From nobody Wed Dec 17 09:12:16 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A9119C32772 for ; Tue, 23 Aug 2022 10:43:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1355503AbiHWKnh (ORCPT ); Tue, 23 Aug 2022 06:43:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57058 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353973AbiHWKcy (ORCPT ); Tue, 23 Aug 2022 06:32:54 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 27B26A59B2; Tue, 23 Aug 2022 02:06:51 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id D63066155D; Tue, 23 Aug 2022 09:06:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DB8B8C433D7; Tue, 23 Aug 2022 09:06:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1661245610; bh=go/Haau0lthCUe3VavTCa+hFobbLbcMtiNUfAjzIzeU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=aF+ImNbrw6DcEpkeDSSwKckfi/U1R6doISK72LlKEByJCabtcjoqkK8Ix9cAbEEbm O5wOS5uE3A4XaqRZEYWkrdFHNqGZ+Kp8vhKZLX2qplFRL+KkdqzkJv+bwUbKZsYBsg FWiUVr+EO0x7AtA4W9xkN3DJsAM6WwOvBPxmQK/s= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Lars-Peter Clausen , Shubhrajyoti Datta , Wolfram Sang , Sasha Levin Subject: [PATCH 4.19 105/287] i2c: cadence: Support PEC for SMBus block read Date: Tue, 23 Aug 2022 10:24:34 +0200 Message-Id: <20220823080103.911961465@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220823080100.268827165@linuxfoundation.org> References: <20220823080100.268827165@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Lars-Peter Clausen [ Upstream commit 9fdf6d97f03035ad5298e2d1635036c74c2090ed ] SMBus packet error checking (PEC) is implemented by appending one additional byte of checksum data at the end of the message. This provides additional protection and allows to detect data corruption on the I2C bus. SMBus block reads support variable length reads. The first byte in the read message is the number of available data bytes. The combination of PEC and block read is currently not supported by the Cadence I2C driver. * When PEC is enabled the maximum transfer length for block reads increases from 33 to 34 bytes. * The I2C core smbus emulation layer relies on the driver updating the `i2c_msg` `len` field with the number of received bytes. The updated length is used when checking the PEC. Add support to the Cadence I2C driver for handling SMBus block reads with PEC. To determine the maximum transfer length uses the initial `len` value of the `i2c_msg`. When PEC is enabled this will be 2, when it is disabled it will be 1. Once a read transfer is done also increment the `len` field by the amount of received data bytes. This change has been tested with a UCM90320 PMBus power monitor, which requires block reads to access certain data fields, but also has PEC enabled by default. Fixes: df8eb5691c48 ("i2c: Add driver for Cadence I2C controller") Signed-off-by: Lars-Peter Clausen Tested-by: Shubhrajyoti Datta Signed-off-by: Wolfram Sang Signed-off-by: Sasha Levin --- drivers/i2c/busses/i2c-cadence.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/drivers/i2c/busses/i2c-cadence.c b/drivers/i2c/busses/i2c-cade= nce.c index 512c61d31fe5..bce7bf93d62a 100644 --- a/drivers/i2c/busses/i2c-cadence.c +++ b/drivers/i2c/busses/i2c-cadence.c @@ -353,8 +353,13 @@ static void cdns_i2c_mrecv(struct cdns_i2c *id) ctrl_reg =3D cdns_i2c_readreg(CDNS_I2C_CR_OFFSET); ctrl_reg |=3D CDNS_I2C_CR_RW | CDNS_I2C_CR_CLR_FIFO; =20 + /* + * Receive up to I2C_SMBUS_BLOCK_MAX data bytes, plus one message length + * byte, plus one checksum byte if PEC is enabled. p_msg->len will be 2 if + * PEC is enabled, otherwise 1. + */ if (id->p_msg->flags & I2C_M_RECV_LEN) - id->recv_count =3D I2C_SMBUS_BLOCK_MAX + 1; + id->recv_count =3D I2C_SMBUS_BLOCK_MAX + id->p_msg->len; =20 id->curr_recv_count =3D id->recv_count; =20 @@ -540,6 +545,9 @@ static int cdns_i2c_process_msg(struct cdns_i2c *id, st= ruct i2c_msg *msg, if (id->err_status & CDNS_I2C_IXR_ARB_LOST) return -EAGAIN; =20 + if (msg->flags & I2C_M_RECV_LEN) + msg->len +=3D min_t(unsigned int, msg->buf[0], I2C_SMBUS_BLOCK_MAX); + return 0; } =20 --=20 2.35.1