linux-kernel - [RESEND v3 1/1] i2c: qcom-geni: Provide an option to disable DMA processing

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Date:   Thu,  5 Sep 2019 15:41:22 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     alokc@...eaurora.org, agross@...nel.org, robh+dt@...nel.org,
        mark.rutland@....com, bjorn.andersson@...aro.org, vkoul@...nel.org,
        wsa@...-dreams.de
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-i2c@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, Lee Jones <lee.jones@...aro.org>
Subject: [RESEND v3 1/1] i2c: qcom-geni: Provide an option to disable DMA processing

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.

Signed-off-by: Lee Jones <lee.jones@...aro.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
-- 
2.17.1