Hi Alex,
On Thu, 14 Apr 2011 19:47:06 -0400, Alex Deucher wrote:
> Apparently some distros set i2c-algo-bit.bit_test to 1 by
> default. In some cases this causes i2c_bit_add_bus
> to fail and prevents the i2c bus from being added. In the
> radeon case, we fail to add the ddc i2c buses which prevents
> the driver from being able to detect attached monitors.
> The i2c bus works fine even if bit_test fails. This is likely
> due to gpio switching that is required and handled in the
> pre/post_xfer hooks, so call the pre/post_xfer hooks in the
> bit test as well.
>
> Fixes:
> https://bugs.freedesktop.org/show_bug.cgi?id=36221
>
> Cc: Jean Delvare <kh...@linux-fr.org>
> Signed-off-by: Alex Deucher <alexdeuc...@gmail.com>
Good catch, applied, thanks. I'll also push this to the stable kernel
trees (from .38 down to .34.)
> ---
> drivers/i2c/algos/i2c-algo-bit.c | 21 ++++++++++++++++++---
> 1 files changed, 18 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/i2c/algos/i2c-algo-bit.c
> b/drivers/i2c/algos/i2c-algo-bit.c
> index 38319a6..e2740e6 100644
> --- a/drivers/i2c/algos/i2c-algo-bit.c
> +++ b/drivers/i2c/algos/i2c-algo-bit.c
> @@ -232,9 +232,16 @@ static int i2c_inb(struct i2c_adapter *i2c_adap)
> * Sanity check for the adapter hardware - check the reaction of
> * the bus lines only if it seems to be idle.
> */
> -static int test_bus(struct i2c_algo_bit_data *adap, char *name)
> +static int test_bus(struct i2c_adapter *i2c_adap, char *name)
> {
> - int scl, sda;
> + struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
> + int scl, sda, ret;
> +
> + if (adap->pre_xfer) {
> + ret = adap->pre_xfer(i2c_adap);
> + if (ret < 0)
> + return -ENODEV;
> + }
>
> if (adap->getscl == NULL)
> pr_info("%s: Testing SDA only, SCL is not readable\n", name);
> @@ -297,11 +304,19 @@ static int test_bus(struct i2c_algo_bit_data *adap,
> char *name)
> "while pulling SCL high!\n", name);
> goto bailout;
> }
> +
> + if (adap->post_xfer)
> + adap->post_xfer(i2c_adap);
> +
> pr_info("%s: Test OK\n", name);
> return 0;
> bailout:
> sdahi(adap);
> sclhi(adap);
> +
> + if (adap->post_xfer)
> + adap->post_xfer(i2c_adap);
> +
> return -ENODEV;
> }
>
> @@ -607,7 +622,7 @@ static int __i2c_bit_add_bus(struct i2c_adapter *adap,
> int ret;
>
> if (bit_test) {
> - ret = test_bus(bit_adap, adap->name);
> + ret = test_bus(adap, adap->name);
> if (ret < 0)
> return -ENODEV;
> }
--
Jean Delvare
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