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Date: Mon, 26 Aug 2019 11:59:08 +0000
From: "Sverdlin, Alexander (Nokia - DE/Ulm)" <alexander.sverdlin@...ia.com>
To: "Adamski, Krzysztof (Nokia - PL/Wroclaw)"
<krzysztof.adamski@...ia.com>, Wolfram Sang <wsa@...-dreams.de>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>
Subject: Re: [PATCH v3] i2c: axxia: support slave mode
Hi!
On 19/08/2019 11:07, Adamski, Krzysztof (Nokia - PL/Wroclaw) wrote:
> This device contains both master and slave controllers which can be
> enabled simultaneously. Both controllers share the same SDA/SCL lines
> and interrupt source but has separate control and status registers.
> Controllers also works in loopback mode - slave device can communicate
> with its own master controller internally. The controller can handle up
> to two addresses, both of which may be 10 bit. Most of the logic
> (sending (N)ACK, handling repeated start or switching between
> write/read) is handled automatically which makes working with this
> controller quite easy.
>
> For simplicity, this patch adds basic support, limiting to only one
> slave address. Support for the 2nd device may be added in the future.
>
> Note that synchronize_irq() is used to ensure any running slave interrupt
> is finished to make sure slave i2c_client structure can be safely used
> by i2c_slave_event.
Reviewed-by: Alexander Sverdlin <alexander.sverdlin@...ia.com>
> Signed-off-by: Krzysztof Adamski <krzysztof.adamski@...ia.com>
> ---
> Changes in v3:
> - Fixed braces for one-line if bodies
>
> Changes in v2:
> - Reduced the number of dev_dbg messages.
>
> drivers/i2c/busses/Kconfig | 1 +
> drivers/i2c/busses/i2c-axxia.c | 152 +++++++++++++++++++++++++++++++--
> 2 files changed, 145 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> index 69f19312a574..b8262301c86d 100644
> --- a/drivers/i2c/busses/Kconfig
> +++ b/drivers/i2c/busses/Kconfig
> @@ -429,6 +429,7 @@ config I2C_AXXIA
> tristate "Axxia I2C controller"
> depends on ARCH_AXXIA || COMPILE_TEST
> default ARCH_AXXIA
> + select I2C_SLAVE
> help
> Say yes if you want to support the I2C bus on Axxia platforms.
>
> diff --git a/drivers/i2c/busses/i2c-axxia.c b/drivers/i2c/busses/i2c-axxia.c
> index ff3142b15cab..0214daa913ff 100644
> --- a/drivers/i2c/busses/i2c-axxia.c
> +++ b/drivers/i2c/busses/i2c-axxia.c
> @@ -77,6 +77,40 @@
> MST_STATUS_IP)
> #define MST_TX_BYTES_XFRD 0x50
> #define MST_RX_BYTES_XFRD 0x54
> +#define SLV_ADDR_DEC_CTL 0x58
> +#define SLV_ADDR_DEC_GCE BIT(0) /* ACK to General Call Address from own master (loopback) */
> +#define SLV_ADDR_DEC_OGCE BIT(1) /* ACK to General Call Address from external masters */
> +#define SLV_ADDR_DEC_SA1E BIT(2) /* ACK to addr_1 enabled */
> +#define SLV_ADDR_DEC_SA1M BIT(3) /* 10-bit addressing for addr_1 enabled */
> +#define SLV_ADDR_DEC_SA2E BIT(4) /* ACK to addr_2 enabled */
> +#define SLV_ADDR_DEC_SA2M BIT(5) /* 10-bit addressing for addr_2 enabled */
> +#define SLV_ADDR_1 0x5c
> +#define SLV_ADDR_2 0x60
> +#define SLV_RX_CTL 0x64
> +#define SLV_RX_ACSA1 BIT(0) /* Generate ACK for writes to addr_1 */
> +#define SLV_RX_ACSA2 BIT(1) /* Generate ACK for writes to addr_2 */
> +#define SLV_RX_ACGCA BIT(2) /* ACK data phase transfers to General Call Address */
> +#define SLV_DATA 0x68
> +#define SLV_RX_FIFO 0x6c
> +#define SLV_FIFO_DV1 BIT(0) /* Data Valid for addr_1 */
> +#define SLV_FIFO_DV2 BIT(1) /* Data Valid for addr_2 */
> +#define SLV_FIFO_AS BIT(2) /* (N)ACK Sent */
> +#define SLV_FIFO_TNAK BIT(3) /* Timeout NACK */
> +#define SLV_FIFO_STRC BIT(4) /* First byte after start condition received */
> +#define SLV_FIFO_RSC BIT(5) /* Repeated Start Condition */
> +#define SLV_FIFO_STPC BIT(6) /* Stop Condition */
> +#define SLV_FIFO_DV (SLV_FIFO_DV1 | SLV_FIFO_DV2)
> +#define SLV_INT_ENABLE 0x70
> +#define SLV_INT_STATUS 0x74
> +#define SLV_STATUS_RFH BIT(0) /* FIFO service */
> +#define SLV_STATUS_WTC BIT(1) /* Write transfer complete */
> +#define SLV_STATUS_SRS1 BIT(2) /* Slave read from addr 1 */
> +#define SLV_STATUS_SRRS1 BIT(3) /* Repeated start from addr 1 */
> +#define SLV_STATUS_SRND1 BIT(4) /* Read request not following start condition */
> +#define SLV_STATUS_SRC1 BIT(5) /* Read canceled */
> +#define SLV_STATUS_SRAT1 BIT(6) /* Slave Read timed out */
> +#define SLV_STATUS_SRDRE1 BIT(7) /* Data written after timed out */
> +#define SLV_READ_DUMMY 0x78
> #define SCL_HIGH_PERIOD 0x80
> #define SCL_LOW_PERIOD 0x84
> #define SPIKE_FLTR_LEN 0x88
> @@ -111,6 +145,8 @@ struct axxia_i2c_dev {
> struct clk *i2c_clk;
> u32 bus_clk_rate;
> bool last;
> + struct i2c_client *slave;
> + int irq;
> };
>
> static void i2c_int_disable(struct axxia_i2c_dev *idev, u32 mask)
> @@ -276,13 +312,65 @@ static int axxia_i2c_fill_tx_fifo(struct axxia_i2c_dev *idev)
> return ret;
> }
>
> +static void axxia_i2c_slv_fifo_event(struct axxia_i2c_dev *idev)
> +{
> + u32 fifo_status = readl(idev->base + SLV_RX_FIFO);
> + u8 val;
> +
> + dev_dbg(idev->dev, "slave irq fifo_status=0x%x\n", fifo_status);
> +
> + if (fifo_status & SLV_FIFO_DV1) {
> + if (fifo_status & SLV_FIFO_STRC)
> + i2c_slave_event(idev->slave,
> + I2C_SLAVE_WRITE_REQUESTED, &val);
> +
> + val = readl(idev->base + SLV_DATA);
> + i2c_slave_event(idev->slave, I2C_SLAVE_WRITE_RECEIVED, &val);
> + }
> + if (fifo_status & SLV_FIFO_STPC) {
> + readl(idev->base + SLV_DATA); /* dummy read */
> + i2c_slave_event(idev->slave, I2C_SLAVE_STOP, &val);
> + }
> + if (fifo_status & SLV_FIFO_RSC)
> + readl(idev->base + SLV_DATA); /* dummy read */
> +}
> +
> +static irqreturn_t axxia_i2c_slv_isr(struct axxia_i2c_dev *idev)
> +{
> + u32 status = readl(idev->base + SLV_INT_STATUS);
> + u8 val;
> +
> + dev_dbg(idev->dev, "slave irq status=0x%x\n", status);
> +
> + if (status & SLV_STATUS_RFH)
> + axxia_i2c_slv_fifo_event(idev);
> + if (status & SLV_STATUS_SRS1) {
> + i2c_slave_event(idev->slave, I2C_SLAVE_READ_REQUESTED, &val);
> + writel(val, idev->base + SLV_DATA);
> + }
> + if (status & SLV_STATUS_SRND1) {
> + i2c_slave_event(idev->slave, I2C_SLAVE_READ_PROCESSED, &val);
> + writel(val, idev->base + SLV_DATA);
> + }
> + if (status & SLV_STATUS_SRC1)
> + i2c_slave_event(idev->slave, I2C_SLAVE_STOP, &val);
> +
> + writel(INT_SLV, idev->base + INTERRUPT_STATUS);
> + return IRQ_HANDLED;
> +}
> +
> static irqreturn_t axxia_i2c_isr(int irq, void *_dev)
> {
> struct axxia_i2c_dev *idev = _dev;
> + irqreturn_t ret = IRQ_NONE;
> u32 status;
>
> - if (!(readl(idev->base + INTERRUPT_STATUS) & INT_MST))
> - return IRQ_NONE;
> + status = readl(idev->base + INTERRUPT_STATUS);
> +
> + if (status & INT_SLV)
> + ret = axxia_i2c_slv_isr(idev);
> + if (!(status & INT_MST))
> + return ret;
>
> /* Read interrupt status bits */
> status = readl(idev->base + MST_INT_STATUS);
> @@ -583,9 +671,58 @@ static u32 axxia_i2c_func(struct i2c_adapter *adap)
> return caps;
> }
>
> +static int axxia_i2c_reg_slave(struct i2c_client *slave)
> +{
> + struct axxia_i2c_dev *idev = i2c_get_adapdata(slave->adapter);
> + u32 slv_int_mask = SLV_STATUS_RFH;
> + u32 dec_ctl;
> +
> + if (idev->slave)
> + return -EBUSY;
> +
> + idev->slave = slave;
> +
> + /* Enable slave mode as well */
> + writel(GLOBAL_MST_EN | GLOBAL_SLV_EN, idev->base + GLOBAL_CONTROL);
> + writel(INT_MST | INT_SLV, idev->base + INTERRUPT_ENABLE);
> +
> + /* Set slave address */
> + dec_ctl = SLV_ADDR_DEC_SA1E;
> + if (slave->flags & I2C_CLIENT_TEN)
> + dec_ctl |= SLV_ADDR_DEC_SA1M;
> +
> + writel(SLV_RX_ACSA1, idev->base + SLV_RX_CTL);
> + writel(dec_ctl, idev->base + SLV_ADDR_DEC_CTL);
> + writel(slave->addr, idev->base + SLV_ADDR_1);
> +
> + /* Enable interrupts */
> + slv_int_mask |= SLV_STATUS_SRS1 | SLV_STATUS_SRRS1 | SLV_STATUS_SRND1;
> + slv_int_mask |= SLV_STATUS_SRC1;
> + writel(slv_int_mask, idev->base + SLV_INT_ENABLE);
> +
> + return 0;
> +}
> +
> +static int axxia_i2c_unreg_slave(struct i2c_client *slave)
> +{
> + struct axxia_i2c_dev *idev = i2c_get_adapdata(slave->adapter);
> +
> + /* Disable slave mode */
> + writel(GLOBAL_MST_EN, idev->base + GLOBAL_CONTROL);
> + writel(INT_MST, idev->base + INTERRUPT_ENABLE);
> +
> + synchronize_irq(idev->irq);
> +
> + idev->slave = NULL;
> +
> + return 0;
> +}
> +
> static const struct i2c_algorithm axxia_i2c_algo = {
> .master_xfer = axxia_i2c_xfer,
> .functionality = axxia_i2c_func,
> + .reg_slave = axxia_i2c_reg_slave,
> + .unreg_slave = axxia_i2c_unreg_slave,
> };
>
> static const struct i2c_adapter_quirks axxia_i2c_quirks = {
> @@ -599,7 +736,6 @@ static int axxia_i2c_probe(struct platform_device *pdev)
> struct axxia_i2c_dev *idev = NULL;
> struct resource *res;
> void __iomem *base;
> - int irq;
> int ret = 0;
>
> idev = devm_kzalloc(&pdev->dev, sizeof(*idev), GFP_KERNEL);
> @@ -611,10 +747,10 @@ static int axxia_i2c_probe(struct platform_device *pdev)
> if (IS_ERR(base))
> return PTR_ERR(base);
>
> - irq = platform_get_irq(pdev, 0);
> - if (irq < 0) {
> + idev->irq = platform_get_irq(pdev, 0);
> + if (idev->irq < 0) {
> dev_err(&pdev->dev, "missing interrupt resource\n");
> - return irq;
> + return idev->irq;
> }
>
> idev->i2c_clk = devm_clk_get(&pdev->dev, "i2c");
> @@ -643,10 +779,10 @@ static int axxia_i2c_probe(struct platform_device *pdev)
> goto error_disable_clk;
> }
>
> - ret = devm_request_irq(&pdev->dev, irq, axxia_i2c_isr, 0,
> + ret = devm_request_irq(&pdev->dev, idev->irq, axxia_i2c_isr, 0,
> pdev->name, idev);
> if (ret) {
> - dev_err(&pdev->dev, "failed to claim IRQ%d\n", irq);
> + dev_err(&pdev->dev, "failed to claim IRQ%d\n", idev->irq);
> goto error_disable_clk;
> }
--
Best regards,
Alexander Sverdlin.
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