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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 95D37C5AE59 for ; Thu, 5 Jun 2025 14:15:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To:Subject: MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=fRTTeGsbcaw5c2bpCivhaXyjdw7iXjCjq6xZdnFMGEk=; b=IZWchjImsBAexK wvtIimKteymJx6tRljRfE15dzrQf8Lwn9XehC4V9Ua2HtpfZKdnN3TQ8MFbY3HDENifq80f1MbCwU 3ifBZU23R0mzlORZZlSYHn0Zwd9jSqok5mlO2HCqFePvYDvFVREVP7IekYy+jet268guA7cZEb5wg 5x7f85dqRwOg4qs5wIPIsfH2EKgGi4t9MA5kjGLtXpCw9kAZvM1FXerfwCod8f3Ii8SQ10E5DSed6 I8FAPKj0V/3zKkEmzk80lFyfYEd8+ozuaFvcINrLZb7kYfezOgf5DOShh9vtkmrrM9jjI7Mr8XLcD YcamIIx4oLn8FXbPgNMw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uNBNk-0000000FkT3-1R51; Thu, 05 Jun 2025 14:15:48 +0000 Received: from mgamail.intel.com ([192.198.163.14]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1uNBFb-0000000FjTH-2y0y for linux-i3c@lists.infradead.org; Thu, 05 Jun 2025 14:07:24 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1749132444; x=1780668444; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=fP3E0TPRZPKCsxGV+j+OjJISiSlS2dQrovmKbR7WLsQ=; b=JyCuryWgpygetn4CW4Yrt2t5GRn+PKsKRQRZF0eugg/C6AeBg+e0Sgbq ca4l8elwp1Qy6ZSWDwM97IFuXjkDJNP/OZgg3HHTA1zbIviUyK1wgY6a2 4VcV59AiHmOYeuzrxXiSjNMKoY+4zNc4XsaZj+7nKVIPBXtaE1YKaPE+B DdagQf6pt7kTZMv08EYveYgiL7jRnsfZv0Ch601sLr8/FYDFeqGv+hHmB FYKNO0Ze+oT55+FDeS5mK9u7RZMUPnrmixeoyFzTWOxkZN/13c1wVBRN5 /dU2UAHUxrtZtzgHEzQYQvMlqP3mmwWRXNIC94MoaeGHUiiLlSNA7ISQr A==; X-CSE-ConnectionGUID: 5hK6fYsNTkusZXZtDyJdqQ== X-CSE-MsgGUID: 3UOSudw2RDGYsKvPELFqEw== X-IronPort-AV: E=McAfee;i="6800,10657,11455"; a="51346706" X-IronPort-AV: E=Sophos;i="6.16,212,1744095600"; d="scan'208";a="51346706" Received: from orviesa008.jf.intel.com ([10.64.159.148]) by fmvoesa108.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Jun 2025 07:07:22 -0700 X-CSE-ConnectionGUID: uf/DCkGFTcKHYa4Z4Vo4Vg== X-CSE-MsgGUID: lFQZiyveQD6ephmkDPCEhQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.16,212,1744095600"; d="scan'208";a="146498436" Received: from mylly.fi.intel.com (HELO [10.237.72.50]) ([10.237.72.50]) by orviesa008.jf.intel.com with ESMTP; 05 Jun 2025 07:07:21 -0700 Message-ID: Date: Thu, 5 Jun 2025 17:07:19 +0300 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/3] i3c: mipi-i3c-hci: Make bounce buffer code generic to all DMA transfers To: Frank Li Cc: linux-i3c@lists.infradead.org, Alexandre Belloni References: <20250604125513.1593109-1-jarkko.nikula@linux.intel.com> Content-Language: en-US From: Jarkko Nikula In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250605_070723_799279_979818F9 X-CRM114-Status: GOOD ( 22.23 ) X-BeenThere: linux-i3c@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-i3c" Errors-To: linux-i3c-bounces+linux-i3c=archiver.kernel.org@lists.infradead.org Hi On 6/4/25 6:00 PM, Frank Li wrote: > On Wed, Jun 04, 2025 at 03:55:11PM +0300, Jarkko Nikula wrote: >> Move DMA bounce buffer code for I3C private transfers to be generic for >> all DMA transfers, and round up the receive bounce buffer size to a >> multiple of DWORDs. >> >> It was observed that when the device DMA is IOMMU mapped and the receive >> length is not a multiple of DWORDs, the last DWORD is padded with stale >> data from the RX FIFO, corrupting 1-3 bytes beyond the expected data. >> >> A similar issue, though less severe, occurs when an I3C target returns >> less data than requested. In this case, the padding does not exceed the >> requested number of bytes, assuming the device DMA is not IOMMU mapped. >> >> Therefore, all I3C private transfer, CCC command payload and I2C >> transfer receive buffers must be properly sized for the DMA being IOMMU >> mapped. Even if those buffers are already DMA safe, their size may not >> be, and I don't have a clear idea how to guarantee this other than >> using a local bounce buffer. >> >> To prepare for the device DMA being IOMMU mapped and to address the >> above issue, implement a local, properly sized bounce buffer for all >> DMA transfers. For now, allocate it only when the buffer is in the >> vmalloc() area to avoid unnecessary copying with CCC commands and >> DMA-safe I2C transfers. >> >> Signed-off-by: Jarkko Nikula >> --- >> drivers/i3c/master/mipi-i3c-hci/core.c | 34 ------------------- >> drivers/i3c/master/mipi-i3c-hci/dma.c | 47 +++++++++++++++++++++++++- >> 2 files changed, 46 insertions(+), 35 deletions(-) >> >> diff --git a/drivers/i3c/master/mipi-i3c-hci/core.c b/drivers/i3c/master/mipi-i3c-hci/core.c >> index bc4538694540..24c5e7d5b439 100644 >> --- a/drivers/i3c/master/mipi-i3c-hci/core.c >> +++ b/drivers/i3c/master/mipi-i3c-hci/core.c >> @@ -272,34 +272,6 @@ static int i3c_hci_daa(struct i3c_master_controller *m) >> return hci->cmd->perform_daa(hci); >> } >> > ... >> } >> >> +static void *hci_dma_alloc_safe_xfer_buf(struct i3c_hci *hci, >> + struct hci_xfer *xfer) >> +{ >> + if (!is_vmalloc_addr(xfer->data)) >> + return xfer->data; >> + >> + if (xfer->rnw) >> + /* >> + * Round up the receive bounce buffer length to a multiple of >> + * DWORDs. Independently of buffer alignment, DMA_FROM_DEVICE >> + * transfers may corrupt the last DWORD when transfer length is >> + * not a multiple of DWORDs. This was observed when the device >> + * DMA is IOMMU mapped or when an I3C target device returns >> + * less data than requested. Latter case is less severe and >> + * does not exceed the requested number of bytes, assuming the >> + * device DMA is not IOMMU mapped. >> + */ >> + xfer->bounce_buf = kzalloc(ALIGN(xfer->data_len, 4), >> + GFP_KERNEL); >> + else >> + xfer->bounce_buf = kmemdup(xfer->data, xfer->data_len, >> + GFP_KERNEL); >> + >> + return xfer->bounce_buf; > > Why need use bounce_buf? why not use dma_map_single()?, which will check > alignment and size to decide if use swiotlb as bounce buffer. > We do pass the buffer to the dma_map_single(). I've understood swiotlb is transparently used when the DMA cannot directly access the memory but that's not the case here. -- linux-i3c mailing list linux-i3c@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-i3c