From mboxrd@z Thu Jan 1 00:00:00 1970 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 CDD12C77B7C for ; Tue, 9 May 2023 16:42:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231488AbjEIQmO (ORCPT ); Tue, 9 May 2023 12:42:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56512 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229489AbjEIQmG (ORCPT ); Tue, 9 May 2023 12:42:06 -0400 Received: from mx0b-001ae601.pphosted.com (mx0b-001ae601.pphosted.com [67.231.152.168]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 35CEF3C35; Tue, 9 May 2023 09:42:05 -0700 (PDT) Received: from pps.filterd (m0077474.ppops.net [127.0.0.1]) by mx0b-001ae601.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 349GKZNL008998; Tue, 9 May 2023 11:41:55 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cirrus.com; h=from : to : cc : subject : date : message-id : mime-version : content-transfer-encoding : content-type; s=PODMain02222019; bh=qQM04fH8wYbMYV9sluxk+y4zEawLXJoiozfeS8Zvv7M=; b=OuuAD7036JIIFa4hLIuHWmPNDMXr4O26A8SdnlCO6CRuI21Q1vwabgcDnLaVL2yfjmrJ qxzBj0lTfOjBTqSPQR/7DGUzhzdeiTexUxjRIVBXkYJTt0JfJTLOf/SGb9ErDQiGvSJH gmvfgrZxXXXrTry2CvhFEdY7BEsLcdKSL3jxJwz9SZE01PUO/5GJpOfmrM1KPrg4g8/i 5pxMmWSGIoSQjYvwM8Jx9Z+XNDE0M9ODurjTYbOuq9y4/G6KKWxUfr8daefsHMlqa2bh Z5adhmtkOCA2oxSnFuYvh2SouD7y0JNKnWEKLb/0KnDxqTzOYGZ6JRKwzSWiYTyq8yM9 lw== Received: from ediex01.ad.cirrus.com ([84.19.233.68]) by mx0b-001ae601.pphosted.com (PPS) with ESMTPS id 3qf7s41ahu-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 09 May 2023 11:41:54 -0500 Received: from ediex02.ad.cirrus.com (198.61.84.81) by ediex01.ad.cirrus.com (198.61.84.80) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.26; Tue, 9 May 2023 11:41:53 -0500 Received: from ediswmail.ad.cirrus.com (198.61.86.93) by anon-ediex02.ad.cirrus.com (198.61.84.81) with Microsoft SMTP Server id 15.2.1118.26 via Frontend Transport; Tue, 9 May 2023 11:41:53 -0500 Received: from algalon.ad.cirrus.com (algalon.ad.cirrus.com [198.90.251.122]) by ediswmail.ad.cirrus.com (Postfix) with ESMTP id 2C58011D4; Tue, 9 May 2023 16:41:53 +0000 (UTC) From: Charles Keepax To: CC: , , , Subject: [PATCH 1/2] spi: spi-cadence: Avoid read of RX FIFO before its ready Date: Tue, 9 May 2023 17:41:52 +0100 Message-ID: <20230509164153.3907694-1-ckeepax@opensource.cirrus.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Proofpoint-ORIG-GUID: PMVYRC2i7GEEEdQKK_jielB5LHBdePS9 X-Proofpoint-GUID: PMVYRC2i7GEEEdQKK_jielB5LHBdePS9 X-Proofpoint-Spam-Reason: safe Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Recent changes to cdns_spi_irq introduced some issues. Firstly, when writing the end of a longer transaction, the code in cdns_spi_irq will write data into the TX FIFO, then immediately fall into the if (!xspi->tx_bytes) path and attempt to read data from the RX FIFO. However this required waiting for the TX FIFO to empty before the RX data was ready. Secondly, the variable trans_cnt is now rather inaccurately named since in cases, where the watermark is set to 1, trans_cnt will be 1 but the count of bytes transferred would be much longer. Finally, when setting up the transaction we set the watermark to 50% of the FIFO if the transaction is great than 50% of the FIFO. However, there is no need to split a tranaction that is smaller than the whole FIFO, so anything up to the FIFO size can be done in a single transaction. Tidy up the code a little, to avoid repeatedly calling cdns_spi_read_rx_fifo with a count of 1, and correct the three issues noted above. Fixes: b1b90514eaa3 ("spi: spi-cadence: Add support for Slave mode") Signed-off-by: Charles Keepax --- drivers/spi/spi-cadence.c | 42 ++++++++++++++------------------------- 1 file changed, 15 insertions(+), 27 deletions(-) diff --git a/drivers/spi/spi-cadence.c b/drivers/spi/spi-cadence.c index ac85d55622127..b0ccb138e3566 100644 --- a/drivers/spi/spi-cadence.c +++ b/drivers/spi/spi-cadence.c @@ -304,13 +304,11 @@ static int cdns_spi_setup_transfer(struct spi_device *spi, * cdns_spi_fill_tx_fifo - Fills the TX FIFO with as many bytes as possible * @xspi: Pointer to the cdns_spi structure */ -static void cdns_spi_fill_tx_fifo(struct cdns_spi *xspi) +static void cdns_spi_fill_tx_fifo(struct cdns_spi *xspi, unsigned int avail) { unsigned long trans_cnt = 0; - while ((trans_cnt < xspi->tx_fifo_depth) && - (xspi->tx_bytes > 0)) { - + while ((trans_cnt < avail) && (xspi->tx_bytes > 0)) { /* When xspi in busy condition, bytes may send failed, * then spi control did't work thoroughly, add one byte delay */ @@ -381,33 +379,23 @@ static irqreturn_t cdns_spi_irq(int irq, void *dev_id) spi_finalize_current_transfer(ctlr); status = IRQ_HANDLED; } else if (intr_status & CDNS_SPI_IXR_TXOW) { - int trans_cnt = cdns_spi_read(xspi, CDNS_SPI_THLD); + int threshold = cdns_spi_read(xspi, CDNS_SPI_THLD); + int trans_cnt = xspi->rx_bytes - xspi->tx_bytes; + + if (threshold > 1) + trans_cnt -= threshold; + /* Set threshold to one if number of pending are * less than half fifo */ if (xspi->tx_bytes < xspi->tx_fifo_depth >> 1) cdns_spi_write(xspi, CDNS_SPI_THLD, 1); - while (trans_cnt) { - cdns_spi_read_rx_fifo(xspi, 1); - - if (xspi->tx_bytes) { - if (xspi->txbuf) - cdns_spi_write(xspi, CDNS_SPI_TXD, - *xspi->txbuf++); - else - cdns_spi_write(xspi, CDNS_SPI_TXD, 0); - xspi->tx_bytes--; - } - trans_cnt--; - } - if (!xspi->tx_bytes) { - /* Fixed delay due to controller limitation with - * RX_NEMPTY incorrect status - * Xilinx AR:65885 contains more details - */ - udelay(10); - cdns_spi_read_rx_fifo(xspi, xspi->rx_bytes); + cdns_spi_read_rx_fifo(xspi, trans_cnt); + + if (xspi->tx_bytes) { + cdns_spi_fill_tx_fifo(xspi, trans_cnt); + } else { cdns_spi_write(xspi, CDNS_SPI_IDR, CDNS_SPI_IXR_DEFAULT); spi_finalize_current_transfer(ctlr); @@ -456,10 +444,10 @@ static int cdns_transfer_one(struct spi_controller *ctlr, /* Set TX empty threshold to half of FIFO depth * only if TX bytes are more than half FIFO depth. */ - if (xspi->tx_bytes > (xspi->tx_fifo_depth >> 1)) + if (xspi->tx_bytes > xspi->tx_fifo_depth) cdns_spi_write(xspi, CDNS_SPI_THLD, xspi->tx_fifo_depth >> 1); - cdns_spi_fill_tx_fifo(xspi); + cdns_spi_fill_tx_fifo(xspi, xspi->tx_fifo_depth); spi_transfer_delay_exec(transfer); cdns_spi_write(xspi, CDNS_SPI_IER, CDNS_SPI_IXR_DEFAULT); -- 2.30.2