drm/cirrus-qemu: Fix pitch programming

Do not set CR1B[6] when programming the pitch. The bit effects VGA
text mode and is not interpreted by qemu. [1] It has no affect on
the scanline pitch.

The scanline bit that is set into CR1B[6] belongs into CR13[7], which
the driver sets up correctly.

This bug goes back to the driver's initial commit.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Link: https://gitlab.com/qemu-project/qemu/-/blob/stable-9.2/hw/display/cirrus_vga.c?ref_type=heads#L1112
Fixes: f9aa76a85248 ("drm/kms: driver for virtual cirrus under qemu")
Cc: Adam Jackson <ajax@redhat.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: <stable@vger.kernel.org> # v3.5+
Link: https://lore.kernel.org/r/20250328091821.195061-2-tzimmermann@suse.de

diff --git a/drivers/gpu/drm/tiny/cirrus-qemu.c b/drivers/gpu/drm/tiny/cirrus-qemu.c
index 52ec1e4ea9e511dec3ae20e90d1a681d17b453eb..a00d3b7ded6c5e64619dbcdb25291b1c009a26db 100644 (file)
--- a/drivers/gpu/drm/tiny/cirrus-qemu.c
+++ b/drivers/gpu/drm/tiny/cirrus-qemu.c
@@ -318,7 +318,6 @@ static void cirrus_pitch_set(struct cirrus_device *cirrus, unsigned int pitch)
        /* Enable extended blanking and pitch bits, and enable full memory */
        cr1b = 0x22;
        cr1b |= (pitch >> 7) & 0x10;
-       cr1b |= (pitch >> 6) & 0x40;
        wreg_crt(cirrus, 0x1b, cr1b);
 
        cirrus_set_start_address(cirrus, 0);