From patchwork Fri Jan 6 20:08:00 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: William Zhang X-Patchwork-Id: 640305 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 0C3BCC3DA7A for ; Fri, 6 Jan 2023 20:10:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236189AbjAFUKU (ORCPT ); Fri, 6 Jan 2023 15:10:20 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48794 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236270AbjAFUKJ (ORCPT ); Fri, 6 Jan 2023 15:10:09 -0500 X-Greylist: delayed 65 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Fri, 06 Jan 2023 12:10:08 PST Received: from relay.smtp-ext.broadcom.com (lpdvsmtp11.broadcom.com [192.19.166.231]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F3BF4840A1; Fri, 6 Jan 2023 12:10:08 -0800 (PST) Received: from mail-lvn-it-01.lvn.broadcom.net (mail-lvn-it-01.lvn.broadcom.net [10.75.146.107]) by relay.smtp-ext.broadcom.com (Postfix) with ESMTP id 8933EC0000F3; Fri, 6 Jan 2023 12:10:08 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 relay.smtp-ext.broadcom.com 8933EC0000F3 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=broadcom.com; s=dkimrelay; t=1673035808; bh=PByAEycu10rflViW/6kaHG6GMcMou2/z7vIJQgSOhbY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ADlmj8ngphLysDXnVZdunyvPaZSKmSkxIBLrvhHwIXzFbuKV7k2lOAstPb72ONwLs KbTauncGWnyBaFePUYKueprnbm/BHLziYpRFlCFS/TeHyvfzdKX6FSQNdFmHvqoBAb 2CRvRFRNESP4ytkm6us3TodZMppMdcLww6lUog3w= Received: from bcacpedev-irv-3.lvn.broadcom.net (bcacpedev-irv-3.lvn.broadcom.net [10.75.138.105]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail-lvn-it-01.lvn.broadcom.net (Postfix) with ESMTPS id 8734618041CAC6; Fri, 6 Jan 2023 12:10:08 -0800 (PST) Received: by bcacpedev-irv-3.lvn.broadcom.net (Postfix, from userid 28376) id DDBE5101B33; Fri, 6 Jan 2023 12:10:01 -0800 (PST) From: William Zhang To: Linux SPI List , Broadcom Kernel List Cc: anand.gore@broadcom.com, tomer.yacoby@broadcom.com, dan.beygelman@broadcom.com, joel.peshkin@broadcom.com, f.fainelli@gmail.com, jonas.gorski@gmail.com, kursad.oney@broadcom.com, dregan@mail.com, William Zhang , Mark Brown , linux-kernel@vger.kernel.org Subject: [PATCH 08/16] spi: bcm63xx-hsspi: Handle cs_change correctly Date: Fri, 6 Jan 2023 12:08:00 -0800 Message-Id: <20230106200809.330769-9-william.zhang@broadcom.com> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20230106200809.330769-1-william.zhang@broadcom.com> References: <20230106200809.330769-1-william.zhang@broadcom.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-spi@vger.kernel.org The kernel SPI interface includes the cs_change flag that alters how the CS behaves. If we're in the middle of transfers, it tells us to unselect the CS momentarily since the target device requires that. If we're at the end of a transfer, it tells us to keep the CS selected, perhaps because the next transfer is likely targeted to the same device. We implement this scheme in the HSSPI driver in this change. Prior to this change, the CS would toggle momentarily if cs_change was set for the last transfer. This can be ignored by some or most devices, but the Microchip TPM2 device does not ignore it. With the change, the behavior is corrected and the 'glitch' is eliminated. Signed-off-by: Kursad Oney Signed-off-by: William Zhang --- drivers/spi/spi-bcm63xx-hsspi.c | 28 +++++++++++++++++++++------- 1 file changed, 21 insertions(+), 7 deletions(-) diff --git a/drivers/spi/spi-bcm63xx-hsspi.c b/drivers/spi/spi-bcm63xx-hsspi.c index 2b4cdf7e7002..f2b1b83bd6d4 100644 --- a/drivers/spi/spi-bcm63xx-hsspi.c +++ b/drivers/spi/spi-bcm63xx-hsspi.c @@ -290,6 +290,7 @@ static int bcm63xx_hsspi_transfer_one(struct spi_master *master, int status = -EINVAL; int dummy_cs; u32 reg; + bool restore_polarity = true; /* This controller does not support keeping CS active during idle. * To work around this, we use the following ugly hack: @@ -317,16 +318,29 @@ static int bcm63xx_hsspi_transfer_one(struct spi_master *master, spi_transfer_delay_exec(t); - if (t->cs_change) + /* + * cs_change rules: + * (1) cs_change = 0 && last_xfer = 0: + * Do not touch the CS. On to the next xfer. + * (2) cs_change = 1 && last_xfer = 0: + * Set cs = false before the next xfer. + * (3) cs_change = 0 && last_xfer = 1: + * We want CS to be deactivated. So do NOT set cs = false, + * instead just restore the original polarity. This has the + * same effect of deactivating the CS. + * (4) cs_change = 1 && last_xfer = 1: + * We want to keep CS active. So do NOT set cs = false, and + * make sure we do NOT reverse polarity. + */ + if (t->cs_change && !list_is_last(&t->transfer_list, &msg->transfers)) bcm63xx_hsspi_set_cs(bs, spi->chip_select, false); + + restore_polarity = !t->cs_change; } - mutex_lock(&bs->bus_mutex); - reg = __raw_readl(bs->regs + HSSPI_GLOBAL_CTRL_REG); - reg &= ~GLOBAL_CTRL_CS_POLARITY_MASK; - reg |= bs->cs_polarity; - __raw_writel(reg, bs->regs + HSSPI_GLOBAL_CTRL_REG); - mutex_unlock(&bs->bus_mutex); + bcm63xx_hsspi_set_cs(bs, dummy_cs, false); + if (restore_polarity) + bcm63xx_hsspi_set_cs(bs, spi->chip_select, false); msg->status = status; spi_finalize_current_message(master);