linux-kernel - RE: [PATCH v17 2/4] dmaengine: tegra: Add tegra gpcdma driver

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <DM5PR12MB1850D677140466EC74C621A4C0259@DM5PR12MB1850.namprd12.prod.outlook.com>
Date:   Mon, 31 Jan 2022 09:09:21 +0000
From:   Akhil R <akhilrajeev@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>
CC:     "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Krishna Yarlagadda <kyarlagadda@...dia.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        Rajesh Gumasta <rgumasta@...dia.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "thierry.reding@...il.com" <thierry.reding@...il.com>,
        "vkoul@...nel.org" <vkoul@...nel.org>,
        Pavan Kunapuli <pkunapuli@...dia.com>
Subject: RE: [PATCH v17 2/4] dmaengine: tegra: Add tegra gpcdma driver

> В Mon, 31 Jan 2022 04:25:14 +0000
> Akhil R <akhilrajeev@...dia.com> пишет:
> 
> > > 30.01.2022 19:34, Akhil R пишет:
> > > >> 29.01.2022 19:40, Akhil R пишет:
> > > >>> +static int tegra_dma_device_pause(struct dma_chan *dc) {
> > > >>> +     struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
> > > >>> +     unsigned long wcount, flags;
> > > >>> +     int ret = 0;
> > > >>> +
> > > >>> +     if (!tdc->tdma->chip_data->hw_support_pause)
> > > >>> +             return 0;
> > > >>
> > > >> It's wrong to return zero if pause unsupported, please see what
> > > >> dmaengine_pause() returns.
> > > >>
> > > >>> +
> > > >>> +     spin_lock_irqsave(&tdc->vc.lock, flags);
> > > >>> +     if (!tdc->dma_desc)
> > > >>> +             goto out;
> > > >>> +
> > > >>> +     ret = tegra_dma_pause(tdc);
> > > >>> +     if (ret) {
> > > >>> +             dev_err(tdc2dev(tdc), "DMA pause timed out\n");
> > > >>> +             goto out;
> > > >>> +     }
> > > >>> +
> > > >>> +     wcount = tdc_read(tdc, TEGRA_GPCDMA_CHAN_XFER_COUNT);
> > > >>> +     tdc->dma_desc->bytes_xfer +=
> > > >>> +                     tdc->dma_desc->bytes_req - (wcount * 4);
> > > >>
> > > >> Why transfer is accumulated?
> > > >>
> > > >> Why do you need to update xfer size at all on pause?
> > > >
> > > > I will verify the calculation. This looks correct only for single
> > > > sg transaction.
> > > >
> > > > Updating xfer_size is added to support drivers which pause the
> > > > transaction and read the status before terminating.
> > > > Eg.
> > >
> > > Why you couldn't update the status in tegra_dma_terminate_all()?
> > Is it useful to update the status in terminate_all()? I assume the
> > descriptor Is freed in vchan_dma_desc_free_list() or am I getting it
> > wrong?
> 
> Yes, it's not useful. Then you only need to fix the tx_status() and
> don't touch dma_desc on pause.
If the bytes_xfer is updated in tx_status(), I suppose 
DMA_RESIDUE_GRANULARITY_BURST can be kept as is, correct?

Thanks,
Akhil