From: Heiko Stuebner heiko@sntech.de
[ Upstream commit b20150d499b3ee5c2d632fbc5ac94f98dd33accf ]
of_clk_get_hw_from_clkspec() checks all available clock-providers by comparing their of nodes to the one from the clkspec. If no matching clock provider is found, the function returns -EPROBE_DEFER to cause a re-check at a later date. If a matching clock provider is found, an authoritative answer can be retrieved from it whether the clock exists or not.
This does not take into account that the clock-provider may never appear, because it's node is disabled. This can happen when a clock is optional, provided by a separate block which never gets enabled.
One example of this happening is the rk3588's VOP, which has optional additional display clocks coming from PLLs inside the hdmiphy blocks. These can be used for better rates, but the system will also work without them.
The problem around that is described in the followups to[1]. As we already know the of node of the presumed clock provider, add a check via of_device_is_available() whether this is a "valid" device node. This prevents eternal defer loops.
Link: https://lore.kernel.org/dri-devel/20250215-vop2-hdmi1-disp-modes-v1-3-81962a... [1] Reviewed-by: Sebastian Reichel sebastian.reichel@collabora.com Tested-by: Cristian Ciocaltea cristian.ciocaltea@collabora.com Signed-off-by: Heiko Stuebner heiko@sntech.de Link: https://lore.kernel.org/r/20250222223733.2990179-1-heiko@sntech.de [sboyd@kernel.org: Reword commit text a bit] Signed-off-by: Stephen Boyd sboyd@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/clk/clk.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index 5bbd036f5295f..8474099e2cac1 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -5216,6 +5216,10 @@ of_clk_get_hw_from_clkspec(struct of_phandle_args *clkspec) if (!clkspec) return ERR_PTR(-EINVAL);
+ /* Check if node in clkspec is in disabled/fail state */ + if (!of_device_is_available(clkspec->np)) + return ERR_PTR(-ENOENT); + mutex_lock(&of_clk_mutex); list_for_each_entry(provider, &of_clk_providers, link) { if (provider->node == clkspec->np) {