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Date:   Thu, 5 Sep 2019 20:20:59 +0200
From:   Wolfram Sang <wsa@the-dreams.de>
To:     Lee Jones <lee.jones@linaro.org>
Cc:     alokc@codeaurora.org, agross@kernel.org, robh+dt@kernel.org,
        mark.rutland@arm.com, bjorn.andersson@linaro.org, vkoul@kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-i2c@vger.kernel.org, linux-arm-msm@vger.kernel.org,
        devicetree@vger.kernel.org
Subject: Re: [RESEND v3 1/1] i2c: qcom-geni: Provide an option to disable DMA
 processing
Message-ID: <20190905182058.GA5281@kunai>
References: <20190905144122.5689-1-lee.jones@linaro.org>
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On Thu, Sep 05, 2019 at 03:41:22PM +0100, 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.

$subject is still wrong. And a paragraph that you are/were debugging the
root cause but to no avail so DMA gets disabled for now would be good for a
hotfix this late in the cycle.

>=20
> Signed-off-by: Lee Jones <lee.jones@linaro.org>
> ---
>  drivers/i2c/busses/i2c-qcom-geni.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
>=20
> 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 =3D NULL;
>  	struct geni_se *se =3D &gi2c->se;
>  	size_t len =3D msg->len;
> =20
> -	dma_buf =3D i2c_get_dma_safe_msg_buf(msg, 32);
> +	if (!of_machine_is_compatible("lenovo,yoga-c630"))
> +		dma_buf =3D i2c_get_dma_safe_msg_buf(msg, 32);
> +
>  	if (dma_buf)
>  		geni_se_select_mode(se, GENI_SE_DMA);
>  	else
> @@ -394,11 +396,13 @@ static int geni_i2c_tx_one_msg(struct geni_i2c_dev =
*gi2c, struct i2c_msg *msg,
>  {
>  	dma_addr_t tx_dma;
>  	unsigned long time_left;
> -	void *dma_buf;
> +	void *dma_buf =3D NULL;
>  	struct geni_se *se =3D &gi2c->se;
>  	size_t len =3D msg->len;
> =20
> -	dma_buf =3D i2c_get_dma_safe_msg_buf(msg, 32);
> +	if (!of_machine_is_compatible("lenovo,yoga-c630"))
> +		dma_buf =3D i2c_get_dma_safe_msg_buf(msg, 32);
> +
>  	if (dma_buf)
>  		geni_se_select_mode(se, GENI_SE_DMA);
>  	else
> --=20
> 2.17.1
>=20

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