From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thierry Reding Subject: Re: [PATCH V1] i2c: tegra: Add Bus Clear Master Support Date: Thu, 10 Jan 2019 16:21:48 +0100 Message-ID: <20190110152148.GE25353@ulmo> References: <1546561418-10230-1-git-send-email-skomatineni@nvidia.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="XuV1QlJbYrcVoo+x" Return-path: Content-Disposition: inline In-Reply-To: <1546561418-10230-1-git-send-email-skomatineni@nvidia.com> Sender: linux-kernel-owner@vger.kernel.org To: Sowjanya Komatineni Cc: jonathanh@nvidia.com, mkarthik@nvidia.com, smohammed@nvidia.com, talho@nvidia.com, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org List-Id: linux-i2c@vger.kernel.org --XuV1QlJbYrcVoo+x Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Jan 03, 2019 at 04:23:38PM -0800, Sowjanya Komatineni wrote: > Bus Clear feature of tegra i2c controller helps to recover from > bus hang when i2c master loses the bus arbitration due to the > slave device holding SDA LOW continuously for some unknown reasons. >=20 > Signed-off-by: Sowjanya Komatineni > --- > drivers/i2c/busses/i2c-tegra.c | 65 ++++++++++++++++++++++++++++++++++++= ++++++ > 1 file changed, 65 insertions(+) >=20 > diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegr= a.c > index 437294ea2f0a..89a0c9fdc99e 100644 > --- a/drivers/i2c/busses/i2c-tegra.c > +++ b/drivers/i2c/busses/i2c-tegra.c > @@ -63,6 +63,7 @@ > #define I2C_FIFO_STATUS_RX_SHIFT 0 > #define I2C_INT_MASK 0x064 > #define I2C_INT_STATUS 0x068 > +#define I2C_INT_BUS_CLR_DONE BIT(11) > #define I2C_INT_PACKET_XFER_COMPLETE BIT(7) > #define I2C_INT_ALL_PACKETS_XFER_COMPLETE BIT(6) > #define I2C_INT_TX_FIFO_OVERFLOW BIT(5) > @@ -105,6 +106,15 @@ > #define I2C_HEADER_MASTER_ADDR_SHIFT 12 > #define I2C_HEADER_SLAVE_ADDR_SHIFT 1 > =20 > +#define I2C_BUS_CLEAR_CNFG 0x084 > +#define I2C_BC_SCLK_THRESHOLD 9 > +#define I2C_BC_SCLK_THRESHOLD_SHIFT 16 > +#define I2C_BC_STOP_COND BIT(2) > +#define I2C_BC_TERMINATE BIT(1) > +#define I2C_BC_ENABLE BIT(0) > +#define I2C_BUS_CLEAR_STATUS 0x088 > +#define I2C_BC_STATUS BIT(0) > + > #define I2C_CONFIG_LOAD 0x08C > #define I2C_MSTR_CONFIG_LOAD BIT(0) > #define I2C_SLV_CONFIG_LOAD BIT(1) > @@ -154,6 +164,8 @@ enum msg_end_type { > * @clk_divisor_std_fast_mode: Clock divisor in standard/fast mode. It is > * applicable if there is no fast clock source i.e. single clock > * source. > + * @has_bus_clr_support: Bus Clear support to recover from bus hang duri= ng > + * SDA stuck low from device for some unknown reasons. Might as well spell out clr as clear in the name. Or maybe to make it shorter, call it supports_bus_clear. > */ > =20 > struct tegra_i2c_hw_feature { > @@ -167,6 +179,7 @@ struct tegra_i2c_hw_feature { > bool has_multi_master_mode; > bool has_slcg_override_reg; > bool has_mst_fifo; > + bool has_bus_clr_support; > }; > =20 > /** > @@ -636,6 +649,9 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_i= d) > goto err; > } > =20 > + if (i2c_dev->hw->has_bus_clr_support && (status & I2C_INT_BUS_CLR_DONE)) > + goto err; > + This looks odd. If we support bus clear and the BUS_CLR_DONE interrupt is set, shouldn't we still process all other potential interrupts? Or was this meant to be inversed: if (!i2c_dev->hw->supports_bus_clear && (status & I2C_INT_BUS_CLR_DONE) ? > if (i2c_dev->msg_read && (status & I2C_INT_RX_FIFO_DATA_REQ)) { > if (i2c_dev->msg_buf_remaining) > tegra_i2c_empty_rx_fifo(i2c_dev); > @@ -664,6 +680,8 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_i= d) > tegra_i2c_mask_irq(i2c_dev, I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST | > I2C_INT_PACKET_XFER_COMPLETE | I2C_INT_TX_FIFO_DATA_REQ | > I2C_INT_RX_FIFO_DATA_REQ); > + if (i2c_dev->hw->has_bus_clr_support) > + tegra_i2c_mask_irq(i2c_dev, I2C_INT_BUS_CLR_DONE); > i2c_writel(i2c_dev, status, I2C_INT_STATUS); > if (i2c_dev->is_dvc) > dvc_writel(i2c_dev, DVC_STATUS_I2C_DONE_INTR, DVC_STATUS); > @@ -674,6 +692,41 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_= id) > return IRQ_HANDLED; > } > =20 > +static int tegra_i2c_issue_bus_clear(struct tegra_i2c_dev *i2c_dev) > +{ > + int time_left, err; > + u32 reg; > + > + if (i2c_dev->hw->has_bus_clr_support) { > + reinit_completion(&i2c_dev->msg_complete); > + reg =3D (I2C_BC_SCLK_THRESHOLD << I2C_BC_SCLK_THRESHOLD_SHIFT) | > + I2C_BC_STOP_COND | I2C_BC_TERMINATE; > + i2c_writel(i2c_dev, reg, I2C_BUS_CLEAR_CNFG); > + if (i2c_dev->hw->has_config_load_reg) { > + err =3D tegra_i2c_wait_for_config_load(i2c_dev); > + if (err) > + return err; > + } > + reg |=3D I2C_BC_ENABLE; > + i2c_writel(i2c_dev, reg, I2C_BUS_CLEAR_CNFG); > + tegra_i2c_unmask_irq(i2c_dev, I2C_INT_BUS_CLR_DONE); > + > + time_left =3D wait_for_completion_timeout(&i2c_dev->msg_complete, > + TEGRA_I2C_TIMEOUT); wait_for_completion_timeout() returns an unsigned long, so the type of time_left should reflect that. 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