On Mon, Mar 05, 2018 at 11:17:02AM +0100, Linus Walleij wrote:
> The following happens when connection a DVI output driven
> from the SiI9022 using a DVI-to-VGA adapter plug:
>
> i2c i2c-0: sendbytes: NAK bailout.
> i2c i2c-0: sendbytes: NAK bailout.
>
> Then no picture. Apparently the I2C engine inside the SiI9022
> is not smart enough to try to fall back to DDC I2C. Or the
> vendor have not integrated the electronics properly. I don't
> know which one it is.
>
> After this, the I2C bus seems stalled and the first attempt to
> read the status register fails, and the code returns with
> negative return value, and the display fails to initialized.
>
> Instead, retry status readout five times and continue even
> if this fails.
>
> Tested on the ARM Versatile Express with a DVI-to-VGA
> connector, it now gives picture.
>
> Introduce a helper struct device *dev variable to make
> the code more readable.
>
> Cc: Ville Syrjälä
> Cc: Liviu Dudau
I don't have a suitable configuration to test this, but looks goot to me.
Reviewed-by: Liviu Dudau
BTW, Linus, could it be that your DVI-to-VGA connector doesn't wire
correctly the EDID pin?
Best regards,
Liviu
> Signed-off-by: Linus Walleij
> ---
> ChangeLog v1->v2:
> - Found the real problem instead of trying to explicitly
> shoehorn EDID modes into the error path.
> ---
> drivers/gpu/drm/bridge/sii902x.c | 20
> 1 file changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/sii902x.c
> b/drivers/gpu/drm/bridge/sii902x.c
> index b1ab4ab09532..60373d7eb220 100644
> --- a/drivers/gpu/drm/bridge/sii902x.c
> +++ b/drivers/gpu/drm/bridge/sii902x.c
> @@ -137,7 +137,9 @@ static int sii902x_get_modes(struct drm_connector
> *connector)
> struct sii902x *sii902x = connector_to_sii902x(connector);
> struct regmap *regmap = sii902x->regmap;
> u32 bus_format = MEDIA_BUS_FMT_RGB888_1X24;
> + struct device *dev = &sii902x->i2c->dev;
> unsigned long timeout;
> + unsigned int retries;
> unsigned int status;
> struct edid *edid;
> int num = 0;
> @@ -159,7 +161,7 @@ static int sii902x_get_modes(struct drm_connector
> *connector)
>time_before(jiffies, timeout));
>
> if (!(status & SII902X_SYS_CTRL_DDC_BUS_GRTD)) {
> - dev_err(&sii902x->i2c->dev, "failed to acquire the i2c bus\n");
> + dev_err(dev, "failed to acquire the i2c bus\n");
> return -ETIMEDOUT;
> }
>
> @@ -179,9 +181,19 @@ static int sii902x_get_modes(struct drm_connector
> *connector)
> if (ret)
> return ret;
>
> - ret = regmap_read(regmap, SII902X_SYS_CTRL_DATA, &status);
> + /*
> + * Sometimes the I2C bus can stall after failure to use the
> + * EDID channel. Retry a few times to see if things clear
> + * up, else continue anyway.
> + */
> + retries = 5;
> + do {
> + ret = regmap_read(regmap, SII902X_SYS_CTRL_DATA,
> + &status);
> + retries--;
> + } while (ret && retries);
> if (ret)
> - return ret;
> + dev_err(dev, "failed to read status (%d)\n", ret);
>
> ret = regmap_update_bits(regmap, SII902X_SYS_CTRL_DATA,
>SII902X_SYS_CTRL_DDC_BUS_REQ |
> @@ -201,7 +213,7 @@ static int sii902x_get_modes(struct drm_connector
> *connector)
>
> if (status & (SII902X_SYS_CTRL_DDC_BUS_REQ |
> SII902X_SYS_CTRL_DDC_BUS_GRTD)) {
> - dev_err(&sii902x->i2c->dev, "failed to release the i2c bus\n");
> + dev_err(dev, "failed to release the i2c bus\n");
> return -ETIMEDOUT;
> }
>
> --
> 2.14.3
>
--
| I would like to |
| fix the world, |
| but they're not |
| giving me the |
\ source code! /
---
¯\_(ツ)_/¯
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