On Tue, Dec 5, 2023 at 4:31 AM Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:
6.1-stable review patch. If anyone has any objections, please let me know.
From: Hugo Villeneuve hvilleneuve@dimonoff.com
commit 35b464e32c8bccef435e415db955787ead4ab44c upstream.
The DISPLAY_CLEAR command on the NewHaven NHD-0220DZW-AG5 display does NOT change the DDRAM address to 00h (home position) like the standard Hitachi HD44780 controller. As a consequence, the starting position of the initial string LCD_INIT_TEXT is not guaranteed to be at 0,0 depending on where the cursor was before the DISPLAY_CLEAR command.
Extract of DISPLAY_CLEAR command from datasheets of:
Hitachi HD44780: ... It then sets DDRAM address 0 into the address counter... NewHaven NHD-0220DZW-AG5 datasheet: ... This instruction does not change the DDRAM AddressMove the cursor home after sending DISPLAY_CLEAR command to support non-standard LCDs.
Signed-off-by: Hugo Villeneuve hvilleneuve@dimonoff.com Reviewed-by: Geert Uytterhoeven geert@linux-m68k.org Tested-by: David Reaver me@davidreaver.com Link: https://lore.kernel.org/r/20230722180925.1408885-1-hugo@hugovil.com Signed-off-by: Miguel Ojeda ojeda@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
The commit enables more hardware to work, so it is a "feature" in sense. It does not break the current supported hardware (as far as we know -- David's `Tested-by` was on HD44780), but as usual, there is always a risk with any change.
If it is OK to take commits like this into stable or somebody wanted to use that hardware in 6.1, then I assume it is fine, but I wanted to point it out just in case.
Thanks!
Cheers, Miguel