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Subject: Re: [PATCH v1 3/7] spi: qspi-tegra: Add support for Tegra210 QSPI
 controller
To:     Sowjanya Komatineni <skomatineni@nvidia.com>,
        <thierry.reding@gmail.com>, <broonie@kernel.org>,
        <robh+dt@kernel.org>
CC:     <linux-spi@vger.kernel.org>, <linux-tegra@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <devicetree@vger.kernel.org>
References: <1606857168-5839-1-git-send-email-skomatineni@nvidia.com>
 <1606857168-5839-4-git-send-email-skomatineni@nvidia.com>
From:   Jon Hunter <jonathanh@nvidia.com>
Message-ID: <1696afb0-3e44-8a68-caea-22fefd837ad8@nvidia.com>
Date:   Fri, 4 Dec 2020 14:41:57 +0000
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On 01/12/2020 21:12, Sowjanya Komatineni wrote:
> Tegra SoC has a Quad SPI controller starting from Tegra210.
> 
> This patch adds support for Tegra210 QSPI controller.
> 
> Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
> ---
>  drivers/spi/Kconfig      |    9 +
>  drivers/spi/Makefile     |    1 +
>  drivers/spi/qspi-tegra.c | 1418 ++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 1428 insertions(+)
>  create mode 100644 drivers/spi/qspi-tegra.c
> 
> diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
> index 3fd16b7..1a021e8 100644
> --- a/drivers/spi/Kconfig
> +++ b/drivers/spi/Kconfig
> @@ -844,6 +844,15 @@ config SPI_MXS
>  	help
>  	  SPI driver for Freescale MXS devices.
>  
> +config QSPI_TEGRA
> +	tristate "Nvidia Tegra QSPI Controller"
> +	depends on (ARCH_TEGRA && TEGRA20_APB_DMA) || COMPILE_TEST

I assume that the dependency on the APBDMA is for Tegra210. Does it work
on Tegra210 without the DMA? I am wondering if this is a dependency?

> +static void tegra_qspi_deinit_dma_param(struct tegra_qspi_data *tqspi,
> +					bool dma_to_memory)
> +{
> +	u32 *dma_buf;
> +	dma_addr_t dma_phys;
> +	struct dma_chan *dma_chan;
> +
> +	if (dma_to_memory) {
> +		dma_buf = tqspi->rx_dma_buf;
> +		dma_chan = tqspi->rx_dma_chan;
> +		dma_phys = tqspi->rx_dma_phys;
> +		tqspi->rx_dma_chan = NULL;
> +		tqspi->rx_dma_buf = NULL;
> +	} else {
> +		dma_buf = tqspi->tx_dma_buf;
> +		dma_chan = tqspi->tx_dma_chan;
> +		dma_phys = tqspi->tx_dma_phys;
> +		tqspi->tx_dma_buf = NULL;
> +		tqspi->tx_dma_chan = NULL;
> +	}
> +	if (!dma_chan)
> +		return;

The above seemed odd to me at first, but I guess if a device does not
support DMA yet, then this will be NULL. However, would it be clearer to
just ...

        if (!tqspi->use_dma)
		return;

You could also do this right at the beginning of the function.

> +static struct tegra_qspi_client_data
> +	*tegra_qspi_parse_cdata_dt(struct spi_device *spi)
> +{
> +	struct tegra_qspi_client_data *cdata;
> +	struct device_node *slave_np;
> +
> +	slave_np = spi->dev.of_node;
> +	if (!slave_np) {

This test should not be necessary as we only support device-tree.

> +		dev_dbg(&spi->dev, "device node not found\n");
> +		return NULL;
> +	}
> +
> +	cdata = kzalloc(sizeof(*cdata), GFP_KERNEL);
> +	if (!cdata)
> +		return NULL;
> +
> +	of_property_read_u32(slave_np, "nvidia,tx-clk-tap-delay",
> +			     &cdata->tx_clk_tap_delay);
> +	of_property_read_u32(slave_np, "nvidia,rx-clk-tap-delay",
> +			     &cdata->rx_clk_tap_delay);
> +	return cdata;
> +}
> +
> +static void tegra_qspi_cleanup(struct spi_device *spi)
> +{
> +	struct tegra_qspi_client_data *cdata = spi->controller_data;
> +
> +	spi->controller_data = NULL;
> +	if (spi->dev.of_node)
> +		kfree(cdata);
> +}
> +
> +static int tegra_qspi_setup(struct spi_device *spi)
> +{
> +	struct tegra_qspi_data *tqspi = spi_master_get_devdata(spi->master);
> +	struct tegra_qspi_client_data *cdata = spi->controller_data;
> +	u32 tx_tap = 0, rx_tap = 0;
> +	u32 val;
> +	unsigned long flags;
> +	int ret;
> +
> +	dev_dbg(&spi->dev, "setup %d bpw, %scpol, %scpha, %dHz\n",
> +		spi->bits_per_word,
> +		spi->mode & SPI_CPOL ? "" : "~",
> +		spi->mode & SPI_CPHA ? "" : "~",
> +		spi->max_speed_hz);
> +
> +	if (!cdata) {
> +		cdata = tegra_qspi_parse_cdata_dt(spi);
> +		spi->controller_data = cdata;
> +	}
> +
> +	ret = pm_runtime_get_sync(tqspi->dev);
> +	if (ret < 0) {
> +		dev_err(tqspi->dev, "runtime resume failed: %d\n", ret);
> +		if (cdata)
> +			tegra_qspi_cleanup(spi);
> +		return ret;
> +	}

Does it simplify the code to do the pm_runtime_get_sync() before the
parsing of the cdata?

> +static int tegra_qspi_probe(struct platform_device *pdev)
> +{
> +	struct spi_master	*master;
> +	struct tegra_qspi_data	*tqspi;
> +	struct resource		*r;
> +	int ret, qspi_irq;
> +	int bus_num;
> +
> +	master = spi_alloc_master(&pdev->dev, sizeof(*tqspi));
> +	if (!master) {
> +		dev_err(&pdev->dev, "master allocation failed\n");
> +		return -ENOMEM;
> +	}
> +
> +	platform_set_drvdata(pdev, master);
> +	tqspi = spi_master_get_devdata(master);
> +
> +	if (of_property_read_u32(pdev->dev.of_node, "spi-max-frequency",
> +				 &master->max_speed_hz))
> +		master->max_speed_hz = QSPI_MAX_SPEED;
> +
> +	/* the spi->mode bits understood by this driver: */
> +	master->mode_bits = SPI_MODE_0 | SPI_MODE_3 | SPI_CS_HIGH |
> +			    SPI_TX_DUAL | SPI_RX_DUAL | SPI_TX_QUAD |
> +			    SPI_RX_QUAD;
> +	master->bits_per_word_mask = SPI_BPW_MASK(32) | SPI_BPW_MASK(16) |
> +				     SPI_BPW_MASK(8);
> +	master->setup = tegra_qspi_setup;
> +	master->cleanup = tegra_qspi_cleanup;
> +	master->transfer_one_message = tegra_qspi_transfer_one_message;
> +	master->num_chipselect = 1;
> +	master->auto_runtime_pm = true;
> +	bus_num = of_alias_get_id(pdev->dev.of_node, "spi");
> +	if (bus_num >= 0)
> +		master->bus_num = bus_num;
> +
> +	tqspi->master = master;
> +	tqspi->dev = &pdev->dev;
> +	spin_lock_init(&tqspi->lock);
> +
> +	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	tqspi->base = devm_ioremap_resource(&pdev->dev, r);
> +	if (IS_ERR(tqspi->base)) {
> +		ret = PTR_ERR(tqspi->base);
> +		goto exit_free_master;
> +	}
> +
> +	tqspi->phys = r->start;
> +	qspi_irq = platform_get_irq(pdev, 0);
> +	tqspi->irq = qspi_irq;
> +
> +	tqspi->clk = devm_clk_get(&pdev->dev, "qspi");
> +	if (IS_ERR(tqspi->clk)) {
> +		ret = PTR_ERR(tqspi->clk);
> +		dev_err(&pdev->dev, "failed to get clock: %d\n", ret);
> +		goto exit_free_master;
> +	}
> +
> +	tqspi->rst = devm_reset_control_get_exclusive(&pdev->dev, "qspi");
> +	if (IS_ERR(tqspi->rst)) {
> +		ret = PTR_ERR(tqspi->rst);
> +		dev_err(&pdev->dev, "failed to get reset control: %d\n", ret);
> +		goto exit_free_master;
> +	}
> +
> +	tqspi->max_buf_size = QSPI_FIFO_DEPTH << 2;
> +	tqspi->dma_buf_size = DEFAULT_QSPI_DMA_BUF_LEN;
> +
> +	ret = tegra_qspi_init_dma_param(tqspi, true);
> +	if (ret < 0)
> +		goto exit_free_master;
> +	ret = tegra_qspi_init_dma_param(tqspi, false);
> +	if (ret < 0)
> +		goto exit_rx_dma_free;

I would be tempted to combine the init for the TX and RX into a single
function. Then we can have a single function to deinit.

> +
> +	if (tqspi->use_dma)
> +		tqspi->max_buf_size = tqspi->dma_buf_size;
> +
> +	init_completion(&tqspi->tx_dma_complete);
> +	init_completion(&tqspi->rx_dma_complete);
> +

Unnecessary blank line.

> +	init_completion(&tqspi->xfer_completion);
> +
> +	pm_runtime_enable(&pdev->dev);
> +	if (!pm_runtime_enabled(&pdev->dev)) {

RPM is always enabled for Tegra and so if this fails we should just fail.

> +		ret = tegra_qspi_runtime_resume(&pdev->dev);
> +		if (ret)
> +			goto exit_pm_disable;
> +	}
> +
> +	ret = pm_runtime_get_sync(&pdev->dev);
> +	if (ret < 0) {
> +		dev_err(&pdev->dev, "runtime resume failed: %d\n", ret);
> +		pm_runtime_put_noidle(&pdev->dev)
You can use pm_runtime_resume_and_get() now and then you don't need to
call pm_runtime_put_noidle() on failure.

> +		goto exit_pm_disable;
> +	}
> +
> +	reset_control_assert(tqspi->rst);
> +	udelay(2);
> +	reset_control_deassert(tqspi->rst);
> +	tqspi->def_command1_reg = QSPI_M_S | QSPI_CS_SW_HW |  QSPI_CS_SW_VAL;
> +	tegra_qspi_writel(tqspi, tqspi->def_command1_reg, QSPI_COMMAND1);
> +	tqspi->spi_cs_timing1 = tegra_qspi_readl(tqspi, QSPI_CS_TIMING1);
> +	tqspi->spi_cs_timing2 = tegra_qspi_readl(tqspi, QSPI_CS_TIMING2);
> +	tqspi->def_command2_reg = tegra_qspi_readl(tqspi, QSPI_COMMAND2);
> +
> +	pm_runtime_put(&pdev->dev);
> +
> +	ret = request_threaded_irq(tqspi->irq, tegra_qspi_isr,
> +				   tegra_qspi_isr_thread, IRQF_ONESHOT,
> +				   dev_name(&pdev->dev), tqspi);
> +	if (ret < 0) {
> +		dev_err(&pdev->dev,
> +			"failed to request IRQ#%u: %d\n", tqspi->irq, ret);
> +		goto exit_pm_disable;
> +	}
> +
> +	master->dev.of_node = pdev->dev.of_node;
> +	ret = devm_spi_register_master(&pdev->dev, master);
> +	if (ret < 0) {
> +		dev_err(&pdev->dev, "failed to register master: %d\n", ret);
> +		goto exit_free_irq;
> +	}
> +	return ret;

return 0

> +static int tegra_qspi_runtime_resume(struct device *dev)
> +{
> +	struct spi_master *master = dev_get_drvdata(dev);
> +	struct tegra_qspi_data *tqspi = spi_master_get_devdata(master);
> +	int ret;
> +
> +	ret = clk_prepare_enable(tqspi->clk);
> +	if (ret < 0) {
> +		dev_err(tqspi->dev, "clk_prepare failed: %d\n", ret);
> +		return ret;
> +	}
> +	return 0;

Always just 'return ret' here.

Cheers
Jon

-- 
nvpublic