From: Samasth Norway Ananda Date: Mon, 16 Mar 2026 23:19:19 +0000 (-0700) Subject: drm/i915/gmbus: fix spurious timeout on 512-byte burst reads X-Git-Tag: v7.0-rc6~19^2~3^2~3 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=08441f10f4dc09fdeb64529953ac308abc79dd38;p=thirdparty%2Fkernel%2Flinux.git drm/i915/gmbus: fix spurious timeout on 512-byte burst reads When reading exactly 512 bytes with burst read enabled, the extra_byte_added path breaks out of the inner do-while without decrementing len. The outer while(len) then re-enters and gmbus_wait() times out since all data has been delivered. Decrement len before the break so the outer loop terminates correctly. Fixes: d5dc0f43f268 ("drm/i915/gmbus: Enable burst read") Signed-off-by: Samasth Norway Ananda Reviewed-by: Jani Nikula Link: https://patch.msgid.link/20260316231920.135438-2-samasth.norway.ananda@oracle.com Signed-off-by: Jani Nikula (cherry picked from commit 4ab0f09ee73fc853d00466682635f67c531f909c) Signed-off-by: Joonas Lahtinen --- diff --git a/drivers/gpu/drm/i915/display/intel_gmbus.c b/drivers/gpu/drm/i915/display/intel_gmbus.c index a7bce0c6a17e..264e6843bff1 100644 --- a/drivers/gpu/drm/i915/display/intel_gmbus.c +++ b/drivers/gpu/drm/i915/display/intel_gmbus.c @@ -496,8 +496,10 @@ gmbus_xfer_read_chunk(struct intel_display *display, val = intel_de_read_fw(display, GMBUS3(display)); do { - if (extra_byte_added && len == 1) + if (extra_byte_added && len == 1) { + len--; break; + } *buf++ = val & 0xff; val >>= 8;