linux-kernel - Re: [PATCH 06/14] dmaengine: dma-jz4780: Add support for the JZ4725B SoC

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Message-Id: <1531237502.17118.3@crapouillou.net>
Date:   Tue, 10 Jul 2018 17:45:02 +0200
From:   Paul Cercueil <paul@...pouillou.net>
To:     Vinod <vkoul@...nel.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        Zubair Lutfullah Kakakhel <Zubair.Kakakhel@...tec.com>,
        Mathieu Malaterre <malat@...ian.org>,
        Daniel Silsby <dansilsby@...il.com>, dmaengine@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mips@...ux-mips.org
Subject: Re: [PATCH 06/14] dmaengine: dma-jz4780: Add support for the JZ4725B
 SoC



Le lun. 9 juil. 2018 à 19:14, Vinod <vkoul@...nel.org> a écrit :
> On 03-07-18, 14:32, Paul Cercueil wrote:
>>  The JZ4725B has one DMA core starring six DMA channels.
>>  As for the JZ4770, each DMA channel's clock can be enabled with
>>  a register write, the difference here being that once started, it
>>  is not possible to turn it off.
> 
> ok so disable for this, right..
> 
>>  @@ -204,6 +205,8 @@ static inline void 
>> jz4780_dma_chan_enable(struct jz4780_dma_dev *jzdma,
>>   {
>>   	if (jzdma->version == ID_JZ4770)
>>   		jz4780_dma_ctrl_writel(jzdma, JZ_DMA_REG_DCKES, BIT(chn));
>>  +	else if (jzdma->version == ID_JZ4725B)
>>  +		jz4780_dma_ctrl_writel(jzdma, JZ_DMA_REG_DCKE, BIT(chn));
> 
> but you are writing to a different register here..

Yes. SoCs >= JZ4770 have the DCKE read-only register, and DCKES/DCKEC 
to set/clear bits in DCKE.
On JZ4725B, DCKE is read/write, but the zeros written are ignored (at 
least that's what the
documentation says).

> --
> ~Vinod

Thanks,
-Paul