Message-Id: <AA1C6D16-9016-4A11-9F90-C49A13FACBC0@cutebit.org>
Date:   Thu, 31 Mar 2022 11:42:00 +0200
From:   Martin Povišer <povik@...ebit.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Martin Povišer <povik+lin@...ebit.org>,
        Hector Martin <marcan@...can.st>,
        Sven Peter <sven@...npeter.dev>, Vinod Koul <vkoul@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        linux-arm-kernel@...ts.infradead.org, dmaengine@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mark Kettenis <kettenis@...nbsd.org>
Subject: Re: [PATCH 2/2] dmaengine: apple-admac: Add Apple ADMAC driver


> On 31. 3. 2022, at 8:25, Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:
> 
> On 30/03/2022 18:44, Martin Povišer wrote:
>> Add driver for Audio DMA Controller present on Apple SoCs from the
>> "Apple Silicon" family.
>> 
>> Signed-off-by: Martin Povišer <povik+lin@...ebit.org>
>> ---
>> MAINTAINERS               |   2 +
>> drivers/dma/Kconfig       |   8 +
>> drivers/dma/Makefile      |   1 +
>> drivers/dma/apple-admac.c | 799 ++++++++++++++++++++++++++++++++++++++
>> 4 files changed, 810 insertions(+)
>> create mode 100644 drivers/dma/apple-admac.c
>> 
> 
> (...)
> 
>> +
>> +static void admac_poke(struct admac_data *ad, int reg, u32 val)
>> +{
>> +	writel_relaxed(val, ad->base + reg);
>> +}
>> +
>> +static u32 admac_peek(struct admac_data *ad, int reg)
>> +{
> 
> Please do not write some custom-named functions for common functions. No
> need to "#define true 0" or "#define read peek" etc. Read is read, write
> is write. Using other names is counter intuitive and makes reading the
> code more difficult.
> 
> You actually should not have these wrappers because they don't make the
> code smaller (more arguments needed...).
> 
> If you want the wrappers, please use regmap_mmio.
> 
> Only modify wrapper save some space, so it could stay.

I get the aversion to custom naming, but I would rather keep the helpers.
Compare e.g.

  admac_write(ad, REG_BUS_WIDTH(adchan->no), bus_width);

and

  writel_relaxed(bus_width, ad->base + REG_BUS_WIDTH(adchan->no));

Although I guess as you said I may use regmap.

>> +	return readl_relaxed(ad->base + reg);
>> +}
>> +
>> +static void admac_modify(struct admac_data *ad, int reg, u32 mask, u32 val)
>> +{
>> +	void __iomem *addr = ad->base + reg;
>> +	u32 curr = readl_relaxed(addr);
>> +
>> +	writel_relaxed((curr & ~mask) | (val & mask), addr);
>> +}


>> +
>> +/*
>> + * Write one hardware descriptor for a dmaengine cyclic transaction.
>> + */
>> +static void admac_cyclic_write_one_desc(struct admac_data *ad, int channo,
>> +					struct admac_tx *tx)
>> +{
>> +	dma_addr_t addr;
>> +
>> +	if (WARN_ON(!tx->cyclic))
> 
> WARN_ON_ONCE() - although I wonder why do you need this. You fully
> control the callers to this function, don't you?

I do. Not really needed, just wanted to make it obvious we are operating
under that assumption. Can drop it then.

>> +		return;
>> +
>> +	addr = tx->buf_addr + (tx->submitted_pos % tx->buf_len);
>> +	WARN_ON(addr + tx->period_len > tx->buf_end);
> 
> If this is possible, you have buggy code. If this is not possible, why warn?

Well so if the code is buggy, I will get kicked right away here! Again,
happy to drop it then.

>> +
>> +	dev_dbg(ad->dev, "ch%d descriptor: addr=0x%pad len=0x%zx flags=0x%x\n",
>> +		channo, addr, tx->period_len, FLAG_DESC_NOTIFY);
>> +
>> +	admac_poke(ad, REG_DESC_WRITE(channo), addr);
>> +	admac_poke(ad, REG_DESC_WRITE(channo), addr >> 32);
>> +	admac_poke(ad, REG_DESC_WRITE(channo), tx->period_len);
>> +	admac_poke(ad, REG_DESC_WRITE(channo), FLAG_DESC_NOTIFY);
>> +
>> +	tx->submitted_pos += tx->period_len;
>> +	tx->submitted_pos %= 2 * tx->buf_len;
>> +}

(snip)

>> +static void admac_handle_status_err(struct admac_data *ad, int channo)
>> +{
>> +	bool handled = false;
>> +
>> +	if (admac_peek(ad, REG_DESC_RING(channo) & RING_ERR)) {
>> +		admac_poke(ad, REG_DESC_RING(channo), RING_ERR);
>> +		dev_err(ad->dev, "ch%d descriptor ring error\n", channo);
> 
> It looks this is executed on every interrupt, so you might flood the
> dmesg. This should be ratelimited.

OK

>> +		handled = true;
>> +	}
>> +
>> +	if (admac_peek(ad, REG_REPORT_RING(channo)) & RING_ERR) {
>> +		admac_poke(ad, REG_REPORT_RING(channo), RING_ERR);
>> +		dev_err(ad->dev, "ch%d report ring error\n", channo);
>> +		handled = true;
>> +	}
>> +
>> +	if (unlikely(!handled)) {
>> +		dev_err(ad->dev, "ch%d unknown error, masking errors as cause of IRQs\n", channo);
>> +		admac_modify(ad, REG_CHAN_INTMASK(channo, ad->irq_index),
>> +				STATUS_ERR, 0);
>> +	}
>> +}

(snip)

>> +static int admac_probe(struct platform_device *pdev)
>> +{
>> +	struct device_node *np = pdev->dev.of_node;
>> +	struct admac_data *ad;
>> +	struct dma_device *dma;
>> +	int nchannels;
>> +	int err, irq, i;
>> +
>> +	err = of_property_read_u32(np, "dma-channels", &nchannels);
>> +	if (err || nchannels > NCHANNELS_MAX) {
>> +		dev_err(&pdev->dev, "missing or invalid dma-channels property\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	ad = devm_kzalloc(&pdev->dev, struct_size(ad, channels, nchannels), GFP_KERNEL);
>> +	if (!ad)
>> +		return -ENOMEM;
>> +
>> +	platform_set_drvdata(pdev, ad);
>> +	ad->dev = &pdev->dev;
>> +	ad->nchannels = nchannels;
>> +
>> +	err = of_property_read_u32(np, "apple,internal-irq-destination",
>> +					&ad->irq_index);
>> +	if (err || ad->irq_index >= IRQ_NINDICES) {
>> +		dev_err(&pdev->dev, "missing or invalid apple,internal-irq-destination property\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	irq = platform_get_irq(pdev, 0);
>> +	if (irq < 0) {
>> +		dev_err(&pdev->dev, "unable to obtain interrupt resource\n");
>> +		return irq;
>> +	}
>> +
>> +	err = devm_request_irq(&pdev->dev, irq, admac_interrupt,
>> +					0, dev_name(&pdev->dev), ad);
> 
> Align the arguments with previous line. This applies everywhere in the
> driver.

I hope best-effort tab aligning is okay.

>> +	if (err) {
>> +		dev_err(&pdev->dev, "unable to register interrupt: %d\n", err);
>> +		return err;
>> +	}
>> +
>> +	ad->base = devm_platform_ioremap_resource(pdev, 0);
>> +	if (IS_ERR(ad->base)) {
>> +		dev_err(&pdev->dev, "unable to obtain MMIO resource\n");
>> +		return PTR_ERR(ad->base);
>> +	}
>> +
>> +	dma = &ad->dma;
>> +
>> +	dma_cap_set(DMA_PRIVATE, dma->cap_mask);
>> +	dma_cap_set(DMA_CYCLIC, dma->cap_mask);
>> +
>> +	dma->dev = &pdev->dev;
>> +	dma->device_alloc_chan_resources = admac_alloc_chan_resources;
>> +	dma->device_free_chan_resources = admac_free_chan_resources;
>> +	dma->device_tx_status = admac_tx_status;
>> +	dma->device_issue_pending = admac_issue_pending;
>> +	dma->device_terminate_all = admac_terminate_all;
>> +	dma->device_prep_dma_cyclic = admac_prep_dma_cyclic;
>> +	dma->device_config = admac_device_config;
>> +	dma->device_pause = admac_pause;
>> +	dma->device_resume = admac_resume;
>> +
>> +	dma->directions = BIT(DMA_MEM_TO_DEV) | BIT(DMA_DEV_TO_MEM);
>> +	dma->residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;
>> +	dma->dst_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE) |
>> +			BIT(DMA_SLAVE_BUSWIDTH_2_BYTES) |
>> +			BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
>> +
>> +	INIT_LIST_HEAD(&dma->channels);
>> +	for (i = 0; i < nchannels; i++) {
>> +		struct admac_chan *adchan = &ad->channels[i];
>> +
>> +		adchan->host = ad;
>> +		adchan->no = i;
>> +		adchan->chan.device = &ad->dma;
>> +		spin_lock_init(&adchan->lock);
>> +		INIT_LIST_HEAD(&adchan->submitted);
>> +		INIT_LIST_HEAD(&adchan->issued);
>> +		list_add_tail(&adchan->chan.device_node, &dma->channels);
>> +		tasklet_setup(&adchan->tasklet, admac_chan_tasklet);
>> +	}
>> +
>> +	err = dma_async_device_register(&ad->dma);
>> +	if (err) {
>> +		dev_err(&pdev->dev, "failed to register DMA device: %d\n", err);
> 
> Use dev_err_probe() here and in other places.

Okay!

>> +		return err;
>> +	}
>> +
>> +	err = of_dma_controller_register(pdev->dev.of_node, admac_dma_of_xlate, ad);
>> +	if (err) {
>> +		dev_err(&pdev->dev, "failed to register with OF: %d\n", err);
>> +		dma_async_device_unregister(&ad->dma);
>> +		return err;
>> +	}
>> +
>> +	dev_dbg(&pdev->dev, "all good, ready to go!\n");
> 
> No debugging messages for simple probe success, please.

If you insist. :)

> 
> Best regards,
> Krzysztof

Best, Martin

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