From 48d7f160b10711f014bf07b574c73452646c9fdd Mon Sep 17 00:00:00 2001 From: Stephen Boyd Date: Mon, 5 Nov 2018 11:40:10 -0800 Subject: [PATCH 1/2] dt-bindings: clk: Introduce 'protected-clocks' property Add a generic clk property for clks which are not intended to be used by the OS due to security restrictions put in place by firmware. For example, on some Qualcomm firmwares reading or writing certain clk registers causes the entire system to reboot, but on other firmwares reading and writing those same registers is required to make devices like QSPI work. Rather than adding one-off properties each time a new set of clks appears to be protected, let's add a generic clk property to describe any set of clks that shouldn't be touched by the OS. This way we never need to register the clks or use them in certain firmware configurations. Cc: Rob Herring Cc: Bjorn Andersson Cc: Taniya Das Signed-off-by: Stephen Boyd Reviewed-by: Bjorn Andersson Reviewed-by: Rob Herring Signed-off-by: Stephen Boyd --- .../devicetree/bindings/clock/clock-bindings.txt | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/Documentation/devicetree/bindings/clock/clock-bindings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt index 2ec489eebe72..b646bbcf7f92 100644 --- a/Documentation/devicetree/bindings/clock/clock-bindings.txt +++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt @@ -168,3 +168,19 @@ a shared clock is forbidden. Configuration of common clocks, which affect multiple consumer devices can be similarly specified in the clock provider node. + +==Protected clocks== + +Some platforms or firmwares may not fully expose all the clocks to the OS, such +as in situations where those clks are used by drivers running in ARM secure +execution levels. Such a configuration can be specified in device tree with the +protected-clocks property in the form of a clock specifier list. This property should +only be specified in the node that is providing the clocks being protected: + + clock-controller@a000f000 { + compatible = "vendor,clk95; + reg = <0xa000f000 0x1000> + #clocks-cells = <1>; + ... + protected-clocks = , ; + }; From b181b3b801da8893c8eb706e448dd5111b02de60 Mon Sep 17 00:00:00 2001 From: Stephen Boyd Date: Mon, 5 Nov 2018 11:40:11 -0800 Subject: [PATCH 2/2] clk: qcom: Support 'protected-clocks' property Certain firmware configurations "protect" clks and cause the entire system to reboot when a non-secure OS such as Linux tries to read or write protected clk registers. But other firmware configurations allow reading or writing the same registers, and they may actually require that the OS use the otherwise locked down clks. Support the 'protected-clocks' property by never registering these protected clks with the common clk framework. This way, when firmware is protecting these clks we won't have the chance to ever read or write these registers and take down the entire system. Cc: Taniya Das Cc: Bjorn Andersson Signed-off-by: Stephen Boyd Reviewed-by: Bjorn Andersson Signed-off-by: Stephen Boyd --- drivers/clk/qcom/common.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/drivers/clk/qcom/common.c b/drivers/clk/qcom/common.c index db9b2471ac40..0a48ed56833b 100644 --- a/drivers/clk/qcom/common.c +++ b/drivers/clk/qcom/common.c @@ -191,6 +191,22 @@ int qcom_cc_register_sleep_clk(struct device *dev) } EXPORT_SYMBOL_GPL(qcom_cc_register_sleep_clk); +/* Drop 'protected-clocks' from the list of clocks to register */ +static void qcom_cc_drop_protected(struct device *dev, struct qcom_cc *cc) +{ + struct device_node *np = dev->of_node; + struct property *prop; + const __be32 *p; + u32 i; + + of_property_for_each_u32(np, "protected-clocks", prop, p, i) { + if (i >= cc->num_rclks) + continue; + + cc->rclks[i] = NULL; + } +} + static struct clk_hw *qcom_cc_clk_hw_get(struct of_phandle_args *clkspec, void *data) { @@ -251,6 +267,8 @@ int qcom_cc_really_probe(struct platform_device *pdev, cc->rclks = rclks; cc->num_rclks = num_clks; + qcom_cc_drop_protected(dev, cc); + for (i = 0; i < num_clks; i++) { if (!rclks[i]) continue;