| Message ID | 20201006105135.28985-2-ceggers@arri.de |
|---|---|
| State | Superseded |
| Headers | show |
| Series | i2c: imx: Fix handling of arbitration loss | expand |
From: Christian Eggers > Sent: 06 October 2020 11:52 > > According to the "VFxxx Controller Reference Manual" (and the comment > block starting at line 97), Vybrid requires writing a one for clearing > an interrupt flag. Syncing the method for clearing I2SR_IIF in > i2c_imx_isr(). > > Signed-off-by: Christian Eggers <ceggers@arri.de> > Cc: stable@vger.kernel.org > --- > drivers/i2c/busses/i2c-imx.c | 20 +++++++++++++++----- > 1 file changed, 15 insertions(+), 5 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c > index 0ab5381aa012..745f4071155a 100644 > --- a/drivers/i2c/busses/i2c-imx.c > +++ b/drivers/i2c/busses/i2c-imx.c > @@ -412,6 +412,19 @@ static void i2c_imx_dma_free(struct imx_i2c_struct *i2c_imx) > dma->chan_using = NULL; > } > > +static void i2c_imx_clear_irq(struct imx_i2c_struct *i2c_imx, unsigned int bits) > +{ > + unsigned int temp; > + > + /* > + * i2sr_clr_opcode is the value to clear all interrupts. > + * Here we want to clear only <bits>, so we write > + * ~i2sr_clr_opcode with just <bits> toggled. > + */ > + temp = ~i2c_imx->hwdata->i2sr_clr_opcode ^ bits; > + imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2SR); > +} That looks either wrong or maybe just overcomplicated. Why isn't: imx_i2c_write_reg(bits, i2c_imx, IMX_I2C_I2SR); enough? More usually you just write back the read value of such 'write 1 to clear' status registers and then act on all the set bits. That ensures you clear all interrupts that were pending. If you need to avoid writes of bits that aren't in the 'clear all interrupts' value then you just need: bits &= i2c_imx->hwdata->i2sr_clr_opcode; prior to the write. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
On Tue, Oct 06, 2020 at 12:06:36PM +0000, David Laight wrote: > From: Christian Eggers > > Sent: 06 October 2020 11:52 > > > > According to the "VFxxx Controller Reference Manual" (and the comment > > block starting at line 97), Vybrid requires writing a one for clearing > > an interrupt flag. Syncing the method for clearing I2SR_IIF in > > i2c_imx_isr(). > > > > Signed-off-by: Christian Eggers <ceggers@arri.de> > > Cc: stable@vger.kernel.org > > --- > > drivers/i2c/busses/i2c-imx.c | 20 +++++++++++++++----- > > 1 file changed, 15 insertions(+), 5 deletions(-) > > > > diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c > > index 0ab5381aa012..745f4071155a 100644 > > --- a/drivers/i2c/busses/i2c-imx.c > > +++ b/drivers/i2c/busses/i2c-imx.c > > @@ -412,6 +412,19 @@ static void i2c_imx_dma_free(struct imx_i2c_struct *i2c_imx) > > dma->chan_using = NULL; > > } > > > > +static void i2c_imx_clear_irq(struct imx_i2c_struct *i2c_imx, unsigned int bits) > > +{ > > + unsigned int temp; > > + > > + /* > > + * i2sr_clr_opcode is the value to clear all interrupts. > > + * Here we want to clear only <bits>, so we write > > + * ~i2sr_clr_opcode with just <bits> toggled. > > + */ > > + temp = ~i2c_imx->hwdata->i2sr_clr_opcode ^ bits; > > + imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2SR); > > +} > > That looks either wrong or maybe just overcomplicated. > Why isn't: > imx_i2c_write_reg(bits, i2c_imx, IMX_I2C_I2SR); > enough? Your question suggests you either didn't read the comment or the comment is not good enough. Maybe once you understood the complication (see Christian's mail) you could suggest a better wording? Maybe we have to mention that this handles both W1C and W0C. Best regards Uwe
diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c index 0ab5381aa012..745f4071155a 100644 --- a/drivers/i2c/busses/i2c-imx.c +++ b/drivers/i2c/busses/i2c-imx.c @@ -412,6 +412,19 @@ static void i2c_imx_dma_free(struct imx_i2c_struct *i2c_imx) dma->chan_using = NULL; } +static void i2c_imx_clear_irq(struct imx_i2c_struct *i2c_imx, unsigned int bits) +{ + unsigned int temp; + + /* + * i2sr_clr_opcode is the value to clear all interrupts. + * Here we want to clear only <bits>, so we write + * ~i2sr_clr_opcode with just <bits> toggled. + */ + temp = ~i2c_imx->hwdata->i2sr_clr_opcode ^ bits; + imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2SR); +} + static int i2c_imx_bus_busy(struct imx_i2c_struct *i2c_imx, int for_busy, bool atomic) { unsigned long orig_jiffies = jiffies; @@ -424,8 +437,7 @@ static int i2c_imx_bus_busy(struct imx_i2c_struct *i2c_imx, int for_busy, bool a /* check for arbitration lost */ if (temp & I2SR_IAL) { - temp &= ~I2SR_IAL; - imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2SR); + i2c_imx_clear_irq(i2c_imx, I2SR_IAL); return -EAGAIN; } @@ -623,9 +635,7 @@ static irqreturn_t i2c_imx_isr(int irq, void *dev_id) if (temp & I2SR_IIF) { /* save status register */ i2c_imx->i2csr = temp; - temp &= ~I2SR_IIF; - temp |= (i2c_imx->hwdata->i2sr_clr_opcode & I2SR_IIF); - imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2SR); + i2c_imx_clear_irq(i2c_imx, I2SR_IIF); wake_up(&i2c_imx->queue); return IRQ_HANDLED; }
According to the "VFxxx Controller Reference Manual" (and the comment block starting at line 97), Vybrid requires writing a one for clearing an interrupt flag. Syncing the method for clearing I2SR_IIF in i2c_imx_isr(). Signed-off-by: Christian Eggers <ceggers@arri.de> Cc: stable@vger.kernel.org --- drivers/i2c/busses/i2c-imx.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-)