[PATCH v5 3/3] clk: imx6: Fix procedure to switch the parent of LDB_DI_CLK
Philipp Zabel
p.zabel at pengutronix.de
Mon Jul 11 04:12:01 PDT 2016
From: Fabio Estevam <fabio.estevam at 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 at freescale.com>
Signed-off-by: Fabio Estevam <fabio.estevam at freescale.com>
Signed-off-by: Philipp Zabel <p.zabel at pengutronix.de>
---
Changes since v4:
- Allow to switch from PLL3 to any other parent clock
---
drivers/clk/imx/clk-imx6q.c | 264 +++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 259 insertions(+), 5 deletions(-)
diff --git a/drivers/clk/imx/clk-imx6q.c b/drivers/clk/imx/clk-imx6q.c
index 9bbc994..fc3ed87 100644
--- a/drivers/clk/imx/clk-imx6q.c
+++ b/drivers/clk/imx/clk-imx6q.c
@@ -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 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));
@@ -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);
--
2.8.1
More information about the linux-arm-kernel
mailing list