From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 62AB5175A81; Mon, 27 Apr 2026 01:22:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777252958; cv=none; b=XwEqjfzfa2I+IPaxu+/cmxn7cRGSCGuHqFmXQmZG5NGJ/DmngbtI2z+ADWdTgz4Re2MF6RpMbhc+sYa/bEjaiX8ZdkdekCVV2/5qfFn+4H96YJJfOzf8AkyBQHnztDl+1AmGJ9BKyOEkJ2Dkr3gm+iDk1BkU98MZ3kdYCTfDjR4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777252958; c=relaxed/simple; bh=BX2k3FegiT32JzBDbtax9RMlTkcLecybywnZHE8gaZQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ljakW/5d4lBvll4WIUuFv12j7kN4hFORkdIf+DWccc+PzOxYxAcZCSPzTWYiHhfTgh2//+tDa71O0VXSx2QUji8GOqGqL8dUIMt8Qa6TauINOTmgtx4UsQlpVpTIyDIr6C6IgehzPQUchmc43Y4CuC8hRSVi0tboIDS7WbxWfX8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=f0EnkfuD; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="f0EnkfuD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D55B1C2BCAF; Mon, 27 Apr 2026 01:22:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777252958; bh=BX2k3FegiT32JzBDbtax9RMlTkcLecybywnZHE8gaZQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=f0EnkfuDHwk9kVnmr/AtkHvJi+lCHl8Udshb3TzJ784jps1WlWfhmhbKnoLcExi38 VBBnan8jXt0nuoUwCJiO4T/ardJo9M5s2t/XrJ7glnlmfPfna75N15LWsPbVGD5Mzy SSbzS4XG6IFDI1UyMRmNGafYwy2DCuhZM75ZHcj5p4A2T5K9kjy3vfrllKbrRtP67w DCnFuOZ1wfGDF27/9fI+Tepjm3YuzBFIvt35daqI24TP4+3nAozdpFhKoE1Iaj7sEb ADWZfB/Ohcso+uPZGcDkknJk0ZiqrrilMclLDlXa+TEwD2nYo8YrxRYTpdkajqTkC7 bl+uxULiq3a+A== Date: Mon, 27 Apr 2026 09:22:34 +0800 From: "Peter Chen (CIX)" To: Yongchao Wu , pawell@cadence.com Cc: rogerq@kernel.org, gregkh@linuxfoundation.org, linux-usb@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] usb: cdns3: gadget: fix request skipping after clearing halt Message-ID: References: <20260423160601.2949010-1-yongchao.wu@autochips.com> Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260423160601.2949010-1-yongchao.wu@autochips.com> On 26-04-24 00:06:01, Yongchao Wu wrote: > According to the cdns3 datasheet, the EPRST (Endpoint Reset) command > causes the DMA engine to reposition its internal pointer to the next > Transfer Descriptor (TD) if it was already processing one. > > This issue is consistently observed during the ADB identification > process on macOS hosts, where the host issues a Clear_Halt. Although > commit 4bf2dd65135a ("usb: cdns3: gadget: toggle cycle bit before reset > endpoint") attempted to avoid DMA advance by toggling the cycle bit, > trace logs show that on certain hosts like macOS, the DMA pointer > (EP_TRADDR) still shifts after EPRST: > > cdns3_ctrl_req: Clear Endpoint Feature(Halt ep1out) > cdns3_doorbell_epx: ep1out, ep_trbaddr f9c04030 <-- Should be f9c04000 > cdns3_gadget_giveback: ep1out: req: ... length: 16384/16384 > > As shown above, the DMA pointer jumped to index 3 (offset 0x30), causing > the controller to skip the initial TRBs of the request. This leads to > data misalignment and ADB protocol hangs on macOS. Pawel, Is it a hardware issue? The cycle bit has already been toggled before the endpoint has been reset, why the DMA pointer still advances? Peter > > Fix this by manually restoring the EP_TRADDR register to the starting > physical address of the current request after the EPRST operation is > complete. > > Fixes: 7733f6c32e36 ("usb: cdns3: Add Cadence USB3 DRD Driver") > Cc: stable@vger.kernel.org > Cc: Peter Chen > Signed-off-by: Yongchao Wu > --- > drivers/usb/cdns3/cdns3-gadget.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > diff --git a/drivers/usb/cdns3/cdns3-gadget.c b/drivers/usb/cdns3/cdns3-gadget.c > index d59a60a16ec77..96653c7d18f20 100644 > --- a/drivers/usb/cdns3/cdns3-gadget.c > +++ b/drivers/usb/cdns3/cdns3-gadget.c > @@ -2814,9 +2814,19 @@ int __cdns3_gadget_ep_clear_halt(struct cdns3_endpoint *priv_ep) > priv_ep->flags &= ~(EP_STALLED | EP_STALL_PENDING); > > if (request) { > - if (trb) > + if (trb) { > *trb = trb_tmp; > > + /* > + * Per datasheet, EPRST causes DMA to reposition to the next TD. > + * Manually reset EP_TRADDR to the current TRB to prevent > + * the hardware from skipping the interrupted request. > + */ > + writel(EP_TRADDR_TRADDR(priv_ep->trb_pool_dma + > + priv_req->start_trb * TRB_SIZE), > + &priv_dev->regs->ep_traddr); > + } > + > cdns3_rearm_transfer(priv_ep, 1); > } > > > base-commit: 46b513250491a7bfc97d98791dbe6a10bcc8129d > -- > 2.43.0 > > -- Best regards, Peter