From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753877Ab2IQAuj (ORCPT ); Sun, 16 Sep 2012 20:50:39 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:33386 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753052Ab2IQAtj (ORCPT ); Sun, 16 Sep 2012 20:49:39 -0400 Message-Id: <20120917003638.813933543@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Mon, 17 Sep 2012 01:37:56 +0100 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, =?UTF-8?q?Beno=C3=AEt=20Locher?= , Marc Kleine-Budde Subject: [ 091/135] can: mcp251x: avoid repeated frame bug In-Reply-To: <20120917003625.784119135@decadent.org.uk> X-SA-Exim-Connect-IP: 2001:470:1f08:1539:21c:bfff:fe03:f805 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Benoît Locher commit cab32f39dcc5b35db96497dc0a026b5dea76e4e7 upstream. The MCP2515 has a silicon bug causing repeated frame transmission, see section 5 of MCP2515 Rev. B Silicon Errata Revision G (March 2007). Basically, setting TXBnCTRL.TXREQ in either SPI mode (00 or 11) will eventually cause the bug. The workaround proposed by Microchip is to use mode 00 and send a RTS command on the SPI bus to initiate the transmission. Signed-off-by: Benoît Locher Signed-off-by: Marc Kleine-Budde Signed-off-by: Ben Hutchings --- drivers/net/can/mcp251x.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/drivers/net/can/mcp251x.c b/drivers/net/can/mcp251x.c index a580db2..26e7129 100644 --- a/drivers/net/can/mcp251x.c +++ b/drivers/net/can/mcp251x.c @@ -83,6 +83,11 @@ #define INSTRUCTION_LOAD_TXB(n) (0x40 + 2 * (n)) #define INSTRUCTION_READ_RXB(n) (((n) == 0) ? 0x90 : 0x94) #define INSTRUCTION_RESET 0xC0 +#define RTS_TXB0 0x01 +#define RTS_TXB1 0x02 +#define RTS_TXB2 0x04 +#define INSTRUCTION_RTS(n) (0x80 | ((n) & 0x07)) + /* MPC251x registers */ #define CANSTAT 0x0e @@ -397,6 +402,7 @@ static void mcp251x_hw_tx_frame(struct spi_device *spi, u8 *buf, static void mcp251x_hw_tx(struct spi_device *spi, struct can_frame *frame, int tx_buf_idx) { + struct mcp251x_priv *priv = dev_get_drvdata(&spi->dev); u32 sid, eid, exide, rtr; u8 buf[SPI_TRANSFER_BUF_LEN]; @@ -418,7 +424,10 @@ static void mcp251x_hw_tx(struct spi_device *spi, struct can_frame *frame, buf[TXBDLC_OFF] = (rtr << DLC_RTR_SHIFT) | frame->can_dlc; memcpy(buf + TXBDAT_OFF, frame->data, frame->can_dlc); mcp251x_hw_tx_frame(spi, buf, frame->can_dlc, tx_buf_idx); - mcp251x_write_reg(spi, TXBCTRL(tx_buf_idx), TXBCTRL_TXREQ); + + /* use INSTRUCTION_RTS, to avoid "repeated frame problem" */ + priv->spi_tx_buf[0] = INSTRUCTION_RTS(1 << tx_buf_idx); + mcp251x_spi_trans(priv->spi, 1); } static void mcp251x_hw_rx_frame(struct spi_device *spi, u8 *buf,