This series has a bug fix for the early bootconsole as well as some related efficiency improvements and cleanup.
The relevant code is subject to CONSOLE_DEBUG, which is presently only used with CONFIG_MAC. To test this series (in qemu-system-m68k, for example) it's helpful to enable CONFIG_EARLY_PRINTK and CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER and boot with kernel parameters 'console=ttyS0 earlyprintk keep_bootcon'.
--- Changed since v1: - Solved problem with line wrap while scrolling. - Added two additional patches.
Changed since v2: - Adopted addq and subq as suggested by Andreas.
Finn Thain (3): m68k: Fix lost column on framebuffer debug console m68k: Avoid pointless recursion in debug console rendering m68k: Remove unused "cursor home" code from debug console
arch/m68k/kernel/head.S | 73 +++++++++++++++++++++-------------------- 1 file changed, 37 insertions(+), 36 deletions(-)
Move the cursor position rightward after rendering the character, not before. This avoids complications that arise when the recursive console_putc call has to wrap the line and/or scroll the display. This also fixes the linewrap bug that crops off the rightmost column.
When the cursor is at the bottom of the display, a linefeed will not move the cursor position further downward. Instead, the display scrolls upward. Avoid the repeated add/subtract sequence by way of a single subtraction at the initialization of console_struct_num_rows.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Finn Thain fthain@linux-m68k.org --- Changed since v2: - addil and subil are now addql and subql resp. --- arch/m68k/kernel/head.S | 31 +++++++++++++++++++++---------- 1 file changed, 21 insertions(+), 10 deletions(-)
diff --git a/arch/m68k/kernel/head.S b/arch/m68k/kernel/head.S index 852255cf60de..9bd8adaa756d 100644 --- a/arch/m68k/kernel/head.S +++ b/arch/m68k/kernel/head.S @@ -3400,6 +3400,7 @@ L(console_clear_loop):
movel %d4,%d1 /* screen height in pixels */ divul %a0@(FONT_DESC_HEIGHT),%d1 /* d1 = max num rows */ + subql #1,%d1 /* row range is 0 to num - 1 */
movel %d0,%a2@(Lconsole_struct_num_columns) movel %d1,%a2@(Lconsole_struct_num_rows) @@ -3546,15 +3547,14 @@ func_start console_putc,%a0/%a1/%d0-%d7 cmpib #10,%d7 jne L(console_not_lf) movel %a0@(Lconsole_struct_cur_row),%d0 - addil #1,%d0 - movel %d0,%a0@(Lconsole_struct_cur_row) movel %a0@(Lconsole_struct_num_rows),%d1 cmpl %d1,%d0 jcs 1f - subil #1,%d0 - movel %d0,%a0@(Lconsole_struct_cur_row) console_scroll + jra L(console_exit) 1: + addql #1,%d0 + movel %d0,%a0@(Lconsole_struct_cur_row) jra L(console_exit)
L(console_not_lf): @@ -3581,12 +3581,6 @@ L(console_not_cr): */ L(console_not_home): movel %a0@(Lconsole_struct_cur_column),%d0 - addql #1,%a0@(Lconsole_struct_cur_column) - movel %a0@(Lconsole_struct_num_columns),%d1 - cmpl %d1,%d0 - jcs 1f - console_putc #'\n' /* recursion is OK! */ -1: movel %a0@(Lconsole_struct_cur_row),%d1
/* @@ -3633,6 +3627,23 @@ L(console_do_font_scanline): addq #1,%d1 dbra %d7,L(console_read_char_scanline)
+ /* + * Register usage in the code below: + * a0 = pointer to console globals + * d0 = cursor column + * d1 = cursor column limit + */ + + lea %pc@(L(console_globals)),%a0 + + movel %a0@(Lconsole_struct_cur_column),%d0 + addql #1,%d0 + movel %d0,%a0@(Lconsole_struct_cur_column) /* Update cursor pos */ + movel %a0@(Lconsole_struct_num_columns),%d1 + cmpl %d1,%d0 + jcs L(console_exit) + console_putc #'\n' /* Line wrap using tail recursion */ + L(console_exit): func_return console_putc
On Thu, 27 Mar 2025 at 23:44, Finn Thain fthain@linux-m68k.org wrote:
Move the cursor position rightward after rendering the character, not before. This avoids complications that arise when the recursive console_putc call has to wrap the line and/or scroll the display. This also fixes the linewrap bug that crops off the rightmost column.
When the cursor is at the bottom of the display, a linefeed will not move the cursor position further downward. Instead, the display scrolls upward. Avoid the repeated add/subtract sequence by way of a single subtraction at the initialization of console_struct_num_rows.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Finn Thain fthain@linux-m68k.org
Changed since v2:
- addil and subil are now addql and subql resp.
Reviewed-by: Geert Uytterhoeven geert@linux-m68k.org i.e. will queue in the m68k tree for v6.17.
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
Tested-by: Stan Johnson userm57@yahoo.com
On a Mac IIci, the three patches fix the lost-column issue.
I didn't notice any regressions booting the new kernel to multiuser and accessing serial, scsi and network.
-Stan Johnson
On 3/27/25 4:39 PM, Finn Thain wrote:
This series has a bug fix for the early bootconsole as well as some related efficiency improvements and cleanup.
The relevant code is subject to CONSOLE_DEBUG, which is presently only used with CONFIG_MAC. To test this series (in qemu-system-m68k, for example) it's helpful to enable CONFIG_EARLY_PRINTK and CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER and boot with kernel parameters 'console=ttyS0 earlyprintk keep_bootcon'.
Changed since v1:
- Solved problem with line wrap while scrolling.
- Added two additional patches.
Changed since v2:
- Adopted addq and subq as suggested by Andreas.
Finn Thain (3): m68k: Fix lost column on framebuffer debug console m68k: Avoid pointless recursion in debug console rendering m68k: Remove unused "cursor home" code from debug console
arch/m68k/kernel/head.S | 73 +++++++++++++++++++++-------------------- 1 file changed, 37 insertions(+), 36 deletions(-)
linux-stable-mirror@lists.linaro.org
-
Finn Thain -
Geert Uytterhoeven -
Stan Johnson