iommu: ipmmu-vmsa: Add DMA controllers to devices_allowlist

[PATCH] iommu: ipmmu-vmsa: Add DMA controllers to devices_allowlist

Posted by Koichiro Den 3 months, 1 week ago

Add Renesas DMA controller devices to the devices_allowlist to enable
their use with the IPMMU. This allows DMA channels to operate through
the IOMMU when enabled.

Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
 drivers/iommu/ipmmu-vmsa.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/ipmmu-vmsa.c b/drivers/iommu/ipmmu-vmsa.c
index ffa892f65714..88c4fb6424ed 100644
--- a/drivers/iommu/ipmmu-vmsa.c
+++ b/drivers/iommu/ipmmu-vmsa.c
@@ -741,7 +741,9 @@ static const char * const devices_allowlist[] = {
 	"ee100000.mmc",
 	"ee120000.mmc",
 	"ee140000.mmc",
-	"ee160000.mmc"
+	"ee160000.mmc",
+	"e7350000.dma-controller",
+	"e7351000.dma-controller"
 };
 
 static bool ipmmu_device_is_allowed(struct device *dev)
-- 
2.48.1

Re: [PATCH] iommu: ipmmu-vmsa: Add DMA controllers to devices_allowlist

Posted by Geert Uytterhoeven 3 months, 1 week ago

Hi Den-san,

On Mon, 27 Oct 2025 at 02:26, Koichiro Den <den@valinux.co.jp> wrote:
> Add Renesas DMA controller devices to the devices_allowlist to enable
> their use with the IPMMU. This allows DMA channels to operate through
> the IOMMU when enabled.
>
> Signed-off-by: Koichiro Den <den@valinux.co.jp>

Thanks for your patch!

> --- a/drivers/iommu/ipmmu-vmsa.c
> +++ b/drivers/iommu/ipmmu-vmsa.c
> @@ -741,7 +741,9 @@ static const char * const devices_allowlist[] = {
>         "ee100000.mmc",
>         "ee120000.mmc",
>         "ee140000.mmc",
> -       "ee160000.mmc"
> +       "ee160000.mmc",
> +       "e7350000.dma-controller",
> +       "e7351000.dma-controller"

While your change looks correct to me, it causes DMA mapping failures on
Gray Hawk Single and Sparrow Hawk when IPMMU support is enabled
(on renesas-drivers-2025-10-28-v6.18-rc3 with renesas_defconfig
+ CONFIG_IPMMU_VMSA=y):

    rcar-dmac e7351000.dma-controller: chan1: failed to map 1@0x00000000e656000c
    sh-sci e6560000.serial: Failed preparing Tx DMA descriptor

0xe656000c = HSCIF2 Transmit FIFO data register.

With "#define DEBUG" added to drivers/dma/sh/rcar-dmac.c:

    rcar-dmac e7351000.dma-controller: chan1: failed to map 1@0x00000000e656000c
    sh-sci e6560000.serial: Failed preparing Tx DMA descriptor
    rcar-dmac e7351000.dma-controller: chan2: map 1@0x00000000e6560014
to 0x00000000fff82014 dir: DMA_TO_DEVICE
    rcar-dmac e7351000.dma-controller: chan2: chunk
00000000e5110c20/000000005e0ede90 sgl 0@000000000d8c5440, 256/256
0x00000000fff82014 -> 0x00000000ffed6000
    rcar-dmac e7351000.dma-controller: chan2: submit #2@000000005e0ede90
    rcar-dmac e7351000.dma-controller: chan2: chunk
0000000025f2f66c/00000000e5f0dd15 sgl 0@0000000064f1067f, 256/256
0x00000000fff82014 -> 0x00000000ffed6100
    rcar-dmac e7351000.dma-controller: chan2: submit #3@00000000e5f0dd15
    rcar-dmac e7351000.dma-controller: chan2: queue chunk
00000000e5110c20: 256@0x00000000fff82014 -> 0x00000000ffed6000

0xe6560014 = HSCIF2 Receive FIFO data register

Comparing to the CONFIG_IPMMU_VMSA=n case:

    rcar-dmac e7351000.dma-controller: chan1: map 1@0x00000000e656000c
to 0x00000000e656000c dir: DMA_FROM_DEVICE
    rcar-dmac e7351000.dma-controller: chan1: chunk
0000000096396eb4/00000000f35357b6 sgl 0@0000000013546bf6, 74/74
0x0000000489ab5000 -> 0x00000000e656000c
    rcar-dmac e7351000.dma-controller: chan1: submit #2@00000000f35357b6
    rcar-dmac e7351000.dma-controller: chan1: queue chunk
0000000096396eb4: 74@0x0000000489ab5000 -> 0x00000000e656000c

This confuses me even more: why no DMA_TO_DEVICE mapping in the
latter case?

>  };
>
>  static bool ipmmu_device_is_allowed(struct device *dev)

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH] iommu: ipmmu-vmsa: Add DMA controllers to devices_allowlist

Posted by Ryo Takakura 3 months ago

Hi, Geert!

I'm helping out Den-san a bit on the issue.

On Wed, 29 Oct 2025 17:08:07 +0100, Geert Uytterhoeven wrote:
>On Mon, 27 Oct 2025 at 02:26, Koichiro Den <den@valinux.co.jp> wrote:
>> Add Renesas DMA controller devices to the devices_allowlist to enable
>> their use with the IPMMU. This allows DMA channels to operate through
>> the IOMMU when enabled.
>>
>> Signed-off-by: Koichiro Den <den@valinux.co.jp>
>
>Thanks for your patch!
>
>> --- a/drivers/iommu/ipmmu-vmsa.c
>> +++ b/drivers/iommu/ipmmu-vmsa.c
>> @@ -741,7 +741,9 @@ static const char * const devices_allowlist[] = {
>>         "ee100000.mmc",
>>         "ee120000.mmc",
>>         "ee140000.mmc",
>> -       "ee160000.mmc"
>> +       "ee160000.mmc",
>> +       "e7350000.dma-controller",
>> +       "e7351000.dma-controller"
>
>While your change looks correct to me, it causes DMA mapping failures on
>Gray Hawk Single and Sparrow Hawk when IPMMU support is enabled
>(on renesas-drivers-2025-10-28-v6.18-rc3 with renesas_defconfig
>+ CONFIG_IPMMU_VMSA=y):
>
>    rcar-dmac e7351000.dma-controller: chan1: failed to map 1@0x00000000e656000c
>    sh-sci e6560000.serial: Failed preparing Tx DMA descriptor
>
>0xe656000c = HSCIF2 Transmit FIFO data register.

Thank you for sharing.
I was able to reproduce the issue on Gray Hawk Single(r8a779h2).

>With "#define DEBUG" added to drivers/dma/sh/rcar-dmac.c:
>
>    rcar-dmac e7351000.dma-controller: chan1: failed to map 1@0x00000000e656000c
>    sh-sci e6560000.serial: Failed preparing Tx DMA descriptor
>    rcar-dmac e7351000.dma-controller: chan2: map 1@0x00000000e6560014
>to 0x00000000fff82014 dir: DMA_TO_DEVICE
>    rcar-dmac e7351000.dma-controller: chan2: chunk
>00000000e5110c20/000000005e0ede90 sgl 0@000000000d8c5440, 256/256
>0x00000000fff82014 -> 0x00000000ffed6000
>    rcar-dmac e7351000.dma-controller: chan2: submit #2@000000005e0ede90
>    rcar-dmac e7351000.dma-controller: chan2: chunk
>0000000025f2f66c/00000000e5f0dd15 sgl 0@0000000064f1067f, 256/256
>0x00000000fff82014 -> 0x00000000ffed6100
>    rcar-dmac e7351000.dma-controller: chan2: submit #3@00000000e5f0dd15
>    rcar-dmac e7351000.dma-controller: chan2: queue chunk
>00000000e5110c20: 256@0x00000000fff82014 -> 0x00000000ffed6000
>
>0xe6560014 = HSCIF2 Receive FIFO data register

Does IPMMU support handling FIFO registers?
(Forgive me the question... I'm still trying to learn how it works.)

If not, with now dma-controller backed with IPMMU, maybe what
we need is to map FIFO register directly like it used to do?

>Comparing to the CONFIG_IPMMU_VMSA=n case:
>
>    rcar-dmac e7351000.dma-controller: chan1: map 1@0x00000000e656000c
>to 0x00000000e656000c dir: DMA_FROM_DEVICE
>    rcar-dmac e7351000.dma-controller: chan1: chunk
>0000000096396eb4/00000000f35357b6 sgl 0@0000000013546bf6, 74/74
>0x0000000489ab5000 -> 0x00000000e656000c
>    rcar-dmac e7351000.dma-controller: chan1: submit #2@00000000f35357b6
>    rcar-dmac e7351000.dma-controller: chan1: queue chunk
>0000000096396eb4: 74@0x0000000489ab5000 -> 0x00000000e656000c
>
>This confuses me even more: why no DMA_TO_DEVICE mapping in the
>latter case?

I believe the DEVICE being reffered in DMA_FROM_DEVICE is
DMAC rather than FIFO TX register.
So from DMAC's point of view, the dma of DMAC->FIFO TX register
should be think of it as DMA_FROM_DEVICE. 

>>  };
>>
>>  static bool ipmmu_device_is_allowed(struct device *dev)
>
>Gr{oetje,eeting}s,
>
>                        Geert

Sincerely,
Ryo Takakura

Re: [PATCH] iommu: ipmmu-vmsa: Add DMA controllers to devices_allowlist

Posted by Koichiro Den 2 months, 1 week ago

On Mon, Nov 03, 2025 at 05:56:12PM +0900, Ryo Takakura wrote:
> Hi, Geert!
> 
> I'm helping out Den-san a bit on the issue.
> 
> On Wed, 29 Oct 2025 17:08:07 +0100, Geert Uytterhoeven wrote:
> >On Mon, 27 Oct 2025 at 02:26, Koichiro Den <den@valinux.co.jp> wrote:
> >> Add Renesas DMA controller devices to the devices_allowlist to enable
> >> their use with the IPMMU. This allows DMA channels to operate through
> >> the IOMMU when enabled.
> >>
> >> Signed-off-by: Koichiro Den <den@valinux.co.jp>
> >
> >Thanks for your patch!
> >
> >> --- a/drivers/iommu/ipmmu-vmsa.c
> >> +++ b/drivers/iommu/ipmmu-vmsa.c
> >> @@ -741,7 +741,9 @@ static const char * const devices_allowlist[] = {
> >>         "ee100000.mmc",
> >>         "ee120000.mmc",
> >>         "ee140000.mmc",
> >> -       "ee160000.mmc"
> >> +       "ee160000.mmc",
> >> +       "e7350000.dma-controller",
> >> +       "e7351000.dma-controller"
> >
> >While your change looks correct to me, it causes DMA mapping failures on
> >Gray Hawk Single and Sparrow Hawk when IPMMU support is enabled
> >(on renesas-drivers-2025-10-28-v6.18-rc3 with renesas_defconfig
> >+ CONFIG_IPMMU_VMSA=y):
> >
> >    rcar-dmac e7351000.dma-controller: chan1: failed to map 1@0x00000000e656000c
> >    sh-sci e6560000.serial: Failed preparing Tx DMA descriptor
> >
> >0xe656000c = HSCIF2 Transmit FIFO data register.
> 
> Thank you for sharing.
> I was able to reproduce the issue on Gray Hawk Single(r8a779h2).
> 
> >With "#define DEBUG" added to drivers/dma/sh/rcar-dmac.c:
> >
> >    rcar-dmac e7351000.dma-controller: chan1: failed to map 1@0x00000000e656000c
> >    sh-sci e6560000.serial: Failed preparing Tx DMA descriptor
> >    rcar-dmac e7351000.dma-controller: chan2: map 1@0x00000000e6560014
> >to 0x00000000fff82014 dir: DMA_TO_DEVICE
> >    rcar-dmac e7351000.dma-controller: chan2: chunk
> >00000000e5110c20/000000005e0ede90 sgl 0@000000000d8c5440, 256/256
> >0x00000000fff82014 -> 0x00000000ffed6000
> >    rcar-dmac e7351000.dma-controller: chan2: submit #2@000000005e0ede90
> >    rcar-dmac e7351000.dma-controller: chan2: chunk
> >0000000025f2f66c/00000000e5f0dd15 sgl 0@0000000064f1067f, 256/256
> >0x00000000fff82014 -> 0x00000000ffed6100
> >    rcar-dmac e7351000.dma-controller: chan2: submit #3@00000000e5f0dd15
> >    rcar-dmac e7351000.dma-controller: chan2: queue chunk
> >00000000e5110c20: 256@0x00000000fff82014 -> 0x00000000ffed6000
> >
> >0xe6560014 = HSCIF2 Receive FIFO data register
> 
> Does IPMMU support handling FIFO registers?
> (Forgive me the question... I'm still trying to learn how it works.)
> 
> If not, with now dma-controller backed with IPMMU, maybe what
> we need is to map FIFO register directly like it used to do?
> 
> >Comparing to the CONFIG_IPMMU_VMSA=n case:
> >
> >    rcar-dmac e7351000.dma-controller: chan1: map 1@0x00000000e656000c
> >to 0x00000000e656000c dir: DMA_FROM_DEVICE
> >    rcar-dmac e7351000.dma-controller: chan1: chunk
> >0000000096396eb4/00000000f35357b6 sgl 0@0000000013546bf6, 74/74
> >0x0000000489ab5000 -> 0x00000000e656000c
> >    rcar-dmac e7351000.dma-controller: chan1: submit #2@00000000f35357b6
> >    rcar-dmac e7351000.dma-controller: chan1: queue chunk
> >0000000096396eb4: 74@0x0000000489ab5000 -> 0x00000000e656000c
> >
> >This confuses me even more: why no DMA_TO_DEVICE mapping in the
> >latter case?
> 
> I believe the DEVICE being reffered in DMA_FROM_DEVICE is
> DMAC rather than FIFO TX register.
> So from DMAC's point of view, the dma of DMAC->FIFO TX register
> should be think of it as DMA_FROM_DEVICE. 
> 
> >>  };
> >>
> >>  static bool ipmmu_device_is_allowed(struct device *dev)
> >
> >Gr{oetje,eeting}s,
> >
> >                        Geert
> 
> Sincerely,
> Ryo Takakura

Hi Geert and Takakura-san,

My sincere apologies for the very late follow-up email. Unfortunately, I
don't have access to Gray Hawk Single / Sparrow Hawk boards myself, so I
have not been able to reproduce the issue locally. Takakura-san does have
access to them and was able to reproduce the problem, thanks, Takakura-san.

As an update, at least for me, this patch will no longer be necessary due
to another ongoing work, "NTB transport backed by remote DW eDMA":
https://lore.kernel.org/all/20251129160405.2568284-1-den@valinux.co.jp/

Given that, I'm rather inclined to keep this on hold for now, unless you
have any objections.

Thank you both for your time and support.

Koichiro