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 A85F9D529 for ; Fri, 17 Nov 2023 08:08:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="cUfA0Pj8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9DA81C433C7; Fri, 17 Nov 2023 08:08:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1700208529; bh=HJEtSlR2M5HLiOxVxrCGWQb4pam62naOtP++t26z2iM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=cUfA0Pj8JG63mQwdDf3sR2/Dn/dhIdm3bHnL5P+aRL89q9qLinL77fiJiTECUxBen Vx5jBSPVYDw/Ey1JmqFOJb93v2oft1VP8bOjHG5Gi4BQklNejRNuopPknmf4kRmlpu JVCKKeysqMFLilK8BmhEXMIUdhJ4PckONU0sB4CnkPP4ew89GZVY76GHPizoBIDPtW 33+Y+xmFZwXaV39BirtxxadqwyKiRGKylIuqXfp56upviS5bdrzQto3IwJiIIA0WO6 QwK6S1rgKwUdcstRLJRdHkkxrcBbkvnVU6gUs3ArjntPZ1ayzET0Q+wgrjyh7ijgp8 l5b3YM0nYBw+A== Date: Fri, 17 Nov 2023 13:38:43 +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 6/6] dmaengine: dw-edma: eDMA: Add sync read before starting the DMA transfer in remote setup Message-ID: <20231117080843.GE10361@thinkpad> References: <20231114-b4-feature_hdma_mainline-v5-0-7bc86d83c6f7@bootlin.com> <20231114-b4-feature_hdma_mainline-v5-6-7bc86d83c6f7@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-v5-6-7bc86d83c6f7@bootlin.com> On Tue, Nov 14, 2023 at 03:51:59PM +0100, Kory Maincent wrote: > The Linked list element and pointer are not stored in the same memory as > the eDMA 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: 7e4b8a4fbe2c ("dmaengine: Add Synopsys eDMA IP version 0 support") > Reviewed-by: Serge Semin Same comment as patch 5/6. With that addressed, Reviewed-by: Manivannan Sadhasivam - Mani > Signed-off-by: Kory Maincent > --- > > Changes in v2: > - New patch > > Changes in v4: > - Update git commit message. > --- > drivers/dma/dw-edma/dw-edma-v0-core.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/drivers/dma/dw-edma/dw-edma-v0-core.c b/drivers/dma/dw-edma/dw-edma-v0-core.c > index b38786f0ad79..6245b720fbfe 100644 > --- a/drivers/dma/dw-edma/dw-edma-v0-core.c > +++ b/drivers/dma/dw-edma/dw-edma-v0-core.c > @@ -346,6 +346,20 @@ static void dw_edma_v0_core_write_chunk(struct dw_edma_chunk *chunk) > dw_edma_v0_write_ll_link(chunk, i, control, chunk->ll_region.paddr); > } > > +static void dw_edma_v0_sync_ll_data(struct dw_edma_chunk *chunk) > +{ > + /* > + * In case of remote eDMA engine setup, the DW PCIe RP/EP internals > + * configuration registers and Application memory are normally accessed > + * 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 > + * last MWr TLP is completed > + */ > + if (!(chunk->chan->dw->chip->flags & DW_EDMA_CHIP_LOCAL)) > + readl(chunk->ll_region.vaddr.io); > +} > + > static void dw_edma_v0_core_start(struct dw_edma_chunk *chunk, bool first) > { > struct dw_edma_chan *chan = chunk->chan; > @@ -412,6 +426,9 @@ static void dw_edma_v0_core_start(struct dw_edma_chunk *chunk, bool first) > SET_CH_32(dw, chan->dir, chan->id, llp.msb, > upper_32_bits(chunk->ll_region.paddr)); > } > + > + dw_edma_v0_sync_ll_data(chunk); > + > /* Doorbell */ > SET_RW_32(dw, chan->dir, doorbell, > FIELD_PREP(EDMA_V0_DOORBELL_CH_MASK, chan->id)); > > -- > 2.25.1 > -- மணிவண்ணன் சதாசிவம்