[v1,3/8] soc: mediatek: mtk-mmsys: Add compile time check for mmsys routes

Commit Message

AngeloGioacchino Del Regno Feb. 12, 2025, 10 a.m. UTC

Every MediaTek SoC with multimedia capabilities has an array of
structure mtk_mmsys_routes that defines a multimedia connection
between hardware components.

This connection is activated by writing a (masked) value in each
specific register, and the association between from->to path and
value to write is expressed as an entry in that array.

Failing to set the right path does not give any meaningful error
and makes things to simply not work as the data will either not
be retrieved from the right input port, or will be written to
the wrong output port (or both): since a misconfiguration may
effectively still be a possibly correct configuration at the HW
level, this may be only giving side effects in terms of simply
getting no functionality but, again, no errors.

In order to reduce room for mistakes in declarations of the
mmsys routes, add a macro that compile-time checks that the
provided value does at least fit in the register mask.

Signed-off-by: AngeloGioacchino Del Regno <[e-mail]>
---
 drivers/soc/mediatek/mtk-mmsys.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

Patch

diff --git a/drivers/soc/mediatek/mtk-mmsys.h b/drivers/soc/mediatek/mtk-mmsys.h
index d370192737ca..d5f6fbdc6f72 100644
--- a/drivers/soc/mediatek/mtk-mmsys.h
+++ b/drivers/soc/mediatek/mtk-mmsys.h
@@ -80,6 +80,20 @@ 
 
 #define MMSYS_RST_NR(bank, bit) (((bank) * 32) + (bit))
 
+/*
+ * This macro adds a compile time check to make sure that the in/out
+ * selection bit(s) fit in the register mask, similar to bitfield
+ * macros, but this does not transform the value.
+ */
+#define MMSYS_ROUTE(from, to, reg_addr, reg_mask, selection)		\
+	{ DDP_COMPONENT_##from, DDP_COMPONENT_##to, reg_addr, reg_mask,	\
+	  (__BUILD_BUG_ON_ZERO_MSG((reg_mask) == 0, "Invalid mask") +	\
+	   __BUILD_BUG_ON_ZERO_MSG(~(reg_mask) & (selection),		\
+				   #selection " does not fit in "	\
+				   #reg_mask) +				\
+	   (selection))							\
+	}
+
 struct mtk_mmsys_routes {
 	u32 from_comp;
 	u32 to_comp;