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Tue, 14 Apr 2026 01:28:16 -0700 (PDT) Message-ID: Date: Tue, 14 Apr 2026 11:28:13 +0300 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 05/17] dmaengine: sh: rz-dmac: Do not disable the channel on error To: Biju Das , "vkoul@kernel.org" , "Frank.Li@kernel.org" , "lgirdwood@gmail.com" , "broonie@kernel.org" , "perex@perex.cz" , "tiwai@suse.com" , Prabhakar Mahadev Lad , "p.zabel@pengutronix.de" , "geert+renesas@glider.be" , Fabrizio Castro , Long Luu Cc: "dmaengine@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-sound@vger.kernel.org" , "linux-renesas-soc@vger.kernel.org" , Claudiu Beznea References: <20260411114303.2814115-1-claudiu.beznea.uj@bp.renesas.com> <20260411114303.2814115-6-claudiu.beznea.uj@bp.renesas.com> Content-Language: en-US From: Claudiu Beznea In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 4/11/26 15:30, Biju Das wrote: > > >> -----Original Message----- >> From: Claudiu >> Sent: 11 April 2026 12:43 > -soc@vger.kernel.org; Claudiu Beznea >> >> Subject: [PATCH v4 05/17] dmaengine: sh: rz-dmac: Do not disable the channel on error >> >> From: Claudiu Beznea >> >> Disabling the channel on error is pointless, as if other transfers are queued, the IRQ thread will be >> woken up and will execute them anyway by calling rz_dmac_xfer_desc(). >> >> rz_dmac_xfer_desc() re-enables the transfer. Before doing so, it sets CHCTRL.SWRST, which clears >> CHSTAT.DER and CHSTAT.END anyway. >> >> Skip disabling the DMA channel and just log the error instead. >> >> Signed-off-by: Claudiu Beznea >> --- >> >> Changes in v4: >> - none >> >> Changes in v3: >> - none, this patch is new >> >> drivers/dma/sh/rz-dmac.c | 4 ---- >> 1 file changed, 4 deletions(-) >> >> diff --git a/drivers/dma/sh/rz-dmac.c b/drivers/dma/sh/rz-dmac.c index 40ddf534c094..943c005f52bd >> 100644 >> --- a/drivers/dma/sh/rz-dmac.c >> +++ b/drivers/dma/sh/rz-dmac.c >> @@ -871,10 +871,6 @@ static void rz_dmac_irq_handle_channel(struct rz_dmac_chan *channel) >> if (chstat & CHSTAT_ER) { >> dev_err(dmac->dev, "DMAC err CHSTAT_%d = %08X\n", >> channel->index, chstat); >> - >> - scoped_guard(spinlock_irqsave, &channel > ->vc.lock) >> - rz_dmac_disable_hw(channel); > > On previous patch, rz_dmac_disable_hw() for initializing each register > > + /* Initialize register for each channel */ > + rz_dmac_disable_hw(channel); This initializes a single register by clearing various bits. > > > As per hardware manual, > > Once an error occurs, the data of the whole transfer cannot be guaranteed. > Be sure to start the transaction again from the > beginning by following the procedure below. > 1. Set 1 in the SWRST bit of the CHCTRL_n/nS register. > 2. Set each register again. I wasn't aware of this sequence. Thank for pointing it. However, calling rz_dmac_disable_hw() as it previously was may be wrong from my point of view. According to the sequence you pointed, I think the code here should have only set the SWRST, if any, and let the rz_dmac_xfer_desc() "set each register again". According to "Figure 14.26 Setting Example 4", of RZ/G3S HW manual, rev 1.20, the registers that need to be set when starting DMAC ch in Link mode are: - DCTRL = 0x1 - NXLA = 0x1000 - CHCFG = 0x80000000 - CHCTRL = 0x8 // swreset - CHCTRL = 0x5 // enable So, I think these are the registers that need to be re-configured again (handled though the rz_dmac_xfer_desc()). Anyway, I'll drop this patch from the next version, as it is not the subject of cyclic DMA. Thank you, Claudiu