linux-kernel - [PATCH] i2c: qcom-geni: make sure I2C hub controllers can't use SE DMA

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Message-Id: <20251029-topic-sm8x50-geni-i2c-hub-no-dma-v1-1-5e264258a5bd@linaro.org>
Date: Wed, 29 Oct 2025 19:07:42 +0100
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Mukesh Kumar Savaliya <mukesh.savaliya@....qualcomm.com>, 
 Viken Dadhaniya <viken.dadhaniya@....qualcomm.com>, 
 Andi Shyti <andi.shyti@...nel.org>, Sumit Semwal <sumit.semwal@...aro.org>, 
 Christian König <christian.koenig@....com>, 
 Wolfram Sang <wsa@...nel.org>, Konrad Dybcio <konradybcio@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, linux-i2c@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-media@...r.kernel.org, 
 dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org, 
 Neil Armstrong <neil.armstrong@...aro.org>
Subject: [PATCH] i2c: qcom-geni: make sure I2C hub controllers can't use SE
 DMA

The I2C Hub controller is a simpler GENI I2C variant that doesn't
support DMA at all, add a no_dma flag to make sure it nevers selects
the SE DMA mode with mappable 32bytes long transfers.

Fixes: cacd9643eca7 ("i2c: qcom-geni: add support for I2C Master Hub variant")
Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
---
 drivers/i2c/busses/i2c-qcom-geni.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
index 43fdd89b8beb..bfb352b04902 100644
--- a/drivers/i2c/busses/i2c-qcom-geni.c
+++ b/drivers/i2c/busses/i2c-qcom-geni.c
@@ -97,6 +97,7 @@ struct geni_i2c_dev {
 	dma_addr_t dma_addr;
 	struct dma_chan *tx_c;
 	struct dma_chan *rx_c;
+	bool no_dma;
 	bool gpi_mode;
 	bool abort_done;
 };
@@ -425,7 +426,7 @@ static int geni_i2c_rx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
 	size_t len = msg->len;
 	struct i2c_msg *cur;
 
-	dma_buf = i2c_get_dma_safe_msg_buf(msg, 32);
+	dma_buf = gi2c->no_dma ? NULL : i2c_get_dma_safe_msg_buf(msg, 32);
 	if (dma_buf)
 		geni_se_select_mode(se, GENI_SE_DMA);
 	else
@@ -464,7 +465,7 @@ static int geni_i2c_tx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
 	size_t len = msg->len;
 	struct i2c_msg *cur;
 
-	dma_buf = i2c_get_dma_safe_msg_buf(msg, 32);
+	dma_buf = gi2c->no_dma ? NULL : i2c_get_dma_safe_msg_buf(msg, 32);
 	if (dma_buf)
 		geni_se_select_mode(se, GENI_SE_DMA);
 	else
@@ -880,10 +881,12 @@ static int geni_i2c_probe(struct platform_device *pdev)
 		goto err_resources;
 	}
 
-	if (desc && desc->no_dma_support)
+	if (desc && desc->no_dma_support) {
 		fifo_disable = false;
-	else
+		gi2c->no_dma = true;
+	} else {
 		fifo_disable = readl_relaxed(gi2c->se.base + GENI_IF_DISABLE_RO) & FIFO_IF_DISABLE;
+	}
 
 	if (fifo_disable) {
 		/* FIFO is disabled, so we can only use GPI DMA */

---
base-commit: dcb6fa37fd7bc9c3d2b066329b0d27dedf8becaa
change-id: 20251029-topic-sm8x50-geni-i2c-hub-no-dma-8812576a65cb

Best regards,
-- 
Neil Armstrong <neil.armstrong@...aro.org>