From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Yoshihiro Shimoda , Vinod Koul , Sasha Levin Subject: [PATCH 4.18 223/235] dmaengine: sh: rcar-dmac: avoid to write CHCR.TE to 1 if TCR is set to 0 Date: Mon, 24 Sep 2018 13:53:29 +0200 Message-Id: <20180924113125.525792277@linuxfoundation.org> In-Reply-To: <20180924113103.999624566@linuxfoundation.org> References: <20180924113103.999624566@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yoshihiro Shimoda [ Upstream commit 538603c6026ce769eec633bb79349f5f287519c7 ] This patch fixes an issue that unexpected retransfering happens if TCR is set to 0 before rcar_dmac_sync_tcr() writes DE bit to the CHCR register. For example, sh-sci driver can reproduce this issue like below: In rx_timer_fn(): /* CHCR DE bit may be set to 1 */ dmaengine_tx_status() rcar_dmac_tx_status() rcar_dmac_chan_get_residue() rcar_dmac_sync_tcr() /* TCR is possible to be set to 0 */ According to the description of commit 73a47bd0da66 ("dmaengine: rcar-dmac: use TCRB instead of TCR for residue"), "this buffered data will be transferred if CHCR::DE bit was cleared". So, this patch doesn't need to check TCRB register. Fixes: 73a47bd0da66 ("dmaengine: rcar-dmac: use TCRB instead of TCR for residue") Signed-off-by: Yoshihiro Shimoda Signed-off-by: Vinod Koul Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/dma/sh/rcar-dmac.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- a/drivers/dma/sh/rcar-dmac.c +++ b/drivers/dma/sh/rcar-dmac.c @@ -774,8 +774,9 @@ static void rcar_dmac_sync_tcr(struct rc /* make sure all remaining data was flushed */ rcar_dmac_chcr_de_barrier(chan); - /* back DE */ - rcar_dmac_chan_write(chan, RCAR_DMACHCR, chcr); + /* back DE if remain data exists */ + if (rcar_dmac_chan_read(chan, RCAR_DMATCR)) + rcar_dmac_chan_write(chan, RCAR_DMACHCR, chcr); } static void rcar_dmac_chan_halt(struct rcar_dmac_chan *chan)