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Wed, 10 Apr 2024 10:07:11 -0700 (PDT) Received: from [192.168.0.113] ([2a02:8109:aa0d:be00::4716]) by smtp.gmail.com with ESMTPSA id fw14-20020a170906c94e00b00a51def4861bsm3331881ejb.91.2024.04.10.10.07.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Apr 2024 10:07:10 -0700 (PDT) From: Caleb Connolly Date: Wed, 10 Apr 2024 19:06:58 +0200 Subject: [PATCH 2/2] clk: introduce a fallback stub driver MIME-Version: 1.0 Message-Id: <20240410-b4-stub-drivers-v1-2-6935bd2c07d1@linaro.org> References: <20240410-b4-stub-drivers-v1-0-6935bd2c07d1@linaro.org> In-Reply-To: <20240410-b4-stub-drivers-v1-0-6935bd2c07d1@linaro.org> To: Simon Glass , Tom Rini , Lukasz Majewski , Sean Anderson Cc: Heinrich Schuchardt , Ilias Apalodimas , Neil Armstrong , Sumit Garg , u-boot-qcom@groups.io, u-boot@lists.denx.de, Caleb Connolly X-Mailer: b4 0.14-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=3815; i=caleb.connolly@linaro.org; h=from:subject:message-id; bh=tBzmh2+z4vL+U5q54pC35iQjh4TVM9yOxn7t7BbRAqs=; 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If there is a dependency on a clock device which is not supported by any existing driver, and CONFIG_CLK_STUB is enabled, then the stub driver will kick in. This is intended to be useful during early bringup (e.g. if the serial port is already configured for a default rate) or for clock controllers that simply aren't vital for a platform to work. Signed-off-by: Caleb Connolly --- drivers/clk/Makefile | 1 + drivers/clk/clk-fallback.c | 39 +++++++++++++++++++++++++++++++++++++++ drivers/clk/clk-uclass.c | 4 ++++ drivers/core/Kconfig | 10 ++++++++++ 4 files changed, 54 insertions(+) diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile index 638ad04baeb0..dd57f2fd0397 100644 --- a/drivers/clk/Makefile +++ b/drivers/clk/Makefile @@ -4,8 +4,9 @@ # Wolfgang Denk, DENX Software Engineering, wd@denx.de. # obj-$(CONFIG_$(SPL_TPL_)CLK) += clk-uclass.o +obj-$(CONFIG_CLK_FALLBACK) += clk-fallback.o obj-$(CONFIG_$(SPL_TPL_)CLK) += clk_fixed_rate.o obj-$(CONFIG_$(SPL_TPL_)CLK) += clk_fixed_factor.o obj-$(CONFIG_$(SPL_TPL_)CLK_CCF) += clk.o clk-divider.o clk-mux.o clk-gate.o obj-$(CONFIG_$(SPL_TPL_)CLK_CCF) += clk-fixed-factor.o diff --git a/drivers/clk/clk-fallback.c b/drivers/clk/clk-fallback.c new file mode 100644 index 000000000000..f5733821e998 --- /dev/null +++ b/drivers/clk/clk-fallback.c @@ -0,0 +1,39 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Copyright (C) 2024 Linaro Ltd. + * + * Stub clock driver for non-vital clocks. + */ + +#include +#include +#include + +static ulong fallback_clk_set_rate(struct clk *clk, ulong rate) +{ + return (clk->rate = rate); +} + +static ulong fallback_clk_get_rate(struct clk *clk) +{ + return clk->rate; +} + +static int fallback_clk_nop(struct clk *clk) +{ + return 0; +}; + +static struct clk_ops fallback_clk_ops = { + .set_rate = fallback_clk_set_rate, + .get_rate = fallback_clk_get_rate, + .enable = fallback_clk_nop, + .disable = fallback_clk_nop, +}; + +U_BOOT_DRIVER(clk_fallback) = { + .name = "clk_fallback", + .id = UCLASS_CLK, + .ops = &fallback_clk_ops, + .flags = DM_FLAG_DEFAULT_PD_CTRL_OFF, +}; diff --git a/drivers/clk/clk-uclass.c b/drivers/clk/clk-uclass.c index ed6e60bc4841..c0cdb3cf529c 100644 --- a/drivers/clk/clk-uclass.c +++ b/drivers/clk/clk-uclass.c @@ -11,8 +11,9 @@ #include #include #include #include +#include #include #include #include #include @@ -801,6 +802,9 @@ int clk_uclass_post_probe(struct udevice *dev) UCLASS_DRIVER(clk) = { .id = UCLASS_CLK, .name = "clk", +#if CONFIG_IS_ENABLED(CLK_FALLBACK) + .fallback_drv_name = "clk_fallback", +#endif .post_probe = clk_uclass_post_probe, }; diff --git a/drivers/core/Kconfig b/drivers/core/Kconfig index 09075b9b7a15..1cf78b4303ca 100644 --- a/drivers/core/Kconfig +++ b/drivers/core/Kconfig @@ -476,5 +476,15 @@ menuconfig FALLBACK_DRIVERS driver to "stub" the resource. These stubs usually do nothing and are therefore only suitable in instances where the resource is not required. +config CLK_FALLBACK + bool "Enable the clock fallback driver" + depends on FALLBACK_DRIVERS && CLK + help + This provides a no-op clock driver that can be used as a fallback + when no other driver is available. This is useful for systems with + clock controllers that are not actually required for peripherals to + work correctly (for example the RPMh clock controller on Qualcomm + platforms). + endmenu