From dcf889956682d801d4a021a0f8bf34596bcf61c8 Mon Sep 17 00:00:00 2001 From: Samasth Norway Ananda Date: Mon, 16 Mar 2026 16:19:19 -0700 Subject: drm/i915/gmbus: fix spurious timeout on 512-byte burst reads [ Upstream commit 08441f10f4dc09fdeb64529953ac308abc79dd38 ] 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 Signed-off-by: Sasha Levin --- drivers/gpu/drm/i915/display/intel_gmbus.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'drivers/gpu') diff --git a/drivers/gpu/drm/i915/display/intel_gmbus.c b/drivers/gpu/drm/i915/display/intel_gmbus.c index 795012d7c24c..5a941bea81ca 100644 --- a/drivers/gpu/drm/i915/display/intel_gmbus.c +++ b/drivers/gpu/drm/i915/display/intel_gmbus.c @@ -498,8 +498,10 @@ 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; -- cgit v1.2.3