Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <1591697830-16311-1-git-send-email-amittomer25@gmail.com>
 <1591697830-16311-3-git-send-email-amittomer25@gmail.com> <20200624061529.GF2324254@vkoul-mobl>
 <75d154d0-2962-99e6-a7c7-bf0928ec8b2a@arm.com>
In-Reply-To: <75d154d0-2962-99e6-a7c7-bf0928ec8b2a@arm.com>
From:   Amit Tomer <amittomer25@gmail.com>
Date:   Mon, 29 Jun 2020 13:58:31 +0530
Message-ID: <CABHD4K-uFzzHLcH8SXGYkn_ZburG-g0f-ECrefU2V61Fp+z3fQ@mail.gmail.com>
Subject: Re: [PATCH v4 02/10] dmaengine: Actions: Add support for S700 DMA engine
To:     =?UTF-8?Q?Andr=C3=A9_Przywara?= <andre.przywara@arm.com>
Cc:     Vinod Koul <vkoul@kernel.org>,
        =?UTF-8?Q?Andreas_F=C3=A4rber?= <afaerber@suse.de>,
        Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
        dan.j.williams@intel.com, cristian.ciocaltea@gmail.com,
        dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        linux-actions@lists.infradead.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hi,

On Wed, Jun 24, 2020 at 3:06 PM Andr=C3=A9 Przywara <andre.przywara@arm.com=
> wrote:
>
> On 24/06/2020 07:15, Vinod Koul wrote:
>
> Hi,
>
> > On 09-06-20, 15:47, Amit Singh Tomar wrote:
> >
> >> @@ -372,6 +383,7 @@ static inline int owl_dma_cfg_lli(struct owl_dma_v=
chan *vchan,
> >>                                struct dma_slave_config *sconfig,
> >>                                bool is_cyclic)
> >>  {
> >> +    struct owl_dma *od =3D to_owl_dma(vchan->vc.chan.device);
> >>      u32 mode, ctrlb;
> >>
> >>      mode =3D OWL_DMA_MODE_PW(0);
> >> @@ -427,14 +439,26 @@ static inline int owl_dma_cfg_lli(struct owl_dma=
_vchan *vchan,
> >>      lli->hw[OWL_DMADESC_DADDR] =3D dst;
> >>      lli->hw[OWL_DMADESC_SRC_STRIDE] =3D 0;
> >>      lli->hw[OWL_DMADESC_DST_STRIDE] =3D 0;
> >> -    /*
> >> -     * Word starts from offset 0xC is shared between frame length
> >> -     * (max frame length is 1MB) and frame count, where first 20
> >> -     * bits are for frame length and rest of 12 bits are for frame
> >> -     * count.
> >> -     */
> >> -    lli->hw[OWL_DMADESC_FLEN] =3D len | FCNT_VAL << 20;
> >> -    lli->hw[OWL_DMADESC_CTRLB] =3D ctrlb;
> >> +
> >> +    if (od->devid =3D=3D S700_DMA) {
> >> +            /* Max frame length is 1MB */
> >> +            lli->hw[OWL_DMADESC_FLEN] =3D len;
> >> +            /*
> >> +             * On S700, word starts from offset 0x1C is shared betwee=
n
> >> +             * frame count and ctrlb, where first 12 bits are for fra=
me
> >> +             * count and rest of 20 bits are for ctrlb.
> >> +             */
> >> +            lli->hw[OWL_DMADESC_CTRLB] =3D FCNT_VAL | ctrlb;
> >> +    } else {
> >> +            /*
> >> +             * On S900, word starts from offset 0xC is shared between
> >> +             * frame length (max frame length is 1MB) and frame count=
,
> >> +             * where first 20 bits are for frame length and rest of
> >> +             * 12 bits are for frame count.
> >> +             */
> >> +            lli->hw[OWL_DMADESC_FLEN] =3D len | FCNT_VAL << 20;
> >> +            lli->hw[OWL_DMADESC_CTRLB] =3D ctrlb;
> >
> > Unfortunately this wont scale, we will keep adding new conditions for
> > newer SoC's! So rather than this why not encode max frame length in
> > driver_data rather than S900_DMA/S700_DMA.. In future one can add value=
s
> > for newer SoC and not code above logic again.
>
> What newer SoCs? I don't think we should try to guess the future here.
> We can always introduce further abstractions later, once we actually
> *know* what we are looking at.
>
Apart from it , we have *one* more SoC from Actions .i.e. S500 where
the DMA controller is
identical to S900, and requires *no* additional code to work properly.

So, I think we are safe to have the changes proposed in this patch.

Thanks

-Amit