw

PATCH 3/3 clk: imx6: Fix procedure to switch the parent of LDB_DI_CLK

Hi Stephen,

Quoted 25 lines · Fabio Estevam

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

Quoted 7 lines
Signed-off-by Ranjani Vaidyanathan <[email protected]>
Signed-off-by Fabio Estevam <[email protected]>
Signed-off-by Philipp Zabel <[email protected]>
Reviewed-by Akshay Bhat <[email protected]>

Tested-by Joshua Clayton <[email protected]>

Tested-by Charles Kang <[email protected]>
Acked-by Shawn Guo <[email protected]>

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

Thanks

#4 lore raw

PATCH 3/3 clk: imx6: Fix procedure to switch the parent of LDB_DI_CLK

Quoted 36 lines · Fabio Estevam

Hi Stephen,

Quoted 25 lines · Fabio Estevam

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

Quoted 7 lines
Signed-off-by Ranjani Vaidyanathan <[email protected]>
Signed-off-by Fabio Estevam <[email protected]>
Signed-off-by Philipp Zabel <[email protected]>
Reviewed-by Akshay Bhat <[email protected]>

Tested-by Joshua Clayton <[email protected]>

Tested-by Charles Kang <[email protected]>
Acked-by Shawn Guo <[email protected]>
Quoted 3 lines

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?

Signature · 2 lines
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project
reviewer
#5 lore raw

PATCH 3/3 clk: imx6: Fix procedure to switch the parent of LDB_DI_CLK

Hi Stephen,

Quoted 9 lines · Stephen Boyd

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?

Yesterday I resent this series based on linux-next, so if you could apply them to clk-next that would be great.

Thanks

#6 lore raw

PATCH 3/3 clk: imx6: Fix procedure to switch the parent of LDB_DI_CLK

Quoted 12 lines · Fabio Estevam

Hi Stephen,

Quoted 8 lines · Stephen Boyd

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.

Quoted 5 lines
Quoted 1 line

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

Yesterday I resent this series based on linux-next, so if you could apply them to clk-next that would be great.

Ok that makes it easy. Thanks.

Signature · 2 lines
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project