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X-Patchwork-Submitter: Lee Jones <lee.jones@linaro.org>
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From: Lee Jones <lee.jones@linaro.org>
To: alokc@codeaurora.org, agross@kernel.org, robh+dt@kernel.org,
        mark.rutland@arm.com, bjorn.andersson@linaro.org, vkoul@kernel.org,
        wsa@the-dreams.de
Cc: linux-i2c@vger.kernel.org, linux-arm-msm@vger.kernel.org,
        devicetree@vger.kernel.org, Lee Jones <lee.jones@linaro.org>
Subject: [RESEND v3 1/1] i2c: qcom-geni: Disable DMA processing on the Lenovo
 Yoga C630
Date: Thu,  5 Sep 2019 20:24:12 +0100
Message-Id: <20190905192412.23116-1-lee.jones@linaro.org>
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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@linaro.org>
---
 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"))
+		dma_buf = 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 = 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"))
+		dma_buf = i2c_get_dma_safe_msg_buf(msg, 32);
+
 	if (dma_buf)
 		geni_se_select_mode(se, GENI_SE_DMA);
 	else