From patchwork Thu Aug 18 13:57:49 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christophe Leroy X-Patchwork-Id: 12947168 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 A3AC8C00140 for ; Thu, 18 Aug 2022 13:58:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245463AbiHRN6b (ORCPT ); Thu, 18 Aug 2022 09:58:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34458 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245485AbiHRN6P (ORCPT ); Thu, 18 Aug 2022 09:58:15 -0400 Received: from pegase2.c-s.fr (pegase2.c-s.fr [93.17.235.10]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E39D82E3; Thu, 18 Aug 2022 06:58:11 -0700 (PDT) Received: from localhost (mailhub3.si.c-s.fr [172.26.127.67]) by localhost (Postfix) with ESMTP id 4M7mgQ0Yqsz9sf4; Thu, 18 Aug 2022 15:58:10 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from pegase2.c-s.fr ([172.26.127.65]) by localhost (pegase2.c-s.fr [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Mh1iG2BKyRO9; Thu, 18 Aug 2022 15:58:10 +0200 (CEST) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase2.c-s.fr (Postfix) with ESMTP id 4M7mgP6sZWz9sdy; Thu, 18 Aug 2022 15:58:09 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id DC8B78B767; Thu, 18 Aug 2022 15:58:09 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id LlPoFkLgpU30; Thu, 18 Aug 2022 15:58:09 +0200 (CEST) Received: from PO20335.IDSI0.si.c-s.fr (unknown [192.168.235.236]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 9D11C8B763; Thu, 18 Aug 2022 15:58:09 +0200 (CEST) Received: from PO20335.IDSI0.si.c-s.fr (localhost [127.0.0.1]) by PO20335.IDSI0.si.c-s.fr (8.17.1/8.16.1) with ESMTPS id 27IDw0Vu1993063 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Thu, 18 Aug 2022 15:58:00 +0200 Received: (from chleroy@localhost) by PO20335.IDSI0.si.c-s.fr (8.17.1/8.17.1/Submit) id 27IDw09J1993060; Thu, 18 Aug 2022 15:58:00 +0200 X-Authentication-Warning: PO20335.IDSI0.si.c-s.fr: chleroy set sender to christophe.leroy@csgroup.eu using -f From: Christophe Leroy To: Mark Brown Cc: Christophe Leroy , linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org Subject: [PATCH v3] spi: Add capability to perform some transfer with chipselect off Date: Thu, 18 Aug 2022 15:57:49 +0200 Message-Id: X-Mailer: git-send-email 2.37.1 MIME-Version: 1.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1660831067; l=3497; s=20211009; h=from:subject:message-id; bh=pBEp2sV1HSEbreVLmDNueVNSIkEvPWM2zi6OQ+L8A3M=; b=ruZBrXja6jNd1n+ZvqAsoBgHCZ9iAZPljuFSoWxEqAaOztZftEi4UMQVPPKMcs+KQxOnaWQ/yslv 5ExyNtw1AaL2/5vYPGW7ZLIbVNRNFIBeTu9RkgKriygiTi0QfmlV X-Developer-Key: i=christophe.leroy@csgroup.eu; a=ed25519; pk=HIzTzUj91asvincQGOFx6+ZF5AoUuP9GdOtQChs7Mm0= Precedence: bulk List-ID: X-Mailing-List: linux-spi@vger.kernel.org Some components require a few clock cycles with chipselect off before or/and after the data transfer done with CS on. Typically IDT 801034 QUAD PCM CODEC datasheet states "Note *: CCLK should have one cycle before CS goes low, and two cycles after CS goes high". The cycles "before" are implicitely provided by all previous activity on the SPI bus. But the cycles "after" must be provided in order to terminate the SPI transfer. In order to use that kind of component, add a cs_off flag to spi_transfer struct. When this flag is set, the transfer is performed with chipselect off. This allows consummer to add a dummy transfer at the end of the transfer list which is performed with chipselect OFF, providing the required additional clock cycles. Signed-off-by: Christophe Leroy --- This is a change in the approach. Now we offer the driver/consumer a way to perform an additional transfer with chipselect off. v2 is at https://patchwork.kernel.org/project/spi-devel-general/list/?series=618784&state=*&archive=both drivers/spi/spi.c | 12 +++++++++--- include/linux/spi/spi.h | 2 ++ 2 files changed, 11 insertions(+), 3 deletions(-) diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index 2a472dcf081e..ca71723d44a7 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -1418,7 +1418,8 @@ static int spi_transfer_one_message(struct spi_controller *ctlr, struct spi_statistics *statm = &ctlr->statistics; struct spi_statistics *stats = &msg->spi->statistics; - spi_set_cs(msg->spi, true, false); + xfer = list_first_entry(&msg->transfers, struct spi_transfer, transfer_list); + spi_set_cs(msg->spi, !xfer->cs_off, false); SPI_STATISTICS_INCREMENT_FIELD(statm, messages); SPI_STATISTICS_INCREMENT_FIELD(stats, messages); @@ -1486,10 +1487,15 @@ static int spi_transfer_one_message(struct spi_controller *ctlr, &msg->transfers)) { keep_cs = true; } else { - spi_set_cs(msg->spi, false, false); + if (!xfer->cs_off) + spi_set_cs(msg->spi, false, false); _spi_transfer_cs_change_delay(msg, xfer); - spi_set_cs(msg->spi, true, false); + if (!list_next_entry(xfer, transfer_list)->cs_off) + spi_set_cs(msg->spi, true, false); } + } else if (!list_is_last(&xfer->transfer_list, &msg->transfers) && + xfer->cs_off != list_next_entry(xfer, transfer_list)->cs_off) { + spi_set_cs(msg->spi, xfer->cs_off, false); } msg->actual_length += xfer->len; diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index 7ab3fed7b804..cbb787f6b9ff 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -818,6 +818,7 @@ struct spi_res { * for this transfer. If 0 the default (from @spi_device) is used. * @dummy_data: indicates transfer is dummy bytes transfer. * @cs_change: affects chipselect after this transfer completes + * @cs_off: performs the transfer with chipselect off. * @cs_change_delay: delay between cs deassert and assert when * @cs_change is set and @spi_transfer is not the last in @spi_message * @delay: delay to be introduced after this transfer before @@ -930,6 +931,7 @@ struct spi_transfer { unsigned cs_change:1; unsigned tx_nbits:3; unsigned rx_nbits:3; + unsigned cs_off:1; #define SPI_NBITS_SINGLE 0x01 /* 1bit transfer */ #define SPI_NBITS_DUAL 0x02 /* 2bits transfer */ #define SPI_NBITS_QUAD 0x04 /* 4bits transfer */