From: Jens Reidel adrian@mainlining.org
[ Upstream commit e3c13e0caa8ceb7dec1a7c4fcfd9dbef56a69fbe ]
Set CLK_OPS_PARENT_ENABLE to ensure the parent gets prepared and enabled when switching to it, fixing an "rcg didn't update its configuration" warning.
Signed-off-by: Jens Reidel adrian@mainlining.org Reviewed-by: Dmitry Baryshkov dmitry.baryshkov@oss.qualcomm.com Link: https://lore.kernel.org/r/20250919-sm7150-dispcc-fixes-v1-3-308ad47c5fce@mai... Signed-off-by: Bjorn Andersson andersson@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org ---
LLM Generated explanations, may be completely bogus:
### 3. Technical Understanding
The `CLK_OPS_PARENT_ENABLE` flag (BIT(12) in clk-provider.h) ensures that "parents need enable during gate/ungate, set rate and re-parent." Without this flag, when the pixel clock source tries to switch to a new parent clock, the parent might not be enabled, causing the RCG (Root Clock Generator) to fail to update its configuration.
This is a well-known pattern in Qualcomm clock drivers - pixel clocks dynamically switch parents during display panel initialization, and the parent must be running for the configuration switch to complete.
### 4. Scope and Risk Assessment - **Lines changed**: 1 line (adding a single flag) - **Files touched**: 1 file - **Complexity**: Very low - **Risk**: Very low - this is an established pattern used across many Qualcomm dispcc/gcc drivers
### 5. User Impact - Affects SM7150-based devices (mobile phones) - The warning indicates clock configuration issues that could affect display initialization - Limited scope - only SM7150 platform users
### 6. Stable Tree Applicability - Driver was added in **v6.11** (commit 3829c412197e1) - Only applicable to v6.11.y, v6.12.y, and newer stable trees - NOT applicable to LTS kernels: 6.6.y, 6.1.y, 5.15.y (driver doesn't exist)
### 7. Key Observations
**Against backporting:** 1. **No "Cc: stable@vger.kernel.org" tag** - The maintainers did not request stable backport 2. **No "Fixes:" tag** - Doesn't reference the original commit where the bug was introduced 3. **Very new driver** - SM7150 dispcc was added in v6.11, limiting stable applicability 4. **Not a critical issue** - A warning message, not a crash, panic, or data corruption 5. **Mobile SoC** - Users running stable kernels rarely use cutting-edge mobile phone support
**For backporting:** 1. Valid bug fix with proven pattern 2. Extremely small and low-risk change 3. Has proper review from Qualcomm clock maintainers
drivers/clk/qcom/dispcc-sm7150.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/clk/qcom/dispcc-sm7150.c b/drivers/clk/qcom/dispcc-sm7150.c index bdfff246ed3fe..ddc7230b8aea7 100644 --- a/drivers/clk/qcom/dispcc-sm7150.c +++ b/drivers/clk/qcom/dispcc-sm7150.c @@ -356,7 +356,7 @@ static struct clk_rcg2 dispcc_mdss_pclk0_clk_src = { .name = "dispcc_mdss_pclk0_clk_src", .parent_data = dispcc_parent_data_4, .num_parents = ARRAY_SIZE(dispcc_parent_data_4), - .flags = CLK_SET_RATE_PARENT, + .flags = CLK_SET_RATE_PARENT | CLK_OPS_PARENT_ENABLE, .ops = &clk_pixel_ops, }, };