linux-kernel - Re: [PATCH 5/7] dmaengine: sh: rz-dmac: Add suspend to RAM support

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Message-ID: <5438ccc8-ed5a-4dd6-8995-e8e9926883a5@tuxon.dev>
Date: Mon, 26 Jan 2026 14:39:03 +0200
From: Claudiu Beznea <claudiu.beznea@...on.dev>
To: Biju Das <biju.das.jz@...renesas.com>, "vkoul@...nel.org"
 <vkoul@...nel.org>,
 Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@...renesas.com>,
 "lgirdwood@...il.com" <lgirdwood@...il.com>,
 "broonie@...nel.org" <broonie@...nel.org>, "perex@...ex.cz"
 <perex@...ex.cz>, "tiwai@...e.com" <tiwai@...e.com>,
 "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
 "geert+renesas@...der.be" <geert+renesas@...der.be>,
 Fabrizio Castro <fabrizio.castro.jz@...esas.com>
Cc: "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "linux-sound@...r.kernel.org" <linux-sound@...r.kernel.org>,
 "linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>,
 Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH 5/7] dmaengine: sh: rz-dmac: Add suspend to RAM support



On 1/26/26 14:10, Biju Das wrote:
> 
> 
>> -----Original Message-----
>> From: Claudiu Beznea <claudiu.beznea@...on.dev>
>> Sent: 26 January 2026 12:05
>> To: Biju Das <biju.das.jz@...renesas.com>; vkoul@...nel.org; Prabhakar Mahadev Lad <prabhakar.mahadev-
>> lad.rj@...renesas.com>; lgirdwood@...il.com; broonie@...nel.org; perex@...ex.cz; tiwai@...e.com;
>> p.zabel@...gutronix.de; geert+renesas@...der.be; Fabrizio Castro <fabrizio.castro.jz@...esas.com>
>> Cc: dmaengine@...r.kernel.org; linux-kernel@...r.kernel.org; linux-sound@...r.kernel.org; linux-
>> renesas-soc@...r.kernel.org; Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>> Subject: Re: [PATCH 5/7] dmaengine: sh: rz-dmac: Add suspend to RAM support
>>
>> Hi,
>>
>> On 1/26/26 13:03, Biju Das wrote:
>>> Hi Claudiu,
>>>
>>> Thanks for the patch.
>>>
>>>> -----Original Message-----
>>>> From: Claudiu <claudiu.beznea@...on.dev>
>>>> Sent: 26 January 2026 10:32
>>>> Subject: [PATCH 5/7] dmaengine: sh: rz-dmac: Add suspend to RAM
>>>> support
>>>>
>>>> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>>>
>>>> The Renesas RZ/G3S SoC supports a power saving mode in which power to
>>>> most SoC components is turned off, including the DMA IP. Add suspend to RAM support to save and
>> restore the DMA IP registers.
>>>>
>>>> Cyclic DMA channels require special handling. Since they can be
>>>> paused and resumed during system suspend and resume, the driver
>>>> restores additional registers for these channels during the resume
>>>> phase. If a channel was not explicitly paused during suspend, the
>>>> driver ensures that it is paused and resumed as part of the system suspend/resume flow. This might
>> be the case of a serial device being used with no_console_suspend.
>>>>
>>>> For non-cyclic channels, the dev_pm_ops::prepare callback waits for
>>>> all ongoing transfers to complete before allowing suspend-to-RAM to proceed.
>>>>
>>>> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>>> ---
>>>>    drivers/dma/sh/rz-dmac.c | 183 +++++++++++++++++++++++++++++++++++++--
>>>>    1 file changed, 175 insertions(+), 8 deletions(-)
>>>>
>>>> diff --git a/drivers/dma/sh/rz-dmac.c b/drivers/dma/sh/rz-dmac.c
>>>> index ab5f49a0b9f2..8f3e2719e639
>>>> +
>>>> +	pm_runtime_put_sync(dmac->dev);
>>>> +
>>>> +	ret = reset_control_assert(dmac->rstc);
>>>> +	if (ret) {
>>>> +		pm_runtime_resume_and_get(dmac->dev);
>>>> +		rz_dmac_suspend_recover(dmac);
>>>> +	}
>>>> +
>>>
>>>
>>> This patch breaks, s2idle in RZ/G3L as it turns off DMA ACLK and IRQ's
>>> are not routed to CPU for wakeup.
>>
>> Is this particular patch the one that explicitly breaks it? Is there any mainline PM support available
>> for RZ/G3L? Can it be fixed along with the RZ/G3L support, if any, as I don't have the board to test
>> it?
> 
> Maybe your TF-A is enabling DMAACLK during resume. Can you check that mean time, I will check what you have mentioned
> Here?
> 

You used "freeze" in your example. Same did I to check your usecase. That 
suspend type don't involve TF-A (unless something changes and I'm not aware of).

Thank you,
Claudiu