Quoting Lee Jones (2019-09-05 12:24:12)
> We have a production-level laptop (Lenovo Yoga C630) which is exhibiting
> a rather horrific bug. When I2C HID devices are being scanned for at
> boot-time the QCom Geni based I2C (Serial Engine) attempts to use DMA.
> When it does, the laptop reboots and the user never sees the OS.
>
> Attempts are being made to debug the reason for the spontaneous reboot.
> No luck so far, hence the requirement for this hot-fix. This workaround
> will be removed once we have a viable fix.
>
> Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx>
> ---
> drivers/i2c/busses/i2c-qcom-geni.c | 12 ++++++++----
> 1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
> index a89bfce5388e..17abf60c94ae 100644
> --- a/drivers/i2c/busses/i2c-qcom-geni.c
> +++ b/drivers/i2c/busses/i2c-qcom-geni.c
> @@ -355,11 +355,13 @@ static int geni_i2c_rx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
> {
> dma_addr_t rx_dma;
> unsigned long time_left;
> - void *dma_buf;
> + void *dma_buf = NULL;
> struct geni_se *se = &gi2c->se;
> size_t len = msg->len;
>
> - dma_buf = i2c_get_dma_safe_msg_buf(msg, 32);
> + if (!of_machine_is_compatible("lenovo,yoga-c630"))
This compatible isn't in the 5.3 rc series nor is it in linux-next yet.
Is this "hot-fix" for the next merge window? Or is this compatible
string being generated by firmware somewhere and thus isn't part of the
kernel?
> + dma_buf = i2c_get_dma_safe_msg_buf(msg, 32);
> +
> if (dma_buf)
> geni_se_select_mode(se, GENI_SE_DMA);
> else
