linux-kernel - Re: [PATCH v15 2/4] dmaengine: tegra: Add tegra gpcdma driver

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Date:   Thu, 16 Dec 2021 20:42:28 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Akhil R <akhilrajeev@...dia.com>, dan.j.williams@...el.com,
        devicetree@...r.kernel.org, dmaengine@...r.kernel.org,
        jonathanh@...dia.com, kyarlagadda@...dia.com, ldewangan@...dia.com,
        linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org,
        p.zabel@...gutronix.de, rgumasta@...dia.com, robh+dt@...nel.org,
        thierry.reding@...il.com, vkoul@...nel.org
Cc:     Pavan Kunapuli <pkunapuli@...dia.com>
Subject: Re: [PATCH v15 2/4] dmaengine: tegra: Add tegra gpcdma driver

16.12.2021 20:11, Akhil R пишет:
> +static int tegra_dma_terminate_all(struct dma_chan *dc)
> +{
> +	struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
> +	unsigned long wcount = 0;
> +	unsigned long status;
> +	unsigned long flags;
> +	int err;
> +
> +	raw_spin_lock_irqsave(&tdc->lock, flags);
> +
> +	if (!tdc->dma_desc) {
> +		raw_spin_unlock_irqrestore(&tdc->lock, flags);
> +		return 0;
> +	}
> +
> +	if (!tdc->busy)
> +		goto skip_dma_stop;
> +
> +	if (tdc->tdma->chip_data->hw_support_pause)
> +		err = tegra_dma_pause(tdc);
> +	else
> +		err = tegra_dma_stop_client(tdc);
> +
> +	if (err) {
> +		raw_spin_unlock_irqrestore(&tdc->lock, flags);
> +		return err;
> +	}
> +
> +	status = tdc_read(tdc, TEGRA_GPCDMA_CHAN_STATUS);
> +	if (status & TEGRA_GPCDMA_STATUS_ISE_EOC) {
> +		dev_dbg(tdc2dev(tdc), "%s():handling isr\n", __func__);
> +		tegra_dma_xfer_complete(tdc);
> +		status = tdc_read(tdc, TEGRA_GPCDMA_CHAN_STATUS);
> +	}
> +
> +	wcount = tdc_read(tdc, TEGRA_GPCDMA_CHAN_XFER_COUNT);
> +	tegra_dma_stop(tdc);
> +
> +	tdc->dma_desc->bytes_transferred +=
> +			tdc->dma_desc->bytes_requested - (wcount * 4);
> +
> +skip_dma_stop:
> +	tegra_dma_sid_free(tdc);
> +	vchan_free_chan_resources(&tdc->vc);
> +	kfree(&tdc->vc);

You really going to kfree the head of tegra_dma_channel here? Once
again, this code was 100% untested :/

You're not allowed to free channel from the dma_terminate_all()
callback. This callback terminates submitted descs, that's it.

https://elixir.bootlin.com/linux/v5.16-rc5/source/include/linux/dmaengine.h#L1105

https://elixir.bootlin.com/linux/v5.16-rc5/source/drivers/i2c/busses/i2c-tegra.c#L962