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Date: Thu, 23 Sep 2021 14:20:30 +0100 From: Jon Hunter <jonathanh@...dia.com> To: Akhil R <akhilrajeev@...dia.com> CC: "dan.j.williams@...el.com" <dan.j.williams@...el.com>, "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>, 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>, "thierry.reding@...il.com" <thierry.reding@...il.com>, "vkoul@...nel.org" <vkoul@...nel.org>, Pavan Kunapuli <pkunapuli@...dia.com> Subject: Re: [PATCH v6 2/4] dmaengine: tegra: Add tegra gpcdma driver On 23/09/2021 13:51, Akhil R wrote: >> On 22/09/2021 15:46, Akhil R wrote: >>> >>>> On 17/09/2021 15:11, Akhil R wrote: >>>>> +static int tegra_dma_slave_config(struct dma_chan *dc, >>>>> + struct dma_slave_config *sconfig) { >>>>> + struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc); >>>>> + >>>>> + if (tdc->dma_desc) { >>>>> + dev_err(tdc2dev(tdc), "Configuration not allowed\n"); >>>>> + return -EBUSY; >>>>> + } >>>>> + >>>>> + memcpy(&tdc->dma_sconfig, sconfig, sizeof(*sconfig)); >>>>> + if (tdc->slave_id == -1) >>>>> + tdc->slave_id = sconfig->slave_id; >>>>> + >>>>> + tdc->config_init = true; >>>>> + return 0; >>>>> +} >>>> >>>> So you have a function to reserve a slave ID, but you don't check >>>> here if it is already reserved. >>> slave-id is reserved considering the direction as well. >>> 'direction' is available only during prep_slave_sg function, I guess. >> >> Sorry I don't understand what you mean by that. > I mean, it would not be possible to check if the sid is in use without knowing > if the direction is MEM_TO_DEV or DEV_TO_MEM. The bitmask to check the > sid reservation is separate for MEM_TO_DEV and DEV_TO_MEM. > To get the direction parameter, we would need to wait till dma_prep_slave_sg > is called, I guess. I saw in the documentation that the 'direction' element in > dma_slave_config struct is deprecated and should use the value passed to > dma_prep_slave_sg(). Do we even need to worry about slave_id here? Typically the slave_id is coming from device-tree and so is handled by tegra_dma_of_xlate(). I would drop this unless there is an actual use-case we need to support that uses this. Jon -- nvpublic
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