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Message-ID: <X8onZQRMLxV5spo+@ulmo>
Date: Fri, 4 Dec 2020 13:11:17 +0100
From: Thierry Reding <thierry.reding@...il.com>
To: Sowjanya Komatineni <skomatineni@...dia.com>
Cc: jonathanh@...dia.com, broonie@...nel.org, robh+dt@...nel.org,
linux-spi@...r.kernel.org, linux-tegra@...r.kernel.org,
linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v1 3/7] spi: qspi-tegra: Add support for Tegra210 QSPI
controller
On Tue, Dec 01, 2020 at 01:12:44PM -0800, 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@...dia.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
You already discussed this with Mark, but perhaps a better name would be
SPI_TEGRA210_QUAD or something. SPI_TEGRA210 is too generic because
there is a regular SPI controller on Tegra210 as well.
SPI_TEGRA210_QUAD is in line with the likes of SPI_TEGRA20_SFLASH and
SPI_TEGRA20_SLINK.
> + tristate "Nvidia Tegra QSPI Controller"
NVIDIA
> + depends on (ARCH_TEGRA && TEGRA20_APB_DMA) || COMPILE_TEST
I don't think we need the ARCH_TEGRA part there because TEGRA20_APB_DMA
already depends on that. Also, there's not strictly a dependency on
TEGRA20_APB_DMA specifically, but rather a dependency on DMA_ENGINE,
right? The DMA channels could be coming from some other driver on some
other SoC generation, such as the Tegra186 and later GPCDMA.
> + depends on RESET_CONTROLLER
> + help
> + QSPI driver for Nvidia Tegra QSPI Controller interface. This
NVIDIA
> + controller is different from the spi controller and is available
SPI
> + on Tegra SoCs starting from Tegra210.
> +
> config SPI_TEGRA114
> tristate "NVIDIA Tegra114 SPI Controller"
> depends on (ARCH_TEGRA && TEGRA20_APB_DMA) || COMPILE_TEST
[...]
> diff --git a/drivers/spi/qspi-tegra.c b/drivers/spi/qspi-tegra.c
[...]
> +struct tegra_qspi_client_data {
> + int tx_clk_tap_delay;
> + int rx_clk_tap_delay;
> +};
If this is client data, why are we dealing with this in the controller
driver? Is this perhaps something that could be added to struct
spi_device?
> +
> +struct tegra_qspi_data {
That _data just seems to be 5 extra characters that don't add any value.
> + struct device *dev;
> + struct spi_master *master;
> + /* Lock to protect data accessed by irq */
> + spinlock_t lock;
> +
> + struct clk *clk;
> + struct reset_control *rst;
> + void __iomem *base;
> + phys_addr_t phys;
> + unsigned int irq;
> +
> + u32 cur_speed;
> + unsigned int cur_pos;
> + unsigned int words_per_32bit;
> + unsigned int bytes_per_word;
> + unsigned int curr_dma_words;
> + unsigned int cur_direction;
> +
> + unsigned int cur_rx_pos;
> + unsigned int cur_tx_pos;
> +
> + unsigned int dma_buf_size;
> + unsigned int max_buf_size;
> + bool is_curr_dma_xfer;
> +
> + struct completion rx_dma_complete;
> + struct completion tx_dma_complete;
> +
> + u32 tx_status;
> + u32 rx_status;
> + u32 status_reg;
> + bool is_packed;
> + bool use_dma;
> +
> + u32 command1_reg;
> + u32 dma_control_reg;
> + u32 def_command1_reg;
> + u32 def_command2_reg;
> + u32 spi_cs_timing1;
> + u32 spi_cs_timing2;
> + u8 dummy_cycles;
> +
> + struct completion xfer_completion;
> + struct spi_transfer *curr_xfer;
> +
> + struct dma_chan *rx_dma_chan;
> + u32 *rx_dma_buf;
> + dma_addr_t rx_dma_phys;
> + struct dma_async_tx_descriptor *rx_dma_desc;
> +
> + struct dma_chan *tx_dma_chan;
> + u32 *tx_dma_buf;
> + dma_addr_t tx_dma_phys;
> + struct dma_async_tx_descriptor *tx_dma_desc;
> +};
> +
> +static int tegra_qspi_runtime_suspend(struct device *dev);
> +static int tegra_qspi_runtime_resume(struct device *dev);
Can't we just reorder the code so that these don't have to be forward-
declared?
> +
> +static inline u32 tegra_qspi_readl(struct tegra_qspi_data *tqspi,
> + unsigned long reg)
Nit: I prefer "offset" over "reg" because I think it's slightly more
accurate.
> +{
> + return readl(tqspi->base + reg);
> +}
> +
> +static inline void tegra_qspi_writel(struct tegra_qspi_data *tqspi,
> + u32 val, unsigned long reg)
I also prefer "value" over "val" because "val" could also be short for
"valid". Anyway, I am pedantic that way, so feel free to ignore that.
[...]
> +static unsigned int
> +tegra_qspi_calculate_curr_xfer_param(struct tegra_qspi_data *tqspi,
> + struct spi_transfer *t)
> +{
> + unsigned int remain_len = t->len - tqspi->cur_pos;
> + unsigned int max_word;
> + unsigned int bits_per_word = t->bits_per_word;
> + unsigned int max_len;
> + unsigned int total_fifo_words;
You could list some of these on the same line to make this a bit more
compact. Something I've often seen done that makes this really clean is
to have uninitialized variables on one line and then assignments on
separate lines, then sort lines by length:
unsigned int max_word, max_len, total_fifo_words;
unsigned int remain_len = t->len - tqspi->cur_pos;
unsigned int bits_per_word = t->bits_per_word;
This also applies to some other functions further down.
[...]
> +static void
> +tegra_qspi_copy_client_txbuf_to_qspi_txbuf(struct tegra_qspi_data *tqspi,
> + struct spi_transfer *t)
> +{
> + /* Make the dma buffer to read by cpu */
This comment seems a bit redundant. dma_sync_single_for_cpu() is a well-
documented function that doesn't need explanation.
> + dma_sync_single_for_cpu(tqspi->dev, tqspi->tx_dma_phys,
> + tqspi->dma_buf_size, DMA_TO_DEVICE);
> +
> + if (tqspi->is_packed) {
> + unsigned int len = tqspi->curr_dma_words *
> + tqspi->bytes_per_word;
> +
> + memcpy(tqspi->tx_dma_buf, t->tx_buf + tqspi->cur_pos, len);
> + tqspi->cur_tx_pos += tqspi->curr_dma_words *
> + tqspi->bytes_per_word;
> + } else {
> + u8 *tx_buf = (u8 *)t->tx_buf + tqspi->cur_tx_pos;
> + unsigned int i;
> + unsigned int count;
> + unsigned int consume;
> + unsigned int write_bytes;
> +
> + consume = tqspi->curr_dma_words * tqspi->bytes_per_word;
> + if (consume > t->len - tqspi->cur_pos)
> + consume = t->len - tqspi->cur_pos;
> + write_bytes = consume;
> + for (count = 0; count < tqspi->curr_dma_words; count++) {
> + u32 x = 0;
> +
> + for (i = 0; consume && (i < tqspi->bytes_per_word);
> + i++, consume--)
> + x |= (u32)(*tx_buf++) << (i * 8);
> + tqspi->tx_dma_buf[count] = x;
> + }
> +
> + tqspi->cur_tx_pos += write_bytes;
> + }
> +
> + /* Make the dma buffer to read by dma */
Same here.
> + dma_sync_single_for_device(tqspi->dev, tqspi->tx_dma_phys,
> + tqspi->dma_buf_size, DMA_TO_DEVICE);
> +}
> +
> +static void
> +tegra_qspi_copy_qspi_rxbuf_to_client_rxbuf(struct tegra_qspi_data *tqspi,
> + struct spi_transfer *t)
> +{
> + /* Make the dma buffer to read by cpu */
And here.
> + dma_sync_single_for_cpu(tqspi->dev, tqspi->rx_dma_phys,
> + tqspi->dma_buf_size, DMA_FROM_DEVICE);
> +
> + if (tqspi->is_packed) {
> + unsigned int len = tqspi->curr_dma_words *
> + tqspi->bytes_per_word;
> +
> + memcpy(t->rx_buf + tqspi->cur_rx_pos, tqspi->rx_dma_buf, len);
> + tqspi->cur_rx_pos += tqspi->curr_dma_words *
> + tqspi->bytes_per_word;
> + } else {
> + unsigned char *rx_buf = t->rx_buf + tqspi->cur_rx_pos;
> + u32 rx_mask = ((u32)1 << t->bits_per_word) - 1;
> + unsigned int i;
> + unsigned int count;
> + unsigned int consume;
> + unsigned int read_bytes;
> +
> + consume = tqspi->curr_dma_words * tqspi->bytes_per_word;
> + if (consume > t->len - tqspi->cur_pos)
> + consume = t->len - tqspi->cur_pos;
> + read_bytes = consume;
> + for (count = 0; count < tqspi->curr_dma_words; count++) {
> + u32 x = tqspi->rx_dma_buf[count] & rx_mask;
> +
> + for (i = 0; consume && (i < tqspi->bytes_per_word);
> + i++, consume--)
> + *rx_buf++ = (x >> (i * 8)) & 0xFF;
> + }
> +
> + tqspi->cur_rx_pos += read_bytes;
> + }
> +
> + /* Make the dma buffer to read by dma */
And here.
> + dma_sync_single_for_device(tqspi->dev, tqspi->rx_dma_phys,
> + tqspi->dma_buf_size, DMA_FROM_DEVICE);
> +}
> +
> +static void tegra_qspi_dma_complete(void *args)
> +{
> + struct completion *dma_complete = args;
> +
> + complete(dma_complete);
> +}
> +
> +static int tegra_qspi_start_tx_dma(struct tegra_qspi_data *tqspi, int len)
> +{
> + reinit_completion(&tqspi->tx_dma_complete);
> + tqspi->tx_dma_desc = dmaengine_prep_slave_single(tqspi->tx_dma_chan,
> + tqspi->tx_dma_phys, len, DMA_MEM_TO_DEV,
> + DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
Looks like most of this driver is wrapped at 80 columns. That rule was
relaxed a bit a while ago and checkpatch now only warns if you exceed
100 columns. There are various places in this driver that could benefit
from longer lines, such as the above.
> + if (!tqspi->tx_dma_desc) {
> + dev_err(tqspi->dev, "Not able to get desc for Tx\n");
Perhaps: "Unable to get TX descriptor\n"?
> + return -EIO;
> + }
> +
> + tqspi->tx_dma_desc->callback = tegra_qspi_dma_complete;
> + tqspi->tx_dma_desc->callback_param = &tqspi->tx_dma_complete;
> +
> + dmaengine_submit(tqspi->tx_dma_desc);
> + dma_async_issue_pending(tqspi->tx_dma_chan);
> + return 0;
> +}
> +
> +static int tegra_qspi_start_rx_dma(struct tegra_qspi_data *tqspi, int len)
> +{
> + reinit_completion(&tqspi->rx_dma_complete);
> + tqspi->rx_dma_desc = dmaengine_prep_slave_single(tqspi->rx_dma_chan,
> + tqspi->rx_dma_phys, len, DMA_DEV_TO_MEM,
> + DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
> + if (!tqspi->rx_dma_desc) {
> + dev_err(tqspi->dev, "Not able to get desc for Rx\n");
Same here.
> + return -EIO;
> + }
> +
> + tqspi->rx_dma_desc->callback = tegra_qspi_dma_complete;
> + tqspi->rx_dma_desc->callback_param = &tqspi->rx_dma_complete;
> +
> + dmaengine_submit(tqspi->rx_dma_desc);
> + dma_async_issue_pending(tqspi->rx_dma_chan);
> + return 0;
> +}
> +
> +static int tegra_qspi_flush_fifos(struct tegra_qspi_data *tqspi)
> +{
> + unsigned long timeout = jiffies + HZ;
> + u32 status;
> +
> + status = tegra_qspi_readl(tqspi, QSPI_FIFO_STATUS);
> + if ((status & QSPI_FIFO_EMPTY) == QSPI_FIFO_EMPTY)
> + return 0;
> +
> + status |= QSPI_RX_FIFO_FLUSH | QSPI_TX_FIFO_FLUSH;
> + tegra_qspi_writel(tqspi, status, QSPI_FIFO_STATUS);
> + while ((status & QSPI_FIFO_EMPTY) != QSPI_FIFO_EMPTY) {
> + status = tegra_qspi_readl(tqspi, QSPI_FIFO_STATUS);
> + if (time_after(jiffies, timeout)) {
> + dev_err(tqspi->dev,
> + "timeout waiting for fifo flush\n");
FIFO is an abbreviation, so it should be all uppercase in text.
> + return -EIO;
> + }
> +
> + udelay(1);
It looks like this function can be called from both interrupt and
process contexts, where the latter is the more common case and it is
only ever used in interrupt context to clean up on error.
I wonder if it's worth adding an "atomic" parameter to the function and
make this a sleeping loop whenever possible. Also, can this not use one
of the helpers from linux/iopoll.h?
> + }
> +
> + return 0;
> +}
> +
> +static void tegra_qspi_unmask_irq(struct tegra_qspi_data *tqspi)
> +{
> + u32 intr_mask;
> +
> + intr_mask = tegra_qspi_readl(tqspi, QSPI_INTR_MASK);
> + intr_mask &= ~(QSPI_INTR_RDY_MASK | QSPI_INTR_RX_TX_FIFO_ERR);
> + tegra_qspi_writel(tqspi, intr_mask, QSPI_INTR_MASK);
> +}
> +
> +static int tegra_qspi_start_dma_based_transfer(struct tegra_qspi_data *tqspi,
> + struct spi_transfer *t)
> +{
> + u32 val;
> + unsigned int len;
> + int ret = 0;
> + u8 dma_burst;
> + struct dma_slave_config dma_sconfig = {0};
I think checkpatch wants spaces after { and before }.
> +
> + val = QSPI_DMA_BLK_SET(tqspi->curr_dma_words - 1);
> + tegra_qspi_writel(tqspi, val, QSPI_DMA_BLK);
> +
> + tegra_qspi_unmask_irq(tqspi);
> +
> + if (tqspi->is_packed)
> + len = DIV_ROUND_UP(tqspi->curr_dma_words *
> + tqspi->bytes_per_word, 4) * 4;
> + else
> + len = tqspi->curr_dma_words * 4;
> +
> + /* Set attention level based on length of transfer */
> + val = 0;
> + if (len & 0xF) {
Nit: hexadecimal literals are usually lowercase.
> + val |= QSPI_TX_TRIG_1 | QSPI_RX_TRIG_1;
> + dma_burst = 1;
> + } else if (((len) >> 4) & 0x1) {
> + val |= QSPI_TX_TRIG_4 | QSPI_RX_TRIG_4;
> + dma_burst = 4;
> + } else {
> + val |= QSPI_TX_TRIG_8 | QSPI_RX_TRIG_8;
> + dma_burst = 8;
> + }
> +
> + tegra_qspi_writel(tqspi, val, QSPI_DMA_CTL);
> + tqspi->dma_control_reg = val;
> +
> + dma_sconfig.device_fc = true;
> + if (tqspi->cur_direction & DATA_DIR_TX) {
> + dma_sconfig.dst_addr = tqspi->phys + QSPI_TX_FIFO;
> + dma_sconfig.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
> + dma_sconfig.dst_maxburst = dma_burst;
> + ret = dmaengine_slave_config(tqspi->tx_dma_chan, &dma_sconfig);
> + if (ret < 0) {
> + dev_err(tqspi->dev,
> + "DMA slave config failed: %d\n", ret);
> + return ret;
> + }
> +
> + tegra_qspi_copy_client_txbuf_to_qspi_txbuf(tqspi, t);
> + ret = tegra_qspi_start_tx_dma(tqspi, len);
> + if (ret < 0) {
> + dev_err(tqspi->dev,
> + "Starting tx dma failed: %d\n", ret);
"TX" and "DMA"
> + return ret;
> + }
> + }
> +
> + if (tqspi->cur_direction & DATA_DIR_RX) {
> + dma_sconfig.src_addr = tqspi->phys + QSPI_RX_FIFO;
> + dma_sconfig.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
> + dma_sconfig.src_maxburst = dma_burst;
> + ret = dmaengine_slave_config(tqspi->rx_dma_chan, &dma_sconfig);
> + if (ret < 0) {
> + dev_err(tqspi->dev,
> + "DMA slave config failed: %d\n", ret);
> + return ret;
> + }
> +
> + /* Make the dma buffer to read by dma */
Again, not a useful comment.
> + dma_sync_single_for_device(tqspi->dev, tqspi->rx_dma_phys,
> + tqspi->dma_buf_size,
> + DMA_FROM_DEVICE);
> +
> + ret = tegra_qspi_start_rx_dma(tqspi, len);
> + if (ret < 0) {
> + dev_err(tqspi->dev,
> + "Starting rx dma failed: %d\n", ret);
"RX" and "DMA"
[...]
> +static int tegra_qspi_init_dma_param(struct tegra_qspi_data *tqspi,
> + bool dma_to_memory)
> +{
> + struct dma_chan *dma_chan;
> + u32 *dma_buf;
> + dma_addr_t dma_phys;
> +
> + if (!device_property_present(tqspi->dev, "dmas"))
> + return 0;
If DMA support is optional, then we definitely don't want to depend on
TEGRA20_APB_DMA (or any other specific driver).
> +
> + dma_chan = dma_request_chan(tqspi->dev, dma_to_memory ? "rx" : "tx");
Does this return some specific value when there's no channel for this?
I.e. what happens if the "dmas" property exists in device tree but we
don't have a driver for the provider enabled? Since we have code to use
as fallback, we may want to special case that here and allow the driver
to continue.
> + if (IS_ERR(dma_chan))
> + return dev_err_probe(tqspi->dev, PTR_ERR(dma_chan),
> + "Dma channel is not available\n");
"DMA"
[...]
> +static int tegra_qspi_start_transfer_one(struct spi_device *spi,
> + struct spi_transfer *t, u32 command1)
> +{
[...]
> + command1 &= ~QSPI_INTERFACE_WIDTH_MASK;
> + if (bus_width == SPI_NBITS_QUAD)
> + command1 |= QSPI_INTERFACE_WIDTH_QUAD;
> + else if (bus_width == SPI_NBITS_DUAL)
> + command1 |= QSPI_INTERFACE_WIDTH_DUAL;
> + else
> + command1 |= QSPI_INTERFACE_WIDTH_SINGLE;
> + tqspi->command1_reg = command1;
This (and in some other places in the driver) could use a couple of
blank lines to make this less cluttered.
[...]
> +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)
Can this ever fail? Do we support SPI device instantiation from
somewhere else than DT?
> + 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);
Oh... I see that this is actually parsed from the SPI device node, so
perhaps this is okay to do.
[...]
> +static int tegra_qspi_transfer_one_message(struct spi_master *master,
> + struct spi_message *msg)
> +{
[...]
> + is_first_msg = false;
> + ret = wait_for_completion_timeout(&tqspi->xfer_completion,
> + QSPI_DMA_TIMEOUT);
> + if (WARN_ON(ret == 0)) {
> + dev_err(tqspi->dev,
> + "qspi transfer timeout: %d\n", ret);
"QSPI", or alternatively leave this out completely because it should be
obvious that the transfer that failed is a QSPI transfer just from the
device name.
> + if (tqspi->is_curr_dma_xfer &&
> + (tqspi->cur_direction & DATA_DIR_TX))
> + dmaengine_terminate_all(tqspi->tx_dma_chan);
> + if (tqspi->is_curr_dma_xfer &&
> + (tqspi->cur_direction & DATA_DIR_RX))
> + dmaengine_terminate_all(tqspi->rx_dma_chan);
> + ret = -EIO;
> + tegra_qspi_dump_regs(tqspi);
> + tegra_qspi_flush_fifos(tqspi);
> + reset_control_assert(tqspi->rst);
> + udelay(2);
> + reset_control_deassert(tqspi->rst);
> + goto exit;
> + }
> +
> + if (tqspi->tx_status || tqspi->rx_status) {
> + ret = -EIO;
> + dev_err(tqspi->dev, "error in transfer: %d\n", ret);
Would it make sense to output tx_status and/or rx_status in this message
rather than -EIO unconditionally?
[...]
> +static irqreturn_t handle_cpu_based_xfer(struct tegra_qspi_data *tqspi)
> +{
> + struct spi_transfer *t = tqspi->curr_xfer;
> + unsigned long flags;
> +
> + spin_lock_irqsave(&tqspi->lock, flags);
> + if (tqspi->tx_status || tqspi->rx_status) {
> + dev_err(tqspi->dev, "CpuXfer ERROR bit set 0x%x\n",
> + tqspi->status_reg);
> + dev_err(tqspi->dev, "CpuXfer 0x%08x:0x%08x\n",
> + tqspi->command1_reg, tqspi->dma_control_reg);
> + tegra_qspi_dump_regs(tqspi);
> + tegra_qspi_flush_fifos(tqspi);
> + complete(&tqspi->xfer_completion);
> + spin_unlock_irqrestore(&tqspi->lock, flags);
> + reset_control_assert(tqspi->rst);
> + udelay(2);
> + reset_control_deassert(tqspi->rst);
> + return IRQ_HANDLED;
> + }
Can this error handling be somehow unified with the DMA error handling?
Having markers such as "CpuXfer" in error messages is not really helpful
to users. Maybe have the driver output an INFO message or so during
probe when it falls back to PIO mode, that would be a good enough
indicator to someone debugging some issue that PIO mode is being used.
And then you can just treat transfer failures more uniformly.
Thierry
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