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 9CF1CCCA47B for ; Tue, 28 Jun 2022 02:34:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245058AbiF1CeN (ORCPT ); Mon, 27 Jun 2022 22:34:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40394 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244870AbiF1C2O (ORCPT ); Mon, 27 Jun 2022 22:28:14 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 17F4426135; Mon, 27 Jun 2022 19:27:04 -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 ams.source.kernel.org (Postfix) with ESMTPS id B7F82B81C00; Tue, 28 Jun 2022 02:27:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C0849C385A9; Tue, 28 Jun 2022 02:27:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1656383221; bh=S7jEa6xG+B2e0s2HleouPBIsGfYT39anPZPoYI3zjHA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=iy1TwN9eMXbbJQJjkmD5T76sJCZS0B1X7AYKo7ggEj53twJE/a7QNtOA/xXfmm/HW 85jbElnz3iwhZSS429Gp6gk5fdLP2xuXV6z6UqsN7bbNLVpE6SEJz9EQS2nWNVsSma dZHwlB62it8xg30Ny8l8NUUgra2NKyOvlicfampTRvCr90LLiYRonIEIdiOkYvwvxz M0kbw1gQopvCIrmcR2f6DasEgdTo7UTG5RVprKCPGZz3/hoL1J10M1s097ECkkyG3l NFeonENFp8i6mcBoIXwp9og5LGgpSAwt4ixqn2QuhFImPB6hiyAkG2QnPnDYLbjJ1Q sJa9vJwBQTB8w== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Lars-Peter Clausen , Mark Brown , Sasha Levin , linux-spi@vger.kernel.org Subject: [PATCH AUTOSEL 4.9 02/13] spi: cadence: Detect transmit FIFO depth Date: Mon, 27 Jun 2022 22:26:46 -0400 Message-Id: <20220628022657.597208-2-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220628022657.597208-1-sashal@kernel.org> References: <20220628022657.597208-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Lars-Peter Clausen [ Upstream commit 7b40322f7183a92c4303457528ae7cda571c60b9 ] The depth of the transmit FIFO for the Cadence SPI controller is currently hardcoded to 128. But the depth is a synthesis configuration parameter of the core and can vary between different SoCs. If the configured FIFO size is less than 128 the driver will busy loop in the cdns_spi_fill_tx_fifo() function waiting for FIFO space to become available. Depending on the length and speed of the transfer it can spin for a significant amount of time. The cdns_spi_fill_tx_fifo() function is called from the drivers interrupt handler, so it can leave interrupts disabled for a prolonged amount of time. In addition the read FIFO will also overflow and data will be discarded. To avoid this detect the actual size of the FIFO and use that rather than the hardcoded value. To detect the FIFO size the FIFO threshold register is used. The register is sized so that it can hold FIFO size - 1 as its maximum value. Bits that are not needed to hold the threshold value will always read 0. By writing 0xffff to the register and then reading back the value in the register we get the FIFO size. Signed-off-by: Lars-Peter Clausen Link: https://lore.kernel.org/r/20220527091143.3780378-1-lars@metafoo.de Signed-off-by: Mark Brown Signed-off-by: Sasha Levin --- drivers/spi/spi-cadence.c | 27 +++++++++++++++++++++++---- 1 file changed, 23 insertions(+), 4 deletions(-) diff --git a/drivers/spi/spi-cadence.c b/drivers/spi/spi-cadence.c index 6d294a1fa5e5..733724e71a30 100644 --- a/drivers/spi/spi-cadence.c +++ b/drivers/spi/spi-cadence.c @@ -96,9 +96,6 @@ #define CDNS_SPI_ER_ENABLE 0x00000001 /* SPI Enable Bit Mask */ #define CDNS_SPI_ER_DISABLE 0x0 /* SPI Disable Bit Mask */ -/* SPI FIFO depth in bytes */ -#define CDNS_SPI_FIFO_DEPTH 128 - /* Default number of chip select lines */ #define CDNS_SPI_DEFAULT_NUM_CS 4 @@ -114,6 +111,7 @@ * @rx_bytes: Number of bytes requested * @dev_busy: Device busy flag * @is_decoded_cs: Flag for decoder property set or not + * @tx_fifo_depth: Depth of the TX FIFO */ struct cdns_spi { void __iomem *regs; @@ -127,6 +125,7 @@ struct cdns_spi { int rx_bytes; u8 dev_busy; u32 is_decoded_cs; + unsigned int tx_fifo_depth; }; /* Macros for the SPI controller read/write */ @@ -308,7 +307,7 @@ static void cdns_spi_fill_tx_fifo(struct cdns_spi *xspi) { unsigned long trans_cnt = 0; - while ((trans_cnt < CDNS_SPI_FIFO_DEPTH) && + while ((trans_cnt < xspi->tx_fifo_depth) && (xspi->tx_bytes > 0)) { if (xspi->txbuf) cdns_spi_write(xspi, CDNS_SPI_TXD, *xspi->txbuf++); @@ -463,6 +462,24 @@ static int cdns_unprepare_transfer_hardware(struct spi_master *master) return 0; } +/** + * cdns_spi_detect_fifo_depth - Detect the FIFO depth of the hardware + * @xspi: Pointer to the cdns_spi structure + * + * The depth of the TX FIFO is a synthesis configuration parameter of the SPI + * IP. The FIFO threshold register is sized so that its maximum value can be the + * FIFO size - 1. This is used to detect the size of the FIFO. + */ +static void cdns_spi_detect_fifo_depth(struct cdns_spi *xspi) +{ + /* The MSBs will get truncated giving us the size of the FIFO */ + cdns_spi_write(xspi, CDNS_SPI_THLD, 0xffff); + xspi->tx_fifo_depth = cdns_spi_read(xspi, CDNS_SPI_THLD) + 1; + + /* Reset to default */ + cdns_spi_write(xspi, CDNS_SPI_THLD, 0x1); +} + /** * cdns_spi_probe - Probe method for the SPI driver * @pdev: Pointer to the platform_device structure @@ -536,6 +553,8 @@ static int cdns_spi_probe(struct platform_device *pdev) if (ret < 0) xspi->is_decoded_cs = 0; + cdns_spi_detect_fifo_depth(xspi); + /* SPI controller initializations */ cdns_spi_init_hw(xspi); -- 2.35.1