[PATCH 3/3] clk: imx6q: handle ENET PLL bypass
From: stefan@agner.ch (Stefan Agner)
Date: 2018-08-10 07:45:54
Also in:
linux-clk, linux-devicetree
On 31.07.2018 12:20, Lucas Stach wrote:
The ENET PLL is different from the other i.MX6 PLLs, as it has
multiple outputs with different post-dividers, which are all
bypassed if the single bypass bit is activated. The hardware setup
looks something like this:
_
refclk-o---PLL---o----DIV1-----| \
| | |M |----OUT1
o-----------------------|_/
| | _
| o----DIV2-----| \
| | |M |----OUT2
o-----------------------|_/
| | _
| `----DIV3-----| \
| |M |----OUT3
`-----------------------|_/
The bypass bit not only bypasses the PLL, but also the attached
post-dividers. This would be reasonbly straight forward to model
with a single output, or with different bypass bits for each output,
but sadly the HW guys decided that it would be good to actuate all
3 muxes with a single bit.So that bypass bit is set when using IMX6QDL_PLL6_BYPASS_SRC correct? So what happens today when one is doing that? Clocks such as IMX6QDL_CLK_ENET_REF get the clock rate wrong?
So the need to have the PLL bypassed for one of the outputs always affects 2 other (in our model) independent branches of the clock tree. This means the decision to bypass this PLL is a system wide design choice and should not be changed on-the-fly, so we can treat any bapass configuration as static. As such we can just register the
s/bapass/bypass
post-dividiers with a ratio that reflects the bypass status, which allows us to bypass the PLL without breaking our abstraction model and with it DT stability.
I am assuming that the bypass bit is set depending on device tree parent setting. So you basically parse the device tree again to infer what the code did a bit further up? Can we not just read the bit from hardware? We already access clock registers directly why not this one... -- Stefan
quoted hunk ↗ jump to hunk
Signed-off-by: Lucas Stach <l.stach@pengutronix.de> --- drivers/clk/imx/clk-imx6q.c | 63 +++++++++++++++++++++++++++++++++---- 1 file changed, 57 insertions(+), 6 deletions(-)diff --git a/drivers/clk/imx/clk-imx6q.c b/drivers/clk/imx/clk-imx6q.c index f64f0fe76658..c52294694273 100644 --- a/drivers/clk/imx/clk-imx6q.c +++ b/drivers/clk/imx/clk-imx6q.c@@ -231,6 +231,41 @@ static void of_assigned_ldb_sels(struct device_node *node, } } +static bool pll6_bypassed(struct device_node *node) +{ + int index, ret, num_clocks; + struct of_phandle_args clkspec; + + num_clocks = of_count_phandle_with_args(node, "assigned-clocks", + "#clock-cells"); + if (num_clocks < 0) + return false; + + for (index = 0; index < num_clocks; index++) { + ret = of_parse_phandle_with_args(node, "assigned-clocks", + "#clock-cells", index, + &clkspec); + if (ret < 0) + return false; + + if (clkspec.np == node && + clkspec.args[0] == IMX6QDL_PLL6_BYPASS) + break; + } + + /* PLL6 bypass is not part of the assigned clock list */ + if (index == num_clocks) + return false; + + ret = of_parse_phandle_with_args(node, "assigned-clock-parents", + "#clock-cells", index, &clkspec); + + if (clkspec.args[0] != IMX6QDL_CLK_PLL6) + return true; + + return false; +} + #define CCM_CCDR 0x04 #define CCM_CCSR 0x0c #define CCM_CS2CDR 0x2c@@ -510,16 +545,32 @@ static void __init imx6q_clocks_init(structdevice_node *ccm_node) clk[IMX6QDL_CLK_USBPHY1_GATE] = imx_clk_gate("usbphy1_gate", "dummy", base + 0x10, 6); clk[IMX6QDL_CLK_USBPHY2_GATE] = imx_clk_gate("usbphy2_gate", "dummy", base + 0x20, 6); - clk[IMX6QDL_CLK_SATA_REF] = imx_clk_fixed_factor("sata_ref", "pll6_enet", 1, 5); - clk[IMX6QDL_CLK_PCIE_REF] = imx_clk_fixed_factor("pcie_ref", "pll6_enet", 1, 4); + /* + * The ENET PLL is special in that is has multiple outputs with + * different post-dividers that are all affected by the single bypass + * bit, so a single mux bit affects 3 independent branches of the clock + * tree. There is no good way to model this in the clock framework and + * dynamically changing the bypass bit, will yield unexpected results. + * So we treat any configuration that bypasses the ENET PLL as + * essentially static with the divider ratios refelcting the bypass + * status. + * + */ + if (!pll6_bypassed(ccm_node)) { + clk[IMX6QDL_CLK_SATA_REF] = imx_clk_fixed_factor("sata_ref", "pll6_enet", 1, 5); + clk[IMX6QDL_CLK_PCIE_REF] = imx_clk_fixed_factor("pcie_ref", "pll6_enet", 1, 4); + clk[IMX6QDL_CLK_ENET_REF] = clk_register_divider_table(NULL, "enet_ref", "pll6_enet", 0, + base + 0xe0, 0, 2, 0, clk_enet_ref_table, + &imx_ccm_lock); + } else { + clk[IMX6QDL_CLK_SATA_REF] = imx_clk_fixed_factor("sata_ref", "pll6_enet", 1, 1); + clk[IMX6QDL_CLK_PCIE_REF] = imx_clk_fixed_factor("pcie_ref", "pll6_enet", 1, 1); + clk[IMX6QDL_CLK_ENET_REF] = imx_clk_fixed_factor("enet_ref", "pll6_enet", 1, 1); + } clk[IMX6QDL_CLK_SATA_REF_100M] = imx_clk_gate("sata_ref_100m", "sata_ref", base + 0xe0, 20); clk[IMX6QDL_CLK_PCIE_REF_125M] = imx_clk_gate("pcie_ref_125m", "pcie_ref", base + 0xe0, 19); - clk[IMX6QDL_CLK_ENET_REF] = clk_register_divider_table(NULL, "enet_ref", "pll6_enet", 0, - base + 0xe0, 0, 2, 0, clk_enet_ref_table, - &imx_ccm_lock); - clk[IMX6QDL_CLK_LVDS1_SEL] = imx_clk_mux("lvds1_sel", base + 0x160, 0, 5, lvds_sels, ARRAY_SIZE(lvds_sels)); clk[IMX6QDL_CLK_LVDS2_SEL] = imx_clk_mux("lvds2_sel", base + 0x160, 5, 5, lvds_sels, ARRAY_SIZE(lvds_sels));