From: Hiago De Franco hiago.franco@toradex.com
[ Upstream commit 496deecb020d14ba89ba7084fbc3024f91687023 ]
For the i.MX8X and i.MX8 family SoCs, when the Cortex-M core is powered up and started by the Cortex-A core using the bootloader (e.g., via the U-Boot bootaux command), both M-core and Linux run within the same SCFW (System Controller Firmware) partition. With that, Linux has permission to control the M-core.
But once the M-core is started by the bootloader, the SCFW automatically enables its clock and sets the clock rate. If Linux later attempts to enable the same clock via clk_prepare_enable(), the SCFW returns a 'LOCKED' error, as the clock is already configured by the SCFW. This causes the probe function in imx_rproc.c to fail, leading to the M-core power domain being shut down while the core is still running. This results in a fault from the SCU (System Controller Unit) and triggers a system reset.
To address this issue, ignore handling the clk for i.MX8X and i.MX8 M-core, as SCFW already takes care of enabling and configuring the clock.
Suggested-by: Peng Fan peng.fan@nxp.com Reviewed-by: Ulf Hansson ulf.hansson@linaro.org Reviewed-by: Peng Fan peng.fan@nxp.com Signed-off-by: Hiago De Franco hiago.franco@toradex.com Acked-by: Mathieu Poirier mathieu.poirier@linaro.org Link: https://lore.kernel.org/r/20250629172512.14857-3-hiagofranco@gmail.com Signed-off-by: Ulf Hansson ulf.hansson@linaro.org Signed-off-by: Sasha Levin sashal@kernel.org ---
LLM Generated explanations, may be completely bogus:
Based on my analysis, I can now provide a definitive answer:
**Backport Status: YES**
This commit should be backported to stable kernel trees for the following reasons:
1. **Critical bug fix preventing system reset**: The commit fixes a serious issue where the probe function failure causes the M-core power domain to be shut down while the core is still running, resulting in a fault from the SCU and triggering a system reset. This is a severe user-impacting bug that can cause unexpected system reboots.
2. **Minimal and contained change**: The fix is very simple - it just adds `|| dcfg->method == IMX_RPROC_SCU_API` to an existing condition in the `imx_rproc_clk_enable()` function. This is a one-line change that only affects the clock handling logic for i.MX8X and i.MX8 family SoCs when using SCU API method.
3. **Clear root cause**: The commit message clearly explains the issue - when the M-core is started by the bootloader, the SCFW automatically enables its clock. If Linux later attempts to enable the same clock, SCFW returns a 'LOCKED' error, causing probe failure and subsequent power domain shutdown while the core is running.
4. **No architectural changes**: This is purely a bug fix that doesn't introduce new features or change the driver architecture. It simply skips clock operations for a specific configuration where the clock is already managed by the SCFW.
5. **Platform-specific fix with no regression risk**: The change only affects i.MX8X and i.MX8 platforms using the SCU API method (`IMX_RPROC_SCU_API`). Other platforms and methods are unaffected, minimizing the risk of regression.
6. **Prevents data corruption/loss**: System resets caused by this bug could potentially lead to data loss or corruption, making this fix important for system stability.
The specific code change in `imx_rproc_clk_enable()` at line 1033 simply extends the existing check from: ```c if (dcfg->method == IMX_RPROC_NONE) ``` to: ```c if (dcfg->method == IMX_RPROC_NONE || dcfg->method == IMX_RPROC_SCU_API) ```
This ensures that for SCU-managed cores, Linux doesn't attempt to enable clocks that are already controlled by the SCFW, preventing the probe failure and subsequent system reset.
drivers/remoteproc/imx_rproc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/remoteproc/imx_rproc.c b/drivers/remoteproc/imx_rproc.c index 800015ff7ff9..cc3f5b7fe9dd 100644 --- a/drivers/remoteproc/imx_rproc.c +++ b/drivers/remoteproc/imx_rproc.c @@ -1029,8 +1029,8 @@ static int imx_rproc_clk_enable(struct imx_rproc *priv) struct device *dev = priv->dev; int ret;
- /* Remote core is not under control of Linux */ - if (dcfg->method == IMX_RPROC_NONE) + /* Remote core is not under control of Linux or it is managed by SCU API */ + if (dcfg->method == IMX_RPROC_NONE || dcfg->method == IMX_RPROC_SCU_API) return 0;
priv->clk = devm_clk_get(dev, NULL);