Re: [PATCH v4 01/17] dmaengine: sh: rz-dmac: Move interrupt request after everything is set up
From: Claudiu Beznea
Date: Sat Apr 11 2026 - 08:34:27 EST
On 4/11/26 15:17, Biju Das wrote:
-----Original Message-----As per [1], it is redundant.
From: Claudiu<claudiu.beznea@xxxxxxxxx>
Sent: 11 April 2026 12:43
Subject: [PATCH v4 01/17] dmaengine: sh: rz-dmac: Move interrupt request after everything is set up
From: Claudiu Beznea<claudiu.beznea.uj@xxxxxxxxxxxxxx>
Once the interrupt is requested, the interrupt handler may run immediately.
Since the IRQ handler can access channel->ch_base, which is initialized only after requesting the IRQ,
this may lead to invalid memory access.
Likewise, the IRQ thread may access uninitialized data (the ld_free, ld_queue, and ld_active lists),
which may also lead to issues.
Request the interrupts only after everything is set up. To keep the error path simpler, use
dmam_alloc_coherent() instead of dma_alloc_coherent().
Fixes: 5000d37042a6 ("dmaengine: sh: Add DMAC driver for RZ/G2L SoC")
Cc:stable@xxxxxxxxxxxxxxx
Signed-off-by: Claudiu Beznea<claudiu.beznea.uj@xxxxxxxxxxxxxx>
---
Changes in v4:
- none, this patch is new
drivers/dma/sh/rz-dmac.c | 88 +++++++++++++++-------------------------
1 file changed, 33 insertions(+), 55 deletions(-)
diff --git a/drivers/dma/sh/rz-dmac.c b/drivers/dma/sh/rz-dmac.c index 625ff29024de..9f206a33dcc6
100644
--- a/drivers/dma/sh/rz-dmac.c
+++ b/drivers/dma/sh/rz-dmac.c
@@ -981,25 +981,6 @@ static int rz_dmac_chan_probe(struct rz_dmac *dmac,
channel->index = index;
channel->mid_rid = -EINVAL;
- /* Request the channel interrupt. */
- scnprintf(pdev_irqname, sizeof(pdev_irqname), "ch%u", index);
- irq = platform_get_irq_byname(pdev, pdev_irqname);
- if (irq < 0)
- return irq;
-
- irqname = devm_kasprintf(dmac->dev, GFP_KERNEL, "%s:%u",
- dev_name(dmac->dev), index);
- if (!irqname)
- return -ENOMEM;
-
- ret = devm_request_threaded_irq(dmac->dev, irq, rz_dmac_irq_handler,
- rz_dmac_irq_handler_thread, 0,
- irqname, channel);
- if (ret) {
- dev_err(dmac->dev, "failed to request IRQ %u (%d)\n", irq, ret);
- return ret;
- }
-
/* Set io base address for each channel */
if (index < 8) {
channel->ch_base = dmac->base + CHANNEL_0_7_OFFSET + @@ -1012,9 +993,9 @@ static int
rz_dmac_chan_probe(struct rz_dmac *dmac,
}
/* Allocate descriptors */
- lmdesc = dma_alloc_coherent(&pdev->dev,
- sizeof(struct rz_lmdesc) * DMAC_NR_LMDESC,
- &channel->lmdesc.base_dma, GFP_KERNEL);
+ lmdesc = dmam_alloc_coherent(&pdev->dev,
+ sizeof(struct rz_lmdesc) * DMAC_NR_LMDESC,
+ &channel->lmdesc.base_dma, GFP_KERNEL);
if (!lmdesc) {
dev_err(&pdev->dev, "Can't allocate memory (lmdesc)\n");
return -ENOMEM;
@@ -1030,7 +1011,24 @@ static int rz_dmac_chan_probe(struct rz_dmac *dmac,
INIT_LIST_HEAD(&channel->ld_free);
INIT_LIST_HEAD(&channel->ld_active);
- return 0;
+ /* Request the channel interrupt. */
+ scnprintf(pdev_irqname, sizeof(pdev_irqname), "ch%u", index);
+ irq = platform_get_irq_byname(pdev, pdev_irqname);
+ if (irq < 0)
+ return irq;
+
+ irqname = devm_kasprintf(dmac->dev, GFP_KERNEL, "%s:%u",
+ dev_name(dmac->dev), index);
+ if (!irqname)
+ return -ENOMEM;
+
+ ret = devm_request_threaded_irq(dmac->dev, irq, rz_dmac_irq_handler,
+ rz_dmac_irq_handler_thread, 0,
+ irqname, channel);
+ if (ret)
+ dev_err(dmac->dev, "failed to request IRQ %u (%d)\n", irq, ret);
[1]
https://elixir.bootlin.com/linux/v7.0-rc7/source/kernel/irq/devres.c#L108
This is a fix patch, it just moves code around, intended to be backported to older kernels (e.g. v6.1, v6.12). However devm_request_result() is introduced in:
commit 55b48e23f5c4
Author: Pan Chuang <panchuang@xxxxxxxx>
Date: Tue Aug 5 17:29:22 2025 +0800
genirq/devres: Add error handling in devm_request_*_irq()
devm_request_threaded_irq() and devm_request_any_context_irq() currently
don't print any error message when interrupt registration fails.
This forces each driver to implement redundant error logging - over 2,000
lines of error messages exist across drivers. Additionally, when
upper-layer functions propagate these errors without logging, critical
debugging information is lost.
Add devm_request_result() helper to unify error reporting via dev_err_probe(),
Use it in devm_request_threaded_irq() and devm_request_any_context_irq()
printing device name, IRQ number, handler functions, and error code on failure
automatically.
Co-developed-by: Yangtao Li <frank.li@xxxxxxxx>
Signed-off-by: Yangtao Li <frank.li@xxxxxxxx>
Signed-off-by: Pan Chuang <panchuang@xxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/all/20250805092922.135500-2-panchuang@xxxxxxxx
And it is not present in v6.1, v6.12 kernels.
To have a clean backport (at least to the above mentioned kernel versions), would be better to have the alignment to devm_request_result() done in a later cleanup patch.
Thank you,
Claudiu