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Mon, 20 Apr 2026 05:42:31 -0700 (PDT) Message-ID: <5f495c4d-60b6-47c5-b84a-e1ad952f1c75@tuxon.dev> Date: Mon, 20 Apr 2026 15:42:29 +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: sashiko.dev review (Re: [PATCH v4 11/17] dmaengine: sh: rz-dmac: Refactor pause/resume code) To: vkoul@kernel.org, Frank.Li@kernel.org, lgirdwood@gmail.com, broonie@kernel.org, perex@perex.cz, tiwai@suse.com, biju.das.jz@bp.renesas.com, prabhakar.mahadev-lad.rj@bp.renesas.com, p.zabel@pengutronix.de, geert+renesas@glider.be, fabrizio.castro.jz@renesas.com, long.luu.ur@renesas.com 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> <20260411114303.2814115-12-claudiu.beznea.uj@bp.renesas.com> Content-Language: en-US From: Claudiu Beznea In-Reply-To: <20260411114303.2814115-12-claudiu.beznea.uj@bp.renesas.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit > commit c08d50f3400ecf3dbc032455be7a589baf899258 > Author: Claudiu Beznea > dmaengine: sh: rz-dmac: Refactor pause/resume code > This commit refactors the pause/resume support to use a bitmask for the > channel status. This prepares the driver for upcoming system suspend and > cyclic DMA support where multiple independent pause states might be active. > > diff --git a/drivers/dma/sh/rz-dmac.c b/drivers/dma/sh/rz-dmac.c > > index 04eb1a7f1e627..d009b7607d447 100644 > > --- a/drivers/dma/sh/rz-dmac.c > > +++ b/drivers/dma/sh/rz-dmac.c > [ ... ] > > +static int rz_dmac_device_resume_set(struct rz_dmac_chan *channel, > > + unsigned long clear_bitmask) > > +{ > > + int ret = 0; > > + u32 val; > > + > > + lockdep_assert_held(&channel->vc.lock); > > + > > + /* Do not check CHSTAT_SUS but rely on HW capabilities. */ > > + > > + rz_dmac_ch_writel(channel, CHCTRL_CLRSUS, CHCTRL, 1); > > + ret = read_poll_timeout_atomic(rz_dmac_ch_readl, val, > > + !(val & CHSTAT_SUS), 1, 1024, false, > > + channel, CHSTAT, 1); > > + > > + channel->status &= ~clear_bitmask; > > + > > + return ret; > > +} > If multiple pause bits are set in channel->status, will this unconditionally > resume the hardware? > If a channel is paused explicitly by a dmaengine client using > RZ_DMAC_CHAN_STATUS_PAUSED, and is subsequently paused by the upcoming system > suspend functionality, The upcomming system suspend functionality don't call rz_dmac_device_pause_set() if RZ_DMAC_CHAN_STATUS_PAUSED is set or the channel is not enabled(), it just return. The following could be checked: static int rz_dmac_device_pause_internal(struct rz_dmac_chan *channel) { lockdep_assert_held(&channel->vc.lock); /* Skip channels explicitly paused by consummers or disabled. */ if (channel->status & BIT(RZ_DMAC_CHAN_STATUS_PAUSED) || !rz_dmac_chan_is_enabled(channel)) return 0; return rz_dmac_device_pause_set(channel, BIT(RZ_DMAC_CHAN_STATUS_PAUSED_INTERNAL)); } > it appears this code will write CHCTRL_CLRSUS to the > hardware as soon as the first of those conditions is cleared. > This would silently override the other pause request, causing the hardware to > resume prematurely while another client expects it to be paused. > Should this update channel->status first, and only write CHCTRL_CLRSUS > to the hardware if no other pause bits remain active (channel->status == 0)?