On Thu, 05 Sep 2019, Marc Gonzalez wrote:
> [ Trimming recipients list for idle chat ]
>
> On 05/09/2019 09:52, Lee Jones wrote:
>
> > 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.
> >
> > The beautiful thing about this approach is that, *if* the Geni SE DMA
> > ever starts working, we can remove the C code and any old properties
> > left in older DTs just become NOOP. Older kernels with newer DTs (less
> > of a priority) *still* will not work - but they do not work now anyway.
> >
> > Fixes: 8bc529b25354 ("soc: qcom: geni: Add support for ACPI")
> > Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx>
> > Reviewed-by: Vinod Koul <vkoul@xxxxxxxxxx>
> > ---
> > drivers/i2c/busses/i2c-qcom-geni.c | 14 ++++++++++----
> > 1 file changed, 10 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
> > index a89bfce5388e..8822dea82980 100644
> > --- a/drivers/i2c/busses/i2c-qcom-geni.c
> > +++ b/drivers/i2c/busses/i2c-qcom-geni.c
> > @@ -353,13 +353,16 @@ static void geni_i2c_tx_fsm_rst(struct geni_i2c_dev *gi2c)
> > static int geni_i2c_rx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
> > u32 m_param)
> > {
> > + struct device_node *np = gi2c->se.dev->of_node;
> > 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_property_read_bool(np, "qcom,geni-se-no-dma"))
> > + dma_buf = i2c_get_dma_safe_msg_buf(msg, 32);
> > +
> > if (dma_buf)
> > geni_se_select_mode(se, GENI_SE_DMA);
> > else
> > @@ -392,13 +395,16 @@ static int geni_i2c_rx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
> > static int geni_i2c_tx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
> > u32 m_param)
> > {
> > + struct device_node *np = gi2c->se.dev->of_node;
> > dma_addr_t tx_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_property_read_bool(np, "qcom,geni-se-no-dma"))
> > + dma_buf = i2c_get_dma_safe_msg_buf(msg, 32);
> > +
> > if (dma_buf)
> > geni_se_select_mode(se, GENI_SE_DMA);
> > else
> >
>
> Would it make sense to factorize the DT lookup within a helper?
> (For example; not compile-tested; not sure it's worth it)
Possibly, but the semantics end up the same.
If you think it's cleaner, perhaps submit your version a fix-up to the
original (this one). Seeing as we're already carrying Reviewed-bys
and time is very limited to have this fixed.
I would also like to see the helper in your version prefixed, so it
would be:
geni_i2c_get_dma_buf()
> diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
> index a89bfce5388e..1489181f60fe 100644
> --- a/drivers/i2c/busses/i2c-qcom-geni.c
> +++ b/drivers/i2c/busses/i2c-qcom-geni.c
> @@ -350,6 +350,14 @@ static void geni_i2c_tx_fsm_rst(struct geni_i2c_dev *gi2c)
> dev_err(gi2c->se.dev, "Timeout resetting TX_FSM\n");
> }
>
> +static void *get_dma_buf(struct geni_se *se, struct i2c_msg *msg)
> +{
> + if (of_property_read_bool(se->dev->of_node, "qcom,geni-se-no-dma"))
> + return NULL;
> +
> + return i2c_get_dma_safe_msg_buf(msg, 32);
> +}
> +
> static int geni_i2c_rx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
> u32 m_param)
> {
> @@ -359,7 +367,7 @@ static int geni_i2c_rx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
> struct geni_se *se = &gi2c->se;
> size_t len = msg->len;
>
> - dma_buf = i2c_get_dma_safe_msg_buf(msg, 32);
> + dma_buf = get_dma_buf(se, msg);
> if (dma_buf)
> geni_se_select_mode(se, GENI_SE_DMA);
> else
> @@ -398,7 +406,7 @@ static int geni_i2c_tx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
> struct geni_se *se = &gi2c->se;
> size_t len = msg->len;
>
> - dma_buf = i2c_get_dma_safe_msg_buf(msg, 32);
> + dma_buf = get_dma_buf(se, msg);
> if (dma_buf)
> geni_se_select_mode(se, GENI_SE_DMA);
> else
--
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
