From patchwork Thu May 20 20:02:22 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vladimir Oltean X-Patchwork-Id: 443754 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 81D78C433B4 for ; Thu, 20 May 2021 20:02:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 648A26128A for ; Thu, 20 May 2021 20:02:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240006AbhETUEF (ORCPT ); Thu, 20 May 2021 16:04:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47200 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237551AbhETUEE (ORCPT ); Thu, 20 May 2021 16:04:04 -0400 Received: from mail-ed1-x529.google.com (mail-ed1-x529.google.com [IPv6:2a00:1450:4864:20::529]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3044DC061761; Thu, 20 May 2021 13:02:41 -0700 (PDT) Received: by mail-ed1-x529.google.com with SMTP id y7so3290344eda.2; Thu, 20 May 2021 13:02:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=FHUJtBq9iJ9xTw4W3wJ7q5IXipUFvoldRp8Yq4IjtY4=; b=FXbDVMvnvTYdQA26aNNwxZnQEBqU+sXeFiVKTC/zSjlrZ1k3A5FerLTxVjqSaIlsPb dDsMj/BZK+lhUfs/Nsb4C4Y3N4W1t91mm/S3UkzKa6bmwrk9A5krW0ykHoisP8J7z6Pj aBt4pf12jKYYSlc1ev7F96IZMIlnDJdiuASaz1bhmG2cahIcnBbGRMYRg8+V9hIzsYe1 NC64bQwLH3+rVIoMFws5pqgdoe5lsdG1sOFv6GaeuW2z/yWajk8GGFJK+HAmsQNZZeKo VWFAnDYHMQ6seNqtP/vhFnTeXi53rSV5wYovYGiuP1KAO3kj13Bd/BqzeyzoTtejMWD4 xduw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=FHUJtBq9iJ9xTw4W3wJ7q5IXipUFvoldRp8Yq4IjtY4=; b=HOZCT+B7Rlb0uKzoD9k1taoU2m6KKvH6rLFpZo3JPCxVF/2yVLXVVM3CBqb6tWtQVm mrPMTdRZiL5fvsgk8LaYqCnXcrq6Ji77QqZnAhg8kbXLU7Rui4x2l9T9jYPlMVCGL5Hf WquYIfAcPa1obPOcyn7KydlKyTLAeD5F0K7KYdzTiER6FlxzDYmcO/VlQTnZkJk2LD/i NbNW81N3dF+SMYSEnZDoHvcLWDzs72WByzR1Ivl9IO+ZpVZz9P11ya4rJCYD+HEF24ft SMQXyf3LbO4GPfNkR5RGDK0vJHnl0Yw6/Mp6cms3JMPPGHZ5Jut24QmQwFMdMn4A6VZk OXlQ== X-Gm-Message-State: AOAM532IOgTwaKEm9W4MSb5sTNdoFlx14N3uxF1Gr0HpVK9i0wy++M0i PUXIMGOTtkv0ksFYX+dh4J0= X-Google-Smtp-Source: ABdhPJw7PJfpxXjaxM6+ou8m8BPWeNrRx1W+DAFZoYct+WXm2enQNXeOEAuj7aPDIPSrcF1LFeoGNA== X-Received: by 2002:a05:6402:657:: with SMTP id u23mr6798799edx.225.1621540959751; Thu, 20 May 2021 13:02:39 -0700 (PDT) Received: from localhost.localdomain ([188.26.52.84]) by smtp.gmail.com with ESMTPSA id y10sm1974288ejh.105.2021.05.20.13.02.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 20 May 2021 13:02:39 -0700 (PDT) From: Vladimir Oltean To: Jakub Kicinski , "David S. Miller" , netdev@vger.kernel.org Cc: Florian Fainelli , Andrew Lunn , Vivien Didelot , Mark Brown , linux-spi@vger.kernel.org, Guenter Roeck , Vladimir Oltean Subject: [PATCH v2 net-next 1/2] net: dsa: sja1105: send multiple spi_messages instead of using cs_change Date: Thu, 20 May 2021 23:02:22 +0300 Message-Id: <20210520200223.3375421-2-olteanv@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210520200223.3375421-1-olteanv@gmail.com> References: <20210520200223.3375421-1-olteanv@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-spi@vger.kernel.org From: Vladimir Oltean The sja1105 driver has been described by Mark Brown as "not using the [ SPI ] API at all idiomatically" due to the use of cs_change: https://patchwork.kernel.org/project/netdevbpf/patch/20210520135031.2969183-1-olteanv@gmail.com/ According to include/linux/spi/spi.h, the chip select is supposed to be asserted for the entire length of a SPI message, as long as cs_change is false for all member transfers. The cs_change flag changes the following: (i) When a non-final SPI transfer has cs_change = true, the chip select should temporarily deassert and then reassert starting with the next transfer. (ii) When a final SPI transfer has cs_change = true, the chip select should remain asserted until the following SPI message. The sja1105 driver only uses cs_change for its first property, to form a single SPI message whose layout can be seen below: this is an entire, single spi_message _______________________________________________________________________________________________ / \ +-------------+---------------+-------------+---------------+ ... +-------------+---------------+ | hdr_xfer[0] | chunk_xfer[0] | hdr_xfer[1] | chunk_xfer[1] | | hdr_xfer[n] | chunk_xfer[n] | +-------------+---------------+-------------+---------------+ ... +-------------+---------------+ cs_change false true false true false false ____________________________ _____________________________ _____________________________ CS line __/ \/ \ ... / \__ The fact of the matter is that spi_max_message_size() has an ambiguous meaning if any non-final transfer has cs_change = true. If the SPI master has a limitation in that it cannot keep the chip select asserted for more than, say, 200 bytes (like the spi-sc18is602), the normal thing for it to do is to implement .max_transfer_size and .max_message_size, and limit both to 200: in the "worst case" where cs_change is always false, then the controller can, indeed, not send messages larger than 200 bytes. But the fact that the SPI controller's max_message_size does not necessarily mean that we cannot send messages larger than that. Notably, if the SPI master special-cases the transfers with cs_change and treats every chip select toggling as an entirely new transaction, then a SPI message can easily exceed that limit. So there is a temptation to ignore the controller's reported max_message_size when using cs_change = true in non-final transfers. But that can lead to false conclusions. As Mark points out, the SPI controller might have a different kind of limitation with the max message size, that has nothing at all to do with how long it can keep the chip select asserted. For example, that might be the case if the device is able to offload the chip select changes to the hardware as part of the data stream, and it packs the entire stream of commands+data (corresponding to a SPI message) into a single DMA transfer that is itself limited in size. So the only thing we can do is avoid ambiguity by not using cs_change at all. Instead of sending a single spi_message, we now send multiple SPI messages as follows: spi_message 0 spi_message 1 spi_message n ____________________________ ___________________________ _____________________________ / \ / \ / \ +-------------+---------------+-------------+---------------+ ... +-------------+---------------+ | hdr_xfer[0] | chunk_xfer[0] | hdr_xfer[1] | chunk_xfer[1] | | hdr_xfer[n] | chunk_xfer[n] | +-------------+---------------+-------------+---------------+ ... +-------------+---------------+ cs_change false true false true false false ____________________________ _____________________________ _____________________________ CS line __/ \/ \ ... / \__ which is clearer because the max_message_size limit is now easier to enforce. What is transmitted on the wire stays, of course, the same. Additionally, because we send no more than 2 transfers at a time, we now avoid dynamic memory allocation too, which might be seen as an improvement by some. Signed-off-by: Vladimir Oltean --- drivers/net/dsa/sja1105/sja1105_spi.c | 52 +++++++-------------------- 1 file changed, 12 insertions(+), 40 deletions(-) diff --git a/drivers/net/dsa/sja1105/sja1105_spi.c b/drivers/net/dsa/sja1105/sja1105_spi.c index f7a1514f81e8..8746e3f158a0 100644 --- a/drivers/net/dsa/sja1105/sja1105_spi.c +++ b/drivers/net/dsa/sja1105/sja1105_spi.c @@ -29,13 +29,6 @@ sja1105_spi_message_pack(void *buf, const struct sja1105_spi_message *msg) sja1105_pack(buf, &msg->address, 24, 4, size); } -#define sja1105_hdr_xfer(xfers, chunk) \ - ((xfers) + 2 * (chunk)) -#define sja1105_chunk_xfer(xfers, chunk) \ - ((xfers) + 2 * (chunk) + 1) -#define sja1105_hdr_buf(hdr_bufs, chunk) \ - ((hdr_bufs) + (chunk) * SJA1105_SIZE_SPI_MSG_HEADER) - /* If @rw is: * - SPI_WRITE: creates and sends an SPI write message at absolute * address reg_addr, taking @len bytes from *buf @@ -46,41 +39,25 @@ static int sja1105_xfer(const struct sja1105_private *priv, sja1105_spi_rw_mode_t rw, u64 reg_addr, u8 *buf, size_t len, struct ptp_system_timestamp *ptp_sts) { + u8 hdr_buf[SJA1105_SIZE_SPI_MSG_HEADER] = {0}; struct sja1105_chunk chunk = { .len = min_t(size_t, len, SJA1105_SIZE_SPI_MSG_MAXLEN), .reg_addr = reg_addr, .buf = buf, }; struct spi_device *spi = priv->spidev; - struct spi_transfer *xfers; + struct spi_transfer xfers[2] = {0}; + struct spi_transfer *chunk_xfer; + struct spi_transfer *hdr_xfer; int num_chunks; int rc, i = 0; - u8 *hdr_bufs; num_chunks = DIV_ROUND_UP(len, SJA1105_SIZE_SPI_MSG_MAXLEN); - /* One transfer for each message header, one for each message - * payload (chunk). - */ - xfers = kcalloc(2 * num_chunks, sizeof(struct spi_transfer), - GFP_KERNEL); - if (!xfers) - return -ENOMEM; - - /* Packed buffers for the num_chunks SPI message headers, - * stored as a contiguous array - */ - hdr_bufs = kcalloc(num_chunks, SJA1105_SIZE_SPI_MSG_HEADER, - GFP_KERNEL); - if (!hdr_bufs) { - kfree(xfers); - return -ENOMEM; - } + hdr_xfer = &xfers[0]; + chunk_xfer = &xfers[1]; for (i = 0; i < num_chunks; i++) { - struct spi_transfer *chunk_xfer = sja1105_chunk_xfer(xfers, i); - struct spi_transfer *hdr_xfer = sja1105_hdr_xfer(xfers, i); - u8 *hdr_buf = sja1105_hdr_buf(hdr_bufs, i); struct spi_transfer *ptp_sts_xfer; struct sja1105_spi_message msg; @@ -129,19 +106,14 @@ static int sja1105_xfer(const struct sja1105_private *priv, chunk.len = min_t(size_t, (ptrdiff_t)(buf + len - chunk.buf), SJA1105_SIZE_SPI_MSG_MAXLEN); - /* De-assert the chip select after each chunk. */ - if (chunk.len) - chunk_xfer->cs_change = 1; + rc = spi_sync_transfer(spi, xfers, 2); + if (rc < 0) { + dev_err(&spi->dev, "SPI transfer failed: %d\n", rc); + return rc; + } } - rc = spi_sync_transfer(spi, xfers, 2 * num_chunks); - if (rc < 0) - dev_err(&spi->dev, "SPI transfer failed: %d\n", rc); - - kfree(hdr_bufs); - kfree(xfers); - - return rc; + return 0; } int sja1105_xfer_buf(const struct sja1105_private *priv, From patchwork Thu May 20 20:02:23 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vladimir Oltean X-Patchwork-Id: 445074 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1588CC43460 for ; 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Thu, 20 May 2021 13:02:40 -0700 (PDT) Received: from localhost.localdomain ([188.26.52.84]) by smtp.gmail.com with ESMTPSA id y10sm1974288ejh.105.2021.05.20.13.02.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 20 May 2021 13:02:40 -0700 (PDT) From: Vladimir Oltean To: Jakub Kicinski , "David S. Miller" , netdev@vger.kernel.org Cc: Florian Fainelli , Andrew Lunn , Vivien Didelot , Mark Brown , linux-spi@vger.kernel.org, Guenter Roeck , Vladimir Oltean Subject: [PATCH v2 net-next 2/2] net: dsa: sja1105: adapt to a SPI controller with a limited max transfer size Date: Thu, 20 May 2021 23:02:23 +0300 Message-Id: <20210520200223.3375421-3-olteanv@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210520200223.3375421-1-olteanv@gmail.com> References: <20210520200223.3375421-1-olteanv@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-spi@vger.kernel.org From: Vladimir Oltean The static config of the sja1105 switch is a long stream of bytes which is programmed to the hardware in chunks (portions with the chip select continuously asserted) of max 256 bytes each. Only that certain SPI controllers, such as the spi-sc18is602 I2C-to-SPI bridge, cannot keep the chip select asserted for that long. The spi_max_transfer_size() and spi_max_message_size() functions are how the controller can impose its hardware limitations upon the SPI peripheral driver. The sja1105 sends its static config to the SPI master in chunks, and each chunk is a spi_message composed of 2 spi_transfers: the buffer with the data and a preceding buffer with the SPI access header. Both buffers must be smaller than the transfer limit, and their sum must be smaller than the message limit. Regression-tested on a switch connected to a controller with no limitations (spi-fsl-dspi) as well as with one with caps for both max_transfer_size and max_message_size (spi-sc18is602). Signed-off-by: Vladimir Oltean --- drivers/net/dsa/sja1105/sja1105_spi.c | 30 ++++++++++++++++++++------- 1 file changed, 23 insertions(+), 7 deletions(-) diff --git a/drivers/net/dsa/sja1105/sja1105_spi.c b/drivers/net/dsa/sja1105/sja1105_spi.c index 8746e3f158a0..7bcf2e419037 100644 --- a/drivers/net/dsa/sja1105/sja1105_spi.c +++ b/drivers/net/dsa/sja1105/sja1105_spi.c @@ -40,19 +40,35 @@ static int sja1105_xfer(const struct sja1105_private *priv, size_t len, struct ptp_system_timestamp *ptp_sts) { u8 hdr_buf[SJA1105_SIZE_SPI_MSG_HEADER] = {0}; - struct sja1105_chunk chunk = { - .len = min_t(size_t, len, SJA1105_SIZE_SPI_MSG_MAXLEN), - .reg_addr = reg_addr, - .buf = buf, - }; struct spi_device *spi = priv->spidev; struct spi_transfer xfers[2] = {0}; struct spi_transfer *chunk_xfer; struct spi_transfer *hdr_xfer; + struct sja1105_chunk chunk; + ssize_t xfer_len; int num_chunks; int rc, i = 0; - num_chunks = DIV_ROUND_UP(len, SJA1105_SIZE_SPI_MSG_MAXLEN); + /* One spi_message is composed of two spi_transfers: a small one for + * the message header and another one for the current chunk of the + * packed buffer. + * Check that the restrictions imposed by the SPI controller are + * respected: the chunk buffer is smaller than the max transfer size, + * and the total length of the chunk plus its message header is smaller + * than the max message size. + */ + xfer_len = min_t(ssize_t, SJA1105_SIZE_SPI_MSG_MAXLEN, + spi_max_transfer_size(spi)); + xfer_len = min_t(ssize_t, SJA1105_SIZE_SPI_MSG_MAXLEN, + spi_max_message_size(spi) - SJA1105_SIZE_SPI_MSG_HEADER); + if (xfer_len < 0) + return -ERANGE; + + num_chunks = DIV_ROUND_UP(len, xfer_len); + + chunk.reg_addr = reg_addr; + chunk.buf = buf; + chunk.len = min_t(size_t, len, xfer_len); hdr_xfer = &xfers[0]; chunk_xfer = &xfers[1]; @@ -104,7 +120,7 @@ static int sja1105_xfer(const struct sja1105_private *priv, chunk.buf += chunk.len; chunk.reg_addr += chunk.len / 4; chunk.len = min_t(size_t, (ptrdiff_t)(buf + len - chunk.buf), - SJA1105_SIZE_SPI_MSG_MAXLEN); + xfer_len); rc = spi_sync_transfer(spi, xfers, 2); if (rc < 0) {