Fix active-low handling of MIPI CSI resets on i.MX8MQ

[PATCH 1/2] dt-bindings: reset: imx8mq: Add _N suffix to IMX8MQ_RESET_MIPI_CSI*_RESET

Posted by Robby Cai 1 day, 2 hours ago

The assert logic of the MIPI CSI reset signals is active-low on i.MX8MQ,
but the existing names do not indicate this explicitly. To improve
consistency and clarity, append the _N suffix to all
IMX8MQ_RESET_MIPI_CSI*_RESET definitions. The deprecated
IMX8MQ_RESET_MIPI_CSI*_RESET versions remain temporarily for DT ABI
compatibility and will be removed at an appropriate time in the future.

Signed-off-by: Robby Cai <robby.cai@nxp.com>
---
 include/dt-bindings/reset/imx8mq-reset.h | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/include/dt-bindings/reset/imx8mq-reset.h b/include/dt-bindings/reset/imx8mq-reset.h
index 705870693ec2..83a155dbbd4a 100644
--- a/include/dt-bindings/reset/imx8mq-reset.h
+++ b/include/dt-bindings/reset/imx8mq-reset.h
@@ -46,12 +46,18 @@
 #define IMX8MQ_RESET_PCIEPHY2_PERST		35	/* i.MX8MM/i.MX8MN does NOT support */
 #define IMX8MQ_RESET_PCIE2_CTRL_APPS_EN		36	/* i.MX8MM/i.MX8MN does NOT support */
 #define IMX8MQ_RESET_PCIE2_CTRL_APPS_TURNOFF	37	/* i.MX8MM/i.MX8MN does NOT support */
-#define IMX8MQ_RESET_MIPI_CSI1_CORE_RESET	38	/* i.MX8MM/i.MX8MN does NOT support */
-#define IMX8MQ_RESET_MIPI_CSI1_PHY_REF_RESET	39	/* i.MX8MM/i.MX8MN does NOT support */
-#define IMX8MQ_RESET_MIPI_CSI1_ESC_RESET	40	/* i.MX8MM/i.MX8MN does NOT support */
-#define IMX8MQ_RESET_MIPI_CSI2_CORE_RESET	41	/* i.MX8MM/i.MX8MN does NOT support */
-#define IMX8MQ_RESET_MIPI_CSI2_PHY_REF_RESET	42	/* i.MX8MM/i.MX8MN does NOT support */
-#define IMX8MQ_RESET_MIPI_CSI2_ESC_RESET	43	/* i.MX8MM/i.MX8MN does NOT support */
+#define IMX8MQ_RESET_MIPI_CSI1_CORE_RESET	38	/* Deprecated. Use *_RESET_N instead */
+#define IMX8MQ_RESET_MIPI_CSI1_CORE_RESET_N	38	/* i.MX8MM/i.MX8MN does NOT support */
+#define IMX8MQ_RESET_MIPI_CSI1_PHY_REF_RESET	39	/* Deprecated. Use *_RESET_N instead */
+#define IMX8MQ_RESET_MIPI_CSI1_PHY_REF_RESET_N	39	/* i.MX8MM/i.MX8MN does NOT support */
+#define IMX8MQ_RESET_MIPI_CSI1_ESC_RESET	40	/* Deprecated. Use *_RESET_N instead */
+#define IMX8MQ_RESET_MIPI_CSI1_ESC_RESET_N	40	/* i.MX8MM/i.MX8MN does NOT support */
+#define IMX8MQ_RESET_MIPI_CSI2_CORE_RESET	41	/* Deprecated. Use *_RESET_N instead */
+#define IMX8MQ_RESET_MIPI_CSI2_CORE_RESET_N	41	/* i.MX8MM/i.MX8MN does NOT support */
+#define IMX8MQ_RESET_MIPI_CSI2_PHY_REF_RESET	42	/* Deprecated. Use *_RESET_N instead */
+#define IMX8MQ_RESET_MIPI_CSI2_PHY_REF_RESET_N	42	/* i.MX8MM/i.MX8MN does NOT support */
+#define IMX8MQ_RESET_MIPI_CSI2_ESC_RESET	43	/* Deprecated. Use *_RESET_N instead */
+#define IMX8MQ_RESET_MIPI_CSI2_ESC_RESET_N	43	/* i.MX8MM/i.MX8MN does NOT support */
 #define IMX8MQ_RESET_DDRC1_PRST			44	/* i.MX8MN does NOT support */
 #define IMX8MQ_RESET_DDRC1_CORE_RESET		45	/* i.MX8MN does NOT support */
 #define IMX8MQ_RESET_DDRC1_PHY_RESET		46	/* i.MX8MN does NOT support */
-- 
2.37.1

Re: [PATCH 1/2] dt-bindings: reset: imx8mq: Add _N suffix to IMX8MQ_RESET_MIPI_CSI*_RESET

Posted by Krzysztof Kozlowski 4 hours ago

On Tue, Mar 31, 2026 at 06:13:30PM +0800, Robby Cai wrote:
> The assert logic of the MIPI CSI reset signals is active-low on i.MX8MQ,
> but the existing names do not indicate this explicitly. To improve
> consistency and clarity, append the _N suffix to all
> IMX8MQ_RESET_MIPI_CSI*_RESET definitions. The deprecated
> IMX8MQ_RESET_MIPI_CSI*_RESET versions remain temporarily for DT ABI
> compatibility and will be removed at an appropriate time in the future.
> 
> Signed-off-by: Robby Cai <robby.cai@nxp.com>
> ---
>  include/dt-bindings/reset/imx8mq-reset.h | 18 ++++++++++++------
>  1 file changed, 12 insertions(+), 6 deletions(-)
> 
> diff --git a/include/dt-bindings/reset/imx8mq-reset.h b/include/dt-bindings/reset/imx8mq-reset.h
> index 705870693ec2..83a155dbbd4a 100644
> --- a/include/dt-bindings/reset/imx8mq-reset.h
> +++ b/include/dt-bindings/reset/imx8mq-reset.h
> @@ -46,12 +46,18 @@
>  #define IMX8MQ_RESET_PCIEPHY2_PERST		35	/* i.MX8MM/i.MX8MN does NOT support */
>  #define IMX8MQ_RESET_PCIE2_CTRL_APPS_EN		36	/* i.MX8MM/i.MX8MN does NOT support */
>  #define IMX8MQ_RESET_PCIE2_CTRL_APPS_TURNOFF	37	/* i.MX8MM/i.MX8MN does NOT support */
> -#define IMX8MQ_RESET_MIPI_CSI1_CORE_RESET	38	/* i.MX8MM/i.MX8MN does NOT support */
> -#define IMX8MQ_RESET_MIPI_CSI1_PHY_REF_RESET	39	/* i.MX8MM/i.MX8MN does NOT support */
> -#define IMX8MQ_RESET_MIPI_CSI1_ESC_RESET	40	/* i.MX8MM/i.MX8MN does NOT support */
> -#define IMX8MQ_RESET_MIPI_CSI2_CORE_RESET	41	/* i.MX8MM/i.MX8MN does NOT support */
> -#define IMX8MQ_RESET_MIPI_CSI2_PHY_REF_RESET	42	/* i.MX8MM/i.MX8MN does NOT support */
> -#define IMX8MQ_RESET_MIPI_CSI2_ESC_RESET	43	/* i.MX8MM/i.MX8MN does NOT support */
> +#define IMX8MQ_RESET_MIPI_CSI1_CORE_RESET	38	/* Deprecated. Use *_RESET_N instead */
> +#define IMX8MQ_RESET_MIPI_CSI1_CORE_RESET_N	38	/* i.MX8MM/i.MX8MN does NOT support */

That's quite a churn for no need. The entire point of these values being
the binding is that it describes the ABI for SW and DTS, not your
hardware registers.

Whether signal is active low or high is kind of irrelevant. Linux uses
it exactly the same way.

Best regards,
Krzysztof

Re: [PATCH 1/2] dt-bindings: reset: imx8mq: Add _N suffix to IMX8MQ_RESET_MIPI_CSI*_RESET

Posted by Philipp Zabel 23 hours ago

On Di, 2026-03-31 at 18:13 +0800, Robby Cai wrote:
> The assert logic of the MIPI CSI reset signals is active-low on i.MX8MQ,
> but the existing names do not indicate this explicitly. To improve
> consistency and clarity, append the _N suffix to all
> IMX8MQ_RESET_MIPI_CSI*_RESET definitions. The deprecated
> IMX8MQ_RESET_MIPI_CSI*_RESET versions remain temporarily for DT ABI
> compatibility and will be removed at an appropriate time in the future.

The register description in the latest reference manual I can download,
IMX8MDQLQRM Rev. 3.1 (06/2021), still call these bits
MIPI_CSI1_CORE_RESET and so on (without _N). There is no mention of
polarity in the bitfield description. Is a documentation update
planned?

Right now I'd say this improves clarity, but reduces consistency with
existing documentation.

Are these bits self-clearing, or can the reset be asserted by writing
0? As it stands, the CSI driver using these resets, imx8mq-mipi-csi2.c,
only calls reset_control_assert() in imx8mq_mipi_csi_sw_reset():

          /*                                                          
           * these are most likely self-clearing reset bits. to make it
           * more clear, the reset-imx7 driver should implement the   
           * .reset() operation.                                      
           */                     
          ret = reset_control_assert(state->rst);

This will probably have to be turned into a deassert together with the
reset driver change.

regards
Philipp