clk: Stop forwarding clk_rate_requests to the parent

If the clock cannot modify its rate and has CLK_SET_RATE_PARENT,
clk_mux_determine_rate_flags(), clk_core_round_rate_nolock() and a
number of drivers will forward the clk_rate_request to the parent clock.

clk_core_round_rate_nolock() will pass the pointer directly, which means
that we pass a clk_rate_request to the parent that has the rate,
min_rate and max_rate of the child, and the best_parent_rate and
best_parent_hw fields will be relative to the child as well, so will
point to our current clock and its rate. The most common case for
CLK_SET_RATE_PARENT is that the child and parent clock rates will be
equal, so the rate field isn't a worry, but the other fields are.

Similarly, if the parent clock driver ever modifies the best_parent_rate
or best_parent_hw, this will be applied to the child once the call to
clk_core_round_rate_nolock() is done. best_parent_hw is probably not
going to be a valid parent, and best_parent_rate might lead to a parent
rate change different to the one that was initially computed.

clk_mux_determine_rate_flags() and the affected drivers will copy the
request before forwarding it to the parents, so they won't be affected
by the latter issue, but the former is still going to be there and will
lead to erroneous data and context being passed to the various clock
drivers in the same sub-tree.

Let's create two new functions, clk_core_forward_rate_req() and
clk_hw_forward_rate_request() for the framework and the clock providers
that will copy a request from a child clock and update the context to
match the parent's. We also update the relevant call sites in the
framework and drivers to use that new function.

Let's also add a test to make sure we avoid regressions there.

Tested-by: Alexander Stein <alexander.stein@ew.tq-group.com> # imx8mp
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com> # exynos4210, meson g12b
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20220816112530.1837489-22-maxime@cerno.tech
Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

3 files changed, 11 insertions, 7 deletions

diff --git a/drivers/clk/at91/clk-generated.c b/drivers/clk/at91/clk-generated.c
index d429ba52a719..943ea67bf135 100644
--- a/drivers/clk/at91/clk-generated.c
+++ b/drivers/clk/at91/clk-generated.c
@@ -136,7 +136,6 @@ static int clk_generated_determine_rate(struct clk_hw *hw,
 {
 	struct clk_generated *gck = to_clk_generated(hw);
 	struct clk_hw *parent = NULL;
-	struct clk_rate_request req_parent = *req;
 	long best_rate = -EINVAL;
 	unsigned long min_rate, parent_rate;
 	int best_diff = -1;
@@ -192,7 +191,9 @@ static int clk_generated_determine_rate(struct clk_hw *hw,
 		goto end;
 
 	for (div = 1; div < GENERATED_MAX_DIV + 2; div++) {
-		req_parent.rate = req->rate * div;
+		struct clk_rate_request req_parent;
+
+		clk_hw_forward_rate_request(hw, req, parent, &req_parent, req->rate * div);
 		if (__clk_determine_rate(parent, &req_parent))
 			continue;
 		clk_generated_best_diff(req, parent, req_parent.rate, div,
diff --git a/drivers/clk/at91/clk-master.c b/drivers/clk/at91/clk-master.c
index 164e2959c7cf..b7cd1924de52 100644
--- a/drivers/clk/at91/clk-master.c
+++ b/drivers/clk/at91/clk-master.c
@@ -581,7 +581,6 @@ static int clk_sama7g5_master_determine_rate(struct clk_hw *hw,
 					     struct clk_rate_request *req)
 {
 	struct clk_master *master = to_clk_master(hw);
-	struct clk_rate_request req_parent = *req;
 	struct clk_hw *parent;
 	long best_rate = LONG_MIN, best_diff = LONG_MIN;
 	unsigned long parent_rate;
@@ -618,11 +617,15 @@ static int clk_sama7g5_master_determine_rate(struct clk_hw *hw,
 		goto end;
 
 	for (div = 0; div < MASTER_PRES_MAX + 1; div++) {
+		struct clk_rate_request req_parent;
+		unsigned long req_rate;
+
 		if (div == MASTER_PRES_MAX)
-			req_parent.rate = req->rate * 3;
+			req_rate = req->rate * 3;
 		else
-			req_parent.rate = req->rate << div;
+			req_rate = req->rate << div;
 
+		clk_hw_forward_rate_request(hw, req, parent, &req_parent, req_rate);
 		if (__clk_determine_rate(parent, &req_parent))
 			continue;
 
diff --git a/drivers/clk/at91/clk-peripheral.c b/drivers/clk/at91/clk-peripheral.c
index e14fa5ac734c..5104d4025484 100644
--- a/drivers/clk/at91/clk-peripheral.c
+++ b/drivers/clk/at91/clk-peripheral.c
@@ -269,7 +269,6 @@ static int clk_sam9x5_peripheral_determine_rate(struct clk_hw *hw,
 {
 	struct clk_sam9x5_peripheral *periph = to_clk_sam9x5_peripheral(hw);
 	struct clk_hw *parent = clk_hw_get_parent(hw);
-	struct clk_rate_request req_parent = *req;
 	unsigned long parent_rate = clk_hw_get_rate(parent);
 	unsigned long tmp_rate;
 	long best_rate = LONG_MIN;
@@ -302,8 +301,9 @@ static int clk_sam9x5_peripheral_determine_rate(struct clk_hw *hw,
 		goto end;
 
 	for (shift = 0; shift <= PERIPHERAL_MAX_SHIFT; shift++) {
-		req_parent.rate = req->rate << shift;
+		struct clk_rate_request req_parent;
 
+		clk_hw_forward_rate_request(hw, req, parent, &req_parent, req->rate << shift);
 		if (__clk_determine_rate(parent, &req_parent))
 			continue;