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 E391B3DD507; Tue, 31 Mar 2026 16:27:18 +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=1774974439; cv=none; b=n2ofVxFEXWeo4p73naZgKxAPEVFD5YwyonpK3qe80hPz2ZFFS1loskRQfoFpp4q3CO14S9rHrlKz/FNYiMilaDAj1pFRZnYdX64O7C35NALPHy41OjU4Ynqh0k44l7RQb2IB8rk0FD1Nr4J7rJwkTLjy2xhvL5JBb06Pq/xEmLY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774974439; c=relaxed/simple; bh=7AJQghWNnWJDLtpotECSiHq000wNjL9mikXL6CROTP8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=N56jwHYvuqZcuEcN/qB2REN2+ZUAaWRXt/mmXeZ9lITNvmjBOyGbqVg3vbys1SFHYHW+ceDBJNyQ+qliVzuFMHhjJ8//roOf8uj/nc66dpRojldDVoUyUvQ4mdLiXXSIYoyPYjiUDnKnxbslQH6DjVf8ru5QDJ5tX7NjjkkfKu0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=2IDvL2TH; 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="2IDvL2TH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 79CC7C19423; Tue, 31 Mar 2026 16:27:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1774974438; bh=7AJQghWNnWJDLtpotECSiHq000wNjL9mikXL6CROTP8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=2IDvL2THlxYer25w5waiL4nfVAyojh3msfhZkdz0Pn0Cja4OJExZI1fZvbHu1gRcn neUKBKnqxRTgPn49iAq/H+mD3rT/P1jkrcC0YHlLoiEXpjejvwe2rp77tjmPLmYzQa L85HmUaS1yaeUsPo9IJOdzkougc8X9XiKZaWfZNM= 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 6.6 086/175] drm/i915/gmbus: fix spurious timeout on 512-byte burst reads Date: Tue, 31 Mar 2026 18:21:10 +0200 Message-ID: <20260331161732.931341680@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260331161729.779738837@linuxfoundation.org> References: <20260331161729.779738837@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 6.6-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 e95ddb580ef6c..a01e655c24ff3 100644 --- a/drivers/gpu/drm/i915/display/intel_gmbus.c +++ b/drivers/gpu/drm/i915/display/intel_gmbus.c @@ -460,8 +460,10 @@ gmbus_xfer_read_chunk(struct drm_i915_private *i915, val = intel_de_read_fw(i915, GMBUS3(i915)); do { - if (extra_byte_added && len == 1) + if (extra_byte_added && len == 1) { + len--; break; + } *buf++ = val & 0xff; val >>= 8; -- 2.53.0