[PATCH] dmaengine: tegra: only advertise supported pause operations

[PATCH] dmaengine: tegra: only advertise supported pause operations

[James Hilliard]

Tegra186 does not support pausing a channel, but the driver installs
device_pause and device_resume for every variant. Both callbacks return
-ENOSYS on Tegra186.

dma_get_slave_caps() derives cmd_pause and cmd_resume from the presence
of these callbacks. Clients such as generic 8250 therefore accept RX DMA
channels that cannot satisfy their pause requirement. A receive timeout
then reaches an unsupported pause operation instead of being excluded
when the channel capabilities are checked.

Only install the pause and resume callbacks when the matched chip data
advertises hardware support. Keep them available on Tegra194 and later.

Fixes: ee17028009d4 ("dmaengine: tegra: Add tegra gpcdma driver")
Cc: stable@vger.kernel.org
Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
---
 drivers/dma/tegra186-gpc-dma.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/tegra186-gpc-dma.c b/drivers/dma/tegra186-gpc-dma.c
index e76c58f213d8..72266f490e8a 100644
--- a/drivers/dma/tegra186-gpc-dma.c
+++ b/drivers/dma/tegra186-gpc-dma.c
@@ -1518,8 +1518,10 @@ static int tegra_dma_probe(struct platform_device *pdev)
 	tdma->dma_dev.device_terminate_all = tegra_dma_terminate_all;
 	tdma->dma_dev.device_tx_status = tegra_dma_tx_status;
 	tdma->dma_dev.device_issue_pending = tegra_dma_issue_pending;
-	tdma->dma_dev.device_pause = tegra_dma_device_pause;
-	tdma->dma_dev.device_resume = tegra_dma_device_resume;
+	if (cdata->hw_support_pause) {
+		tdma->dma_dev.device_pause = tegra_dma_device_pause;
+		tdma->dma_dev.device_resume = tegra_dma_device_resume;
+	}
 	tdma->dma_dev.device_synchronize = tegra_dma_chan_synchronize;
 	tdma->dma_dev.residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;
 

---
base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4
change-id: 20261108-submit-tegra186-dma-pause-caps-v1-664d1320d502

Best regards,
--  
James Hilliard <james.hilliard1@gmail.com>

Re: [PATCH] dmaengine: tegra: only advertise supported pause operations

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Low] dmaengine: tegra: redundant pause checks in
  tegra_dma_device_pause()
--

commit 3ce960c2c1d14548e97fac4df9585c921b1d04e0
Author: James Hilliard <james.hilliard1@gmail.com>

dmaengine: tegra: only advertise supported pause operations

This commit registers the device_pause and device_resume callbacks in
tegra_dma_probe() only when cdata->hw_support_pause is set, preventing SoCs
such as Tegra186 from advertising unsupported pause capabilities.

> diff --git a/drivers/dma/tegra186-gpc-dma.c b/drivers/dma/tegra186-gpc-dma.c
> index e76c58f213d84..72266f490e8a3 100644
> --- a/drivers/dma/tegra186-gpc-dma.c
> +++ b/drivers/dma/tegra186-gpc-dma.c
> @@ -1518,8 +1518,10 @@ static int tegra_dma_probe(struct platform_device *pdev)
>  	tdma->dma_dev.device_terminate_all = tegra_dma_terminate_all;
>  	tdma->dma_dev.device_tx_status = tegra_dma_tx_status;
>  	tdma->dma_dev.device_issue_pending = tegra_dma_issue_pending;
> -	tdma->dma_dev.device_pause = tegra_dma_device_pause;
> -	tdma->dma_dev.device_resume = tegra_dma_device_resume;
> +	if (cdata->hw_support_pause) {
> +		tdma->dma_dev.device_pause = tegra_dma_device_pause;
> +		tdma->dma_dev.device_resume = tegra_dma_device_resume;
> +	}

[Severity: Low]
Can the !tdc->tdma->chip_data->hw_support_pause checks in
tegra_dma_device_pause() and tegra_dma_device_resume() be dropped now that
both callbacks are only registered when cdata->hw_support_pause is true?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261108-submit-tegra186-dma-pause-caps-v1-v1-1-9cc9b17a033d@gmail.com?part=1