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Wed, 09 Sep 2026 10:54:01 -0700 (PDT) Received: from Empers0n ([193.23.219.104]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49d1fd532dcsm68031755e9.1.2026.09.09.10.53.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Sep 2026 10:54:00 -0700 (PDT) From: Vsevolod Nevorotov To: vkoul@kernel.org, dmaengine@vger.kernel.org Cc: Frank.Li@kernel.org, andi.shyti@kernel.org, mukesh.savaliya@oss.qualcomm.com, naresh.maramaina@oss.qualcomm.com, aniket.randive@oss.qualcomm.com, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, Vsevolod Nevorotov Subject: [PATCH] dmaengine: qcom: gpi: Set IEOB on linked I2C GO TRE to retire TX descriptor Date: Thu, 10 Sep 2026 00:53:32 +0700 Message-ID: <20260909175332.304767-1-sevanevorotov29@gmail.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit In GPI mode, an I2C read transaction consists of a command phase on the TX channel (issuing CONFIG0 and GO TREs) linked to a data phase on the RX channel (issuing the DMA TRE to receive data). Commit 656147fb1d4c ("i2c: qcom-geni: Avoid extra TX DMA TRE for single read message in GPI mode") avoided programming a dummy TX DMA TRE for read messages, leaving only the GO TRE on the TX channel with the TRE_FLAGS_LINK flag set. However, gpi_create_i2c_tre() did not set TRE_FLAGS_IEOB (Interrupt on End of Block) on the linked GO TRE. Because no TRE on the TX channel has an interrupt flag set, GSI hardware never generates a completion event on the TX channel when the GO command finishes. As a result, the TX transfer ring read pointer is never advanced and TX descriptors are never retired. Under sustained or high-frequency traffic (such as touchscreen controllers operating at 120-240 Hz), the TX transfer ring quickly runs out of slots: gpi 900000.dma-controller: not enough space in ring, avail:1 required:3 geni_i2c 990000.i2c: prep_slave_sg failed geni_i2c 990000.i2c: GPI transfer failed: -5 Fix this properly by setting TRE_FLAGS_IEOB on the GO TRE when multi_msg is true (matching Qualcomm's hardware specification and the existing SPI implementation in gpi_create_spi_tre). When the hardware finishes executing the GO command block, it generates an MSM_GPI_TCE_EOB event on the TX channel. In gpi_process_xfer_compl_event(), handle MSM_GPI_TCE_EOB for linked I2C command descriptors without a subsequent TX DMA TRE by retiring the descriptor and updating the cookie without invoking the client callback, allowing the linked RX channel's DMA completion (MSM_GPI_TCE_EOT) to signal final transfer completion to the client. Other EOB events fall through to the default transfer completion path. Fixes: 656147fb1d4c ("i2c: qcom-geni: Avoid extra TX DMA TRE for single read message in GPI mode") Signed-off-by: Vsevolod Nevorotov --- drivers/dma/qcom/gpi.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/drivers/dma/qcom/gpi.c b/drivers/dma/qcom/gpi.c index a5055a6273a..a1ab63bf9f6 100644 --- a/drivers/dma/qcom/gpi.c +++ b/drivers/dma/qcom/gpi.c @@ -1050,6 +1050,13 @@ static void gpi_process_xfer_compl_event(struct gchan *gchan, return; } + if (compl_event->code == MSM_GPI_TCE_EOB && + gchan->protocol == QCOM_GPI_I2C && + (gpi_desc->tre[gpi_desc->num_tre - 1].dword[3] & TRE_FLAGS_LINK)) { + dma_cookie_complete(&vd->tx); + goto gpi_free_desc; + } + if (compl_event->code == MSM_GPI_TCE_UNEXP_ERR) { dev_err(gpii->gpi_dev->dev, "Error in Transaction\n"); result.result = DMA_TRANS_ABORTED; @@ -1668,10 +1675,12 @@ static int gpi_create_i2c_tre(struct gchan *chan, struct gpi_desc *desc, tre->dword[3] = u32_encode_bits(TRE_TYPE_GO, TRE_FLAGS_TYPE); - if (i2c->multi_msg) + if (i2c->multi_msg) { + tre->dword[3] |= u32_encode_bits(1, TRE_FLAGS_IEOB); tre->dword[3] |= u32_encode_bits(1, TRE_FLAGS_LINK); - else + } else { tre->dword[3] |= u32_encode_bits(1, TRE_FLAGS_CHAIN); + } } if (i2c->op == I2C_READ || i2c->multi_msg == false) { -- 2.55.0