From: Thomas Andreatta thomasandreatta2000@gmail.com
[ Upstream commit d9a3e9929452780df16f3414f0d59b5f69d058cf ]
This patch modifies the type of setup_xref from void to int and handles errors since the function can fail.
`setup_xref` now returns the (eventual) error from `dmae_set_dmars`|`dmae_set_chcr`, while `shdma_tx_submit` handles the result, removing the chunks from the queue and marking PM as idle in case of an error.
Signed-off-by: Thomas Andreatta thomas.andreatta2000@gmail.com Link: https://lore.kernel.org/r/20250827152442.90962-1-thomas.andreatta2000@gmail.... Signed-off-by: Vinod Koul vkoul@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org ---
LLM Generated explanations, may be completely bogus:
YES
- What it fixes - Previously, `sh_dmae_setup_xfer()` unconditionally programmed DMARS/CHCR and ignored failures, so if the channel was busy (e.g., `dmae_is_busy()`), programming would silently fail. The engine then proceeded as if configured, risking misconfigured or stalled transfers. The former code path and even an in-code TODO acknowledged this gap (see drivers/dma/sh/shdma-base.c:70, prior to this change). - This patch converts `.setup_xfer` to return an `int`, propagates errors from `dmae_set_dmars()` and `dmae_set_chcr()`, and makes `shdma_tx_submit()` unwind cleanly on failure.
- Key changes (small and contained) - drivers/dma/sh/shdma-base.c:133 - Now checks the return of `ops->setup_xfer(schan, schan->slave_id)`. On error, it: - Logs the error. - Removes all chunks for this transaction from `ld_queue` and marks them `DESC_IDLE` (drivers/dma/sh/shdma-base.c:137–143). - Balances runtime PM by calling `pm_runtime_put()` (drivers/dma/sh/shdma-base.c:145–147). - Returns a negative error code via `tx_submit`, which is supported by the DMAengine API (`dma_submit_error(cookie)`). - drivers/dma/sh/shdmac.c:303 - `sh_dmae_setup_xfer()` now returns `int`. It propagates failures from: - `dmae_set_dmars(sh_chan, cfg->mid_rid)` (drivers/dma/sh/shdmac.c:313–315). - `dmae_set_chcr(sh_chan, cfg->chcr)` (drivers/dma/sh/shdmac.c:317–319). - For MEMCPY (`slave_id < 0`), it still calls `dmae_init(sh_chan)` with no error (drivers/dma/sh/shdmac.c:321–323). - include/linux/shdma-base.h:99 - `struct shdma_ops` changes `setup_xfer` from `void (*setup_xfer)(...)` to `int (*setup_xfer)(...)`, enabling error propagation while remaining internal to the SH DMAC driver family.
- Why it fits stable criteria - Bug fix that affects users: prevents silent misconfiguration when programming fails due to a busy channel, a real condition indicated by the underlying helpers (`dmae_set_dmars`/`dmae_set_chcr`). - Minimal and localized: confined to the SH DMA engine base and implementation; only one implementer of `shdma_ops->setup_xfer` exists (drivers/dma/sh/shdmac.c:662 for the ops table), so the API change is self-contained. - Low regression risk: - `tx_submit` returning negative errors is standard; clients typically check with `dma_submit_error(cookie)`. - On error, descriptors are unqueued and returned to `ld_free`, and runtime PM is balanced; no dangling state. - No functional change on success paths; MEMCPY path unchanged except for return value plumbing. - No architectural changes or feature additions; this is targeted error handling and cleanup. - Touches a driver-level subsystem, not core kernel frameworks.
- Side-effects considered - Behavior now fails fast instead of silently proceeding on hardware programming failure; this is an intended correctness improvement. - Header change is internal to the SH DMAC base and its only in-tree user; it should not impact other DMA drivers.
Overall, this is a straightforward, self-contained bug fix that improves robustness and correctness with minimal risk, making it a good candidate for stable backport.
drivers/dma/sh/shdma-base.c | 25 +++++++++++++++++++------ drivers/dma/sh/shdmac.c | 17 +++++++++++++---- include/linux/shdma-base.h | 2 +- 3 files changed, 33 insertions(+), 11 deletions(-)
diff --git a/drivers/dma/sh/shdma-base.c b/drivers/dma/sh/shdma-base.c index 6b4fce453c85c..834741adadaad 100644 --- a/drivers/dma/sh/shdma-base.c +++ b/drivers/dma/sh/shdma-base.c @@ -129,12 +129,25 @@ static dma_cookie_t shdma_tx_submit(struct dma_async_tx_descriptor *tx) const struct shdma_ops *ops = sdev->ops; dev_dbg(schan->dev, "Bring up channel %d\n", schan->id); - /* - * TODO: .xfer_setup() might fail on some platforms. - * Make it int then, on error remove chunks from the - * queue again - */ - ops->setup_xfer(schan, schan->slave_id); + + ret = ops->setup_xfer(schan, schan->slave_id); + if (ret < 0) { + dev_err(schan->dev, "setup_xfer failed: %d\n", ret); + + /* Remove chunks from the queue and mark them as idle */ + list_for_each_entry_safe(chunk, c, &schan->ld_queue, node) { + if (chunk->cookie == cookie) { + chunk->mark = DESC_IDLE; + list_move(&chunk->node, &schan->ld_free); + } + } + + schan->pm_state = SHDMA_PM_ESTABLISHED; + ret = pm_runtime_put(schan->dev); + + spin_unlock_irq(&schan->chan_lock); + return ret; + }
if (schan->pm_state == SHDMA_PM_PENDING) shdma_chan_xfer_ld_queue(schan); diff --git a/drivers/dma/sh/shdmac.c b/drivers/dma/sh/shdmac.c index 093e449e19eee..603e15102e45e 100644 --- a/drivers/dma/sh/shdmac.c +++ b/drivers/dma/sh/shdmac.c @@ -300,21 +300,30 @@ static bool sh_dmae_channel_busy(struct shdma_chan *schan) return dmae_is_busy(sh_chan); }
-static void sh_dmae_setup_xfer(struct shdma_chan *schan, - int slave_id) +static int sh_dmae_setup_xfer(struct shdma_chan *schan, int slave_id) { struct sh_dmae_chan *sh_chan = container_of(schan, struct sh_dmae_chan, shdma_chan);
+ int ret = 0; if (slave_id >= 0) { const struct sh_dmae_slave_config *cfg = sh_chan->config;
- dmae_set_dmars(sh_chan, cfg->mid_rid); - dmae_set_chcr(sh_chan, cfg->chcr); + ret = dmae_set_dmars(sh_chan, cfg->mid_rid); + if (ret < 0) + goto END; + + ret = dmae_set_chcr(sh_chan, cfg->chcr); + if (ret < 0) + goto END; + } else { dmae_init(sh_chan); } + +END: + return ret; }
/* diff --git a/include/linux/shdma-base.h b/include/linux/shdma-base.h index 6dfd05ef5c2d9..03ba4dab2ef73 100644 --- a/include/linux/shdma-base.h +++ b/include/linux/shdma-base.h @@ -96,7 +96,7 @@ struct shdma_ops { int (*desc_setup)(struct shdma_chan *, struct shdma_desc *, dma_addr_t, dma_addr_t, size_t *); int (*set_slave)(struct shdma_chan *, int, dma_addr_t, bool); - void (*setup_xfer)(struct shdma_chan *, int); + int (*setup_xfer)(struct shdma_chan *, int); void (*start_xfer)(struct shdma_chan *, struct shdma_desc *); struct shdma_desc *(*embedded_desc)(void *, int); bool (*chan_irq)(struct shdma_chan *, int);