5.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Chen-Yu Tsai wenst@chromium.org
[ Upstream commit 79200d5851c8e7179f68a4a6f162d8f1bde4986f ]
In the previous commits that added CLK_OPS_PARENT_ENABLE, support for this flag was only added to rate change operations (rate setting and reparent) and disabling unused subtree. It was not added to the clock gate related operations. Any hardware driver that needs it for these operations will either see bogus results, or worse, hang.
This has been seen on MT8192 and MT8195, where the imp_ii2_* clk drivers set this, but dumping debugfs clk_summary would cause it to hang.
Prepare parent on prepare and enable parent on enable dependencies are already handled automatically by the core as part of its sequencing. Whether the case for "enable parent on prepare" should be supported by this flag or not is not clear, and thus ignored for now.
This change solely fixes the handling of clk_core_is_enabled, i.e. enabling the parent clock when reading the hardware state. Unfortunately clk_core_is_enabled is called in a variety of places, sometimes with the enable clock already held. To avoid deadlocking, the core will ignore readouts and just return false if CLK_OPS_PARENT_ENABLE is set but the parent isn't currently enabled.
Fixes: fc8726a2c021 ("clk: core: support clocks which requires parents enable (part 2)") Fixes: a4b3518d146f ("clk: core: support clocks which requires parents enable (part 1)") Signed-off-by: Chen-Yu Tsai wenst@chromium.org Link: https://lore.kernel.org/r/20230103092330.494102-1-wenst@chromium.org Tested-by: AngeloGioacchino Del Regno angelogioacchino.delregno@collabora.com Reviewed-by: AngeloGioacchino Del Regno angelogioacchino.delregno@collabora.com Signed-off-by: Stephen Boyd sboyd@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/clk/clk.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index b37af6b27e9c6..bf9057a8fbf06 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -251,6 +251,17 @@ static bool clk_core_is_enabled(struct clk_core *core) } }
+ /* + * This could be called with the enable lock held, or from atomic + * context. If the parent isn't enabled already, we can't do + * anything here. We can also assume this clock isn't enabled. + */ + if ((core->flags & CLK_OPS_PARENT_ENABLE) && core->parent) + if (!clk_core_is_enabled(core->parent)) { + ret = false; + goto done; + } + ret = core->ops->is_enabled(core->hw); done: if (core->rpm_enabled)