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 D07C9DDDC for ; Fri, 17 Nov 2023 08:07:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="OriicWON" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BA21AC433C8; Fri, 17 Nov 2023 08:07:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1700208434; bh=8mPk0+JYm3DQ/U1OTjZqnq0hA5XUiluL2NaSKKnbAJU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=OriicWONuG8ZI22bAM9PCopeJt/Z9pIhW1mOi/bs1Dt1V7534fiCKWT/uAJQKnxv6 o20fTzhj7ro3gXNxZxV5913jOUQGvWe+iAL2I6IcXlw8GyjyJmL458pxG3BkAGR+wN +yng31p5VYm1wweQ8QTOFi//29G3IPyUEPP/eKz6mXIpAiG+keEpA7yhTKI40kN8p5 dqfI1HrWOygp1iDSIwleHGMsCJ7LswnKNDkoVRmVy/b91ONEo6XtSdq7Djo5OcVVrg iRhYwFZT57GQb6CmK561NK3/TKPBYG1niWSxndq361GKJpTQLXPIOVlDxf5thCHMCu XBGyvBUIkj9Gw== Date: Fri, 17 Nov 2023 13:37:08 +0530 From: Manivannan Sadhasivam To: Kory Maincent Cc: Gustavo Pimentel , Serge Semin , Vinod Koul , Cai Huoqing , Thomas Petazzoni , dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org, Herve Codina Subject: Re: [PATCH v5 5/6] dmaengine: dw-edma: HDMA: Add sync read before starting the DMA transfer in remote setup Message-ID: <20231117080708.GD10361@thinkpad> References: <20231114-b4-feature_hdma_mainline-v5-0-7bc86d83c6f7@bootlin.com> <20231114-b4-feature_hdma_mainline-v5-5-7bc86d83c6f7@bootlin.com> Precedence: bulk X-Mailing-List: dmaengine@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20231114-b4-feature_hdma_mainline-v5-5-7bc86d83c6f7@bootlin.com> On Tue, Nov 14, 2023 at 03:51:58PM +0100, Kory Maincent wrote: > The Linked list element and pointer are not stored in the same memory as > the HDMA controller register. If the doorbell register is toggled before > the full write of the linked list a race condition error will occur. > In remote setup we can only use a readl to the memory to assure the full > write has occurred. > > Fixes: e74c39573d35 ("dmaengine: dw-edma: Add support for native HDMA") > Reviewed-by: Serge Semin > Signed-off-by: Kory Maincent Few nitpicks below. With those addressed, Reviewed-by: Manivannan Sadhasivam > --- > > Changes in v2: > - Move the sync read in a function. > - Add commments > > Changes in v4: > - Update git commit message. > --- > drivers/dma/dw-edma/dw-hdma-v0-core.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/drivers/dma/dw-edma/dw-hdma-v0-core.c b/drivers/dma/dw-edma/dw-hdma-v0-core.c > index 04b0bcb6ded9..13b6aec6a6de 100644 > --- a/drivers/dma/dw-edma/dw-hdma-v0-core.c > +++ b/drivers/dma/dw-edma/dw-hdma-v0-core.c > @@ -222,6 +222,20 @@ static void dw_hdma_v0_core_write_chunk(struct dw_edma_chunk *chunk) > dw_hdma_v0_write_ll_link(chunk, i, control, chunk->ll_region.paddr); > } > > +static void dw_hdma_v0_sync_ll_data(struct dw_edma_chunk *chunk) > +{ > + /* > + * In case of remote HDMA engine setup, the DW PCIe RP/EP internals s/internals/internal > + * configuration registers and Application memory are normally accessed s/Application/application > + * over different buses. Ensure LL-data reaches the memory before the > + * doorbell register is toggled by issuing the dummy-read from the remote > + * LL memory in a hope that the posted MRd TLP will return only after the MRd TLP is not posted. - Mani > + * last MWr TLP is completed > + */ > + if (!(chunk->chan->dw->chip->flags & DW_EDMA_CHIP_LOCAL)) > + readl(chunk->ll_region.vaddr.io); > +} > + > static void dw_hdma_v0_core_start(struct dw_edma_chunk *chunk, bool first) > { > struct dw_edma_chan *chan = chunk->chan; > @@ -252,6 +266,9 @@ static void dw_hdma_v0_core_start(struct dw_edma_chunk *chunk, bool first) > /* Set consumer cycle */ > SET_CH_32(dw, chan->dir, chan->id, cycle_sync, > HDMA_V0_CONSUMER_CYCLE_STAT | HDMA_V0_CONSUMER_CYCLE_BIT); > + > + dw_hdma_v0_sync_ll_data(chunk); > + > /* Doorbell */ > SET_CH_32(dw, chan->dir, chan->id, doorbell, HDMA_V0_DOORBELL_START); > } > > -- > 2.25.1 > -- மணிவண்ணன் சதாசிவம்