From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2E4B12E11A6; Tue, 31 Mar 2026 17:03:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774976595; cv=none; b=Blh4GC3bD0NrQ1Pt2WlrcnbHsaQSS2lMVkegDqU0THdrP1NBj3byWF/XSaOkHVmwXWEfGjVB+rxX1XfAWZfqYPGoCSnPvmFhXWMmVVkSozLEa+AV3nayoF3lsIfn7njfa1on/xczUhdg6XAmGHbAtvPeFYkhSV1QhmqKjWcu/Pk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774976595; c=relaxed/simple; bh=c19AXWTaCdotqGQZNzqo8aFEHE8evXlfNbm1ygkSEBA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=TlhACoQM3HjLAkObiZo8x3scxAvTp5jkWF6ZkXjo0zxyfFj3e7KKbXhC1TYR83TL4FHzfKkuRJ7ZXHcGvIdNifdJVlmVL2b0gN0Yy/CLbnU46784Utb/Sxd/pMyUSBP9XnTu8dAxO0NVNxwliGCtVWw7ik6YojnYNwjpb6IropQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=tp21jro9; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="tp21jro9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BC6D0C2BCB2; Tue, 31 Mar 2026 17:03:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1774976595; bh=c19AXWTaCdotqGQZNzqo8aFEHE8evXlfNbm1ygkSEBA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tp21jro9cPXG7XSOlC/mAxcyD0JCjmG+2WdW29XQtwMRT0jcueIiSBAAoadjhV7G5 6fQDy8RQH6NeSdtJJDuwi7uFDotep/s9dOJXdBjW8tCQ1Ew7xf9KCPwxW1vpmz3gZx 3RlZ8jR47xvRSvNq1/jPwyVBpBgjQ5VD7CP68pak= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Samasth Norway Ananda , Jani Nikula , Joonas Lahtinen , Sasha Levin Subject: [PATCH 6.18 153/309] drm/i915/gmbus: fix spurious timeout on 512-byte burst reads Date: Tue, 31 Mar 2026 18:20:56 +0200 Message-ID: <20260331161759.101585127@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260331161753.468533260@linuxfoundation.org> References: <20260331161753.468533260@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Samasth Norway Ananda [ 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(-) diff --git a/drivers/gpu/drm/i915/display/intel_gmbus.c b/drivers/gpu/drm/i915/display/intel_gmbus.c index 358210adb8f84..10b3f3969c960 100644 --- a/drivers/gpu/drm/i915/display/intel_gmbus.c +++ b/drivers/gpu/drm/i915/display/intel_gmbus.c @@ -497,8 +497,10 @@ 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; -- 2.53.0