[PATCH] ns16550: Fix DM serial operation with non-DM SPL

[Andre Przywara <andre.przywara@arm.com>]

Commit 9591b63531fa ("Convert CONFIG_SYS_NS16550_MEM32 et al to Kconfig")
moved some NS16550 configuration variables into Kconfig.
Among those there is CONFIG_SYS_NS16550_REG_SIZE, which used to be only
defined for SPL build runs, but now is always set (thanks for Kconfig).
However this breaks the gating logic in ns16550.h, where we *override*
this variable for DM build, as we learn this setting from the DT instead.

As a consequence, we did the register shift twice: once when building
the register struct (as required for non-DM SPL builds), but then also
again in the driver after we parsed the reg-shift DT property.

Change the logic to match what the comment says: only observe
CONFIG_SYS_NS16550_REG_SIZE when not using DM, and ignore it otherwise.

This fixes U-Boot proper for all sunxi boards, since they are relying
on this driver being build non-DM for the SPL, but DM for U-Boot proper.

Fixes: 9591b63531fa ("Convert CONFIG_SYS_NS16550_MEM32 et al to Kconfig")
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
---
Hi,

this is admittedly a quick fix, to get sunxi booting again. This whole
code around the register access looks somewhat bonkers, to be honest,
but at the moment I don't have time to rework this.
Another possible "quicker fix" would be use a separate variable for the
register shift, so that we don't have to redefine a Kconfig variable.
Another idea would be to get rid of the struct for the registers
altogether, to remove the hacks about when to shift.

Cheers,
Andre

 include/ns16550.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/ns16550.h b/include/ns16550.h
index 243226fc3d9..e9e2aeedd16 100644
--- a/include/ns16550.h
+++ b/include/ns16550.h
@@ -26,11 +26,12 @@
 
 #include <linux/types.h>
 
-#if CONFIG_IS_ENABLED(DM_SERIAL) && !defined(CONFIG_SYS_NS16550_REG_SIZE)
+#if CONFIG_IS_ENABLED(DM_SERIAL)
 /*
  * For driver model we always use one byte per register, and sort out the
  * differences in the driver
  */
+#undef CONFIG_SYS_NS16550_REG_SIZE
 #define CONFIG_SYS_NS16550_REG_SIZE (-1)
 #endif
 
-- 
2.25.1