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[PATCH] New config added to handle 64-bit systems with 32-bit DMA support

Alberto Secondi posted 1 patch 1 year, 7 months ago 
include/linux/dma-mapping.h | 4 ++++
kernel/dma/Kconfig          | 8 ++++++++
2 files changed, 12 insertions(+)
[PATCH] New config added to handle 64-bit systems with 32-bit DMA support
Posted by Alberto Secondi 1 year, 7 months ago 
From: Alberto Secondi <alberto.secondi@abinsula.com>

The kernel assumes that 64-bit systems have 64-bit DMA support through
CONFIG_ARCH_DMA_ADDR_T_64BIT. This is not always true; for example, several
iMX8 systems (verified on iMX8MM and iMX8MP) have DMA with only 32-bit support.
This results in several drivers requesting DMA_BIT_MASK(64), which causes
malfunctions, particularly when systems have more than 3GB of DRAM (verified
with the lan743x driver and iMX8 systems with 4GB of DRAM). Therefore, a new
config ARCH_64BIT_HAS_DMA32_ONLY was added to manage 64-bit systems with 32-bit
DMA, which adjusts DMA_BIT_MASK(n) accordingly.

Signed-off-by: Alberto Secondi <alberto.secondi@abinsula.com>
Co-developed-by: Davide Salaris <davide.salaris@abinsula.com>
---
 include/linux/dma-mapping.h | 4 ++++
 kernel/dma/Kconfig          | 8 ++++++++
 2 files changed, 12 insertions(+)

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index f693aafe221f..629220a777e3 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -74,7 +74,11 @@
  */
 #define DMA_MAPPING_ERROR		(~(dma_addr_t)0)
 
+#ifdef CONFIG_ARCH_64BIT_HAS_DMA32_ONLY
+#define DMA_BIT_MASK(n)	(((n) > 32) ? ((1ULL<<(32))-1) : ((1ULL<<(n))-1))
+#else
 #define DMA_BIT_MASK(n)	(((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
+#endif
 
 #ifdef CONFIG_DMA_API_DEBUG
 void debug_dma_mapping_error(struct device *dev, dma_addr_t dma_addr);
diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
index c06e56be0ca1..0a27eafed808 100644
--- a/kernel/dma/Kconfig
+++ b/kernel/dma/Kconfig
@@ -36,6 +36,14 @@ config NEED_DMA_MAP_STATE
 config ARCH_DMA_ADDR_T_64BIT
 	def_bool 64BIT || PHYS_ADDR_T_64BIT
 
+config ARCH_64BIT_HAS_DMA32_ONLY
+        bool "64bit System has DMA32 only"
+        depends on ARCH_DMA_ADDR_T_64BIT
+        default n
+	help
+	  This enables forcing the maximum DMA_BIT_MASK to 32 bits for
+	  64-bit systems that have DMA support limited to 32 bits.
+
 config ARCH_HAS_DMA_SET_MASK
 	bool
 
-- 
2.34.1
Re: [PATCH] New config added to handle 64-bit systems with 32-bit DMA support
Posted by Robin Murphy 1 year, 7 months ago 
On 2024-06-19 10:17 am, Alberto Secondi wrote:
> ------ Tessian Warning ------
> 
> Be careful, the email's sending address "albertosecondi@gmail[.]com" has never been seen on your company's network before today
> 
> This warning message will be removed if you reply to or forward this email to a recipient outside of your organization.
> 
> ---- Tessian Warning End ----
> 
> From: Alberto Secondi <alberto.secondi@abinsula.com>
> 
> The kernel assumes that 64-bit systems have 64-bit DMA support through
> CONFIG_ARCH_DMA_ADDR_T_64BIT. This is not always true; for example, several
> iMX8 systems (verified on iMX8MM and iMX8MP) have DMA with only 32-bit support.
> This results in several drivers requesting DMA_BIT_MASK(64), which causes
> malfunctions, particularly when systems have more than 3GB of DRAM (verified
> with the lan743x driver and iMX8 systems with 4GB of DRAM). Therefore, a new
> config ARCH_64BIT_HAS_DMA32_ONLY was added to manage 64-bit systems with 32-bit
> DMA, which adjusts DMA_BIT_MASK(n) accordingly.

No. If a system has devices naturally capable of >32-bit DMA, and memory 
at >32-bit system physical addresses, but only a 32-bit interconnect in 
between, that needs to be described properly in Devicetree/ACPI, not 
hacked around with completely non-portable kernel bodges.

Thanks,
Robin.

> Signed-off-by: Alberto Secondi <alberto.secondi@abinsula.com>
> Co-developed-by: Davide Salaris <davide.salaris@abinsula.com>
> ---
>   include/linux/dma-mapping.h | 4 ++++
>   kernel/dma/Kconfig          | 8 ++++++++
>   2 files changed, 12 insertions(+)
> 
> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index f693aafe221f..629220a777e3 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -74,7 +74,11 @@
>    */
>   #define DMA_MAPPING_ERROR		(~(dma_addr_t)0)
>   
> +#ifdef CONFIG_ARCH_64BIT_HAS_DMA32_ONLY
> +#define DMA_BIT_MASK(n)	(((n) > 32) ? ((1ULL<<(32))-1) : ((1ULL<<(n))-1))
> +#else
>   #define DMA_BIT_MASK(n)	(((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
> +#endif
>   
>   #ifdef CONFIG_DMA_API_DEBUG
>   void debug_dma_mapping_error(struct device *dev, dma_addr_t dma_addr);
> diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
> index c06e56be0ca1..0a27eafed808 100644
> --- a/kernel/dma/Kconfig
> +++ b/kernel/dma/Kconfig
> @@ -36,6 +36,14 @@ config NEED_DMA_MAP_STATE
>   config ARCH_DMA_ADDR_T_64BIT
>   	def_bool 64BIT || PHYS_ADDR_T_64BIT
>   
> +config ARCH_64BIT_HAS_DMA32_ONLY
> +        bool "64bit System has DMA32 only"
> +        depends on ARCH_DMA_ADDR_T_64BIT
> +        default n
> +	help
> +	  This enables forcing the maximum DMA_BIT_MASK to 32 bits for
> +	  64-bit systems that have DMA support limited to 32 bits.
> +
>   config ARCH_HAS_DMA_SET_MASK
>   	bool
>
Re: [PATCH] New config added to handle 64-bit systems with 32-bit DMA support
Posted by Michael Nazzareno Trimarchi 1 year, 7 months ago 
Hi Robin

On Wed, Jun 19, 2024 at 12:36 PM Robin Murphy <robin.murphy@arm.com> wrote:
>
> On 2024-06-19 10:17 am, Alberto Secondi wrote:
> > ------ Tessian Warning ------
> >
> > Be careful, the email's sending address "albertosecondi@gmail[.]com" has never been seen on your company's network before today
> >
> > This warning message will be removed if you reply to or forward this email to a recipient outside of your organization.
> >
> > ---- Tessian Warning End ----
> >
> > From: Alberto Secondi <alberto.secondi@abinsula.com>
> >
> > The kernel assumes that 64-bit systems have 64-bit DMA support through
> > CONFIG_ARCH_DMA_ADDR_T_64BIT. This is not always true; for example, several
> > iMX8 systems (verified on iMX8MM and iMX8MP) have DMA with only 32-bit support.
> > This results in several drivers requesting DMA_BIT_MASK(64), which causes
> > malfunctions, particularly when systems have more than 3GB of DRAM (verified
> > with the lan743x driver and iMX8 systems with 4GB of DRAM). Therefore, a new
> > config ARCH_64BIT_HAS_DMA32_ONLY was added to manage 64-bit systems with 32-bit
> > DMA, which adjusts DMA_BIT_MASK(n) accordingly.
>
> No. If a system has devices naturally capable of >32-bit DMA, and memory
> at >32-bit system physical addresses, but only a 32-bit interconnect in
> between, that needs to be described properly in Devicetree/ACPI, not
> hacked around with completely non-portable kernel bodges.
>

commit 4251a3ac4de9625a284a9c046cc915487e9b2a5e
Author: Lucas Stach <l.stach@pengutronix.de>
Date:   Tue May 4 10:20:51 2021 +0200

    arm64: dts: imx8mm: specify dma-ranges

    DMA addressing capabilities on i.MX8MM are limited by the interconnect,
    same as on i.MX8MQ. Add dma-ranges to the the peripheral bus to let
    the kernel know about this.

    Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
    Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
    Tested-by: Frieder Schrempf <frieder.schrempf@kontron.de>
    Signed-off-by: Shawn Guo <shawnguo@kernel.org>

diff --git a/arch/arm64/boot/dts/freescale/imx8mm.dtsi
b/arch/arm64/boot/dts/freescale/imx8mm.dtsi
index 64aa38fd2b6e0..e7648c3b83905 100644
--- a/arch/arm64/boot/dts/freescale/imx8mm.dtsi
+++ b/arch/arm64/boot/dts/freescale/imx8mm.dtsi
@@ -261,6 +261,7 @@ soc@0 {
                #address-cells = <1>;
                #size-cells = <1>;
                ranges = <0x0 0x0 0x0 0x3e000000>;
+               dma-ranges = <0x40000000 0x0 0x40000000 0xc0000000>;
                nvmem-cells = <&imx8mm_uid>;
                nvmem-cell-names = "soc_unique_id";


Somenthing like this should already do it?

Michael

> Thanks,
> Robin.
>
> > Signed-off-by: Alberto Secondi <alberto.secondi@abinsula.com>
> > Co-developed-by: Davide Salaris <davide.salaris@abinsula.com>
> > ---
> >   include/linux/dma-mapping.h | 4 ++++
> >   kernel/dma/Kconfig          | 8 ++++++++
> >   2 files changed, 12 insertions(+)
> >
> > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> > index f693aafe221f..629220a777e3 100644
> > --- a/include/linux/dma-mapping.h
> > +++ b/include/linux/dma-mapping.h
> > @@ -74,7 +74,11 @@
> >    */
> >   #define DMA_MAPPING_ERROR           (~(dma_addr_t)0)
> >
> > +#ifdef CONFIG_ARCH_64BIT_HAS_DMA32_ONLY
> > +#define DMA_BIT_MASK(n)      (((n) > 32) ? ((1ULL<<(32))-1) : ((1ULL<<(n))-1))
> > +#else
> >   #define DMA_BIT_MASK(n)     (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
> > +#endif
> >
> >   #ifdef CONFIG_DMA_API_DEBUG
> >   void debug_dma_mapping_error(struct device *dev, dma_addr_t dma_addr);
> > diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
> > index c06e56be0ca1..0a27eafed808 100644
> > --- a/kernel/dma/Kconfig
> > +++ b/kernel/dma/Kconfig
> > @@ -36,6 +36,14 @@ config NEED_DMA_MAP_STATE
> >   config ARCH_DMA_ADDR_T_64BIT
> >       def_bool 64BIT || PHYS_ADDR_T_64BIT
> >
> > +config ARCH_64BIT_HAS_DMA32_ONLY
> > +        bool "64bit System has DMA32 only"
> > +        depends on ARCH_DMA_ADDR_T_64BIT
> > +        default n
> > +     help
> > +       This enables forcing the maximum DMA_BIT_MASK to 32 bits for
> > +       64-bit systems that have DMA support limited to 32 bits.
> > +
> >   config ARCH_HAS_DMA_SET_MASK
> >       bool
> >
>
Re: [PATCH] New config added to handle 64-bit systems with 32-bit DMA support
Posted by Robin Murphy 1 year, 7 months ago 
On 2024-06-19 12:43 pm, Michael Nazzareno Trimarchi wrote:
> Hi Robin
> 
> On Wed, Jun 19, 2024 at 12:36 PM Robin Murphy <robin.murphy@arm.com> wrote:
>>
>> On 2024-06-19 10:17 am, Alberto Secondi wrote:
>>> ------ Tessian Warning ------
>>>
>>> Be careful, the email's sending address "albertosecondi@gmail[.]com" has never been seen on your company's network before today
>>>
>>> This warning message will be removed if you reply to or forward this email to a recipient outside of your organization.
>>>
>>> ---- Tessian Warning End ----
>>>
>>> From: Alberto Secondi <alberto.secondi@abinsula.com>
>>>
>>> The kernel assumes that 64-bit systems have 64-bit DMA support through
>>> CONFIG_ARCH_DMA_ADDR_T_64BIT. This is not always true; for example, several
>>> iMX8 systems (verified on iMX8MM and iMX8MP) have DMA with only 32-bit support.
>>> This results in several drivers requesting DMA_BIT_MASK(64), which causes
>>> malfunctions, particularly when systems have more than 3GB of DRAM (verified
>>> with the lan743x driver and iMX8 systems with 4GB of DRAM). Therefore, a new
>>> config ARCH_64BIT_HAS_DMA32_ONLY was added to manage 64-bit systems with 32-bit
>>> DMA, which adjusts DMA_BIT_MASK(n) accordingly.
>>
>> No. If a system has devices naturally capable of >32-bit DMA, and memory
>> at >32-bit system physical addresses, but only a 32-bit interconnect in
>> between, that needs to be described properly in Devicetree/ACPI, not
>> hacked around with completely non-portable kernel bodges.
>>
> 
> commit 4251a3ac4de9625a284a9c046cc915487e9b2a5e
> Author: Lucas Stach <l.stach@pengutronix.de>
> Date:   Tue May 4 10:20:51 2021 +0200
> 
>      arm64: dts: imx8mm: specify dma-ranges
> 
>      DMA addressing capabilities on i.MX8MM are limited by the interconnect,
>      same as on i.MX8MQ. Add dma-ranges to the the peripheral bus to let
>      the kernel know about this.
> 
>      Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
>      Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
>      Tested-by: Frieder Schrempf <frieder.schrempf@kontron.de>
>      Signed-off-by: Shawn Guo <shawnguo@kernel.org>
> 
> diff --git a/arch/arm64/boot/dts/freescale/imx8mm.dtsi
> b/arch/arm64/boot/dts/freescale/imx8mm.dtsi
> index 64aa38fd2b6e0..e7648c3b83905 100644
> --- a/arch/arm64/boot/dts/freescale/imx8mm.dtsi
> +++ b/arch/arm64/boot/dts/freescale/imx8mm.dtsi
> @@ -261,6 +261,7 @@ soc@0 {
>                  #address-cells = <1>;
>                  #size-cells = <1>;
>                  ranges = <0x0 0x0 0x0 0x3e000000>;
> +               dma-ranges = <0x40000000 0x0 0x40000000 0xc0000000>;
>                  nvmem-cells = <&imx8mm_uid>;
>                  nvmem-cell-names = "soc_unique_id";
> 
> 
> Somenthing like this should already do it?

Hmm, indeed... so the question to dig into would be why that's 
apparently not getting picked up by of_dma_get_range() for that device.

Thanks,
Robin.
Re: [PATCH] New config added to handle 64-bit systems with 32-bit DMA support
Posted by Michael Nazzareno Trimarchi 1 year, 7 months ago 
Hi Robin

On Wed, Jun 19, 2024 at 2:46 PM Robin Murphy <robin.murphy@arm.com> wrote:
>
>
> On 2024-06-19 12:43 pm, Michael Nazzareno Trimarchi wrote:
> > Hi Robin
> >
> > On Wed, Jun 19, 2024 at 12:36 PM Robin Murphy <robin.murphy@arm.com> wrote:
> >>
> >> On 2024-06-19 10:17 am, Alberto Secondi wrote:
> >>> ------ Tessian Warning ------
> >>>
> >>> Be careful, the email's sending address "albertosecondi@gmail[.]com" has never been seen on your company's network before today
> >>>
> >>> This warning message will be removed if you reply to or forward this email to a recipient outside of your organization.
> >>>
> >>> ---- Tessian Warning End ----
> >>>
> >>> From: Alberto Secondi <alberto.secondi@abinsula.com>
> >>>
> >>> The kernel assumes that 64-bit systems have 64-bit DMA support through
> >>> CONFIG_ARCH_DMA_ADDR_T_64BIT. This is not always true; for example, several
> >>> iMX8 systems (verified on iMX8MM and iMX8MP) have DMA with only 32-bit support.
> >>> This results in several drivers requesting DMA_BIT_MASK(64), which causes
> >>> malfunctions, particularly when systems have more than 3GB of DRAM (verified
> >>> with the lan743x driver and iMX8 systems with 4GB of DRAM). Therefore, a new
> >>> config ARCH_64BIT_HAS_DMA32_ONLY was added to manage 64-bit systems with 32-bit
> >>> DMA, which adjusts DMA_BIT_MASK(n) accordingly.
> >>
> >> No. If a system has devices naturally capable of >32-bit DMA, and memory
> >> at >32-bit system physical addresses, but only a 32-bit interconnect in
> >> between, that needs to be described properly in Devicetree/ACPI, not
> >> hacked around with completely non-portable kernel bodges.
> >>
> >
> > commit 4251a3ac4de9625a284a9c046cc915487e9b2a5e
> > Author: Lucas Stach <l.stach@pengutronix.de>
> > Date:   Tue May 4 10:20:51 2021 +0200
> >
> >      arm64: dts: imx8mm: specify dma-ranges
> >
> >      DMA addressing capabilities on i.MX8MM are limited by the interconnect,
> >      same as on i.MX8MQ. Add dma-ranges to the the peripheral bus to let
> >      the kernel know about this.
> >
> >      Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
> >      Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
> >      Tested-by: Frieder Schrempf <frieder.schrempf@kontron.de>
> >      Signed-off-by: Shawn Guo <shawnguo@kernel.org>
> >
> > diff --git a/arch/arm64/boot/dts/freescale/imx8mm.dtsi
> > b/arch/arm64/boot/dts/freescale/imx8mm.dtsi
> > index 64aa38fd2b6e0..e7648c3b83905 100644
> > --- a/arch/arm64/boot/dts/freescale/imx8mm.dtsi
> > +++ b/arch/arm64/boot/dts/freescale/imx8mm.dtsi
> > @@ -261,6 +261,7 @@ soc@0 {
> >                  #address-cells = <1>;
> >                  #size-cells = <1>;
> >                  ranges = <0x0 0x0 0x0 0x3e000000>;
> > +               dma-ranges = <0x40000000 0x0 0x40000000 0xc0000000>;
> >                  nvmem-cells = <&imx8mm_uid>;
> >                  nvmem-cell-names = "soc_unique_id";
> >
> >
> > Somenthing like this should already do it?
>
> Hmm, indeed... so the question to dig into would be why that's
> apparently not getting picked up by of_dma_get_range() for that device.
>

The patch does not include what kernel version was tested.  After we
have this answer that
we can know

Michael

> Thanks,
> Robin.



-- 
Michael Nazzareno Trimarchi
Co-Founder & Chief Executive Officer
M. +39 347 913 2170
michael@amarulasolutions.com
__________________________________

Amarula Solutions BV
Joop Geesinkweg 125, 1114 AB, Amsterdam, NL
T. +31 (0)85 111 9172
info@amarulasolutions.com
www.amarulasolutions.com
Re: [PATCH] New config added to handle 64-bit systems with 32-bit DMA support
Posted by Michael Nazzareno Trimarchi 1 year, 7 months ago 
Hi Alberto

On Wed, Jun 19, 2024 at 11:20 AM Alberto Secondi
<albertosecondi@gmail.com> wrote:
>
> From: Alberto Secondi <alberto.secondi@abinsula.com>
>
> The kernel assumes that 64-bit systems have 64-bit DMA support through
> CONFIG_ARCH_DMA_ADDR_T_64BIT. This is not always true; for example, several
> iMX8 systems (verified on iMX8MM and iMX8MP) have DMA with only 32-bit support.
> This results in several drivers requesting DMA_BIT_MASK(64), which causes
> malfunctions, particularly when systems have more than 3GB of DRAM (verified
> with the lan743x driver and iMX8 systems with 4GB of DRAM). Therefore, a new
> config ARCH_64BIT_HAS_DMA32_ONLY was added to manage 64-bit systems with 32-bit
> DMA, which adjusts DMA_BIT_MASK(n) accordingly.
>
> Signed-off-by: Alberto Secondi <alberto.secondi@abinsula.com>
> Co-developed-by: Davide Salaris <davide.salaris@abinsula.com>
> ---
>  include/linux/dma-mapping.h | 4 ++++
>  kernel/dma/Kconfig          | 8 ++++++++
>  2 files changed, 12 insertions(+)
>
> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index f693aafe221f..629220a777e3 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -74,7 +74,11 @@
>   */
>  #define DMA_MAPPING_ERROR              (~(dma_addr_t)0)
>
> +#ifdef CONFIG_ARCH_64BIT_HAS_DMA32_ONLY
> +#define DMA_BIT_MASK(n)        (((n) > 32) ? ((1ULL<<(32))-1) : ((1ULL<<(n))-1))
> +#else
>  #define DMA_BIT_MASK(n)        (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
> +#endif
>

How can this fit configuration where you want to have one Kernel image
for several arm64 machine?

Michael

>  #ifdef CONFIG_DMA_API_DEBUG
>  void debug_dma_mapping_error(struct device *dev, dma_addr_t dma_addr);
> diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
> index c06e56be0ca1..0a27eafed808 100644
> --- a/kernel/dma/Kconfig
> +++ b/kernel/dma/Kconfig
> @@ -36,6 +36,14 @@ config NEED_DMA_MAP_STATE
>  config ARCH_DMA_ADDR_T_64BIT
>         def_bool 64BIT || PHYS_ADDR_T_64BIT
>
> +config ARCH_64BIT_HAS_DMA32_ONLY
> +        bool "64bit System has DMA32 only"
> +        depends on ARCH_DMA_ADDR_T_64BIT
> +        default n
> +       help
> +         This enables forcing the maximum DMA_BIT_MASK to 32 bits for
> +         64-bit systems that have DMA support limited to 32 bits.
> +
>  config ARCH_HAS_DMA_SET_MASK
>         bool
>
> --
> 2.34.1
>
>
Re: [PATCH] New config added to handle 64-bit systems with 32-bit DMA support
Posted by Michael Nazzareno Trimarchi 1 year, 7 months ago 
Hi Alberto

On Wed, Jun 19, 2024 at 11:23 AM Michael Nazzareno Trimarchi
<michael@amarulasolutions.com> wrote:
>
> Hi Alberto
>
> On Wed, Jun 19, 2024 at 11:20 AM Alberto Secondi
> <albertosecondi@gmail.com> wrote:
> >
> > From: Alberto Secondi <alberto.secondi@abinsula.com>
> >
> > The kernel assumes that 64-bit systems have 64-bit DMA support through
> > CONFIG_ARCH_DMA_ADDR_T_64BIT. This is not always true; for example, several
> > iMX8 systems (verified on iMX8MM and iMX8MP) have DMA with only 32-bit support.
> > This results in several drivers requesting DMA_BIT_MASK(64), which causes
> > malfunctions, particularly when systems have more than 3GB of DRAM (verified
> > with the lan743x driver and iMX8 systems with 4GB of DRAM). Therefore, a new
> > config ARCH_64BIT_HAS_DMA32_ONLY was added to manage 64-bit systems with 32-bit
> > DMA, which adjusts DMA_BIT_MASK(n) accordingly.
> >
> > Signed-off-by: Alberto Secondi <alberto.secondi@abinsula.com>
> > Co-developed-by: Davide Salaris <davide.salaris@abinsula.com>
> > ---
> >  include/linux/dma-mapping.h | 4 ++++
> >  kernel/dma/Kconfig          | 8 ++++++++
> >  2 files changed, 12 insertions(+)
> >
> > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> > index f693aafe221f..629220a777e3 100644
> > --- a/include/linux/dma-mapping.h
> > +++ b/include/linux/dma-mapping.h
> > @@ -74,7 +74,11 @@
> >   */
> >  #define DMA_MAPPING_ERROR              (~(dma_addr_t)0)
> >
> > +#ifdef CONFIG_ARCH_64BIT_HAS_DMA32_ONLY
> > +#define DMA_BIT_MASK(n)        (((n) > 32) ? ((1ULL<<(32))-1) : ((1ULL<<(n))-1))
> > +#else
> >  #define DMA_BIT_MASK(n)        (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
> > +#endif
> >
>
> How can this fit configuration where you want to have one Kernel image
> for several arm64 machine?
>

I'm not an expert here but:

 @coherent_dma_mask: Like dma_mask, but for alloc_coherent mapping as not all
 *         hardware supports 64-bit addresses for consistent allocations
 *         such descriptors.

This looks more connected to what you are looking for.

Michael


> Michael
>
> >  #ifdef CONFIG_DMA_API_DEBUG
> >  void debug_dma_mapping_error(struct device *dev, dma_addr_t dma_addr);
> > diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
> > index c06e56be0ca1..0a27eafed808 100644
> > --- a/kernel/dma/Kconfig
> > +++ b/kernel/dma/Kconfig
> > @@ -36,6 +36,14 @@ config NEED_DMA_MAP_STATE
> >  config ARCH_DMA_ADDR_T_64BIT
> >         def_bool 64BIT || PHYS_ADDR_T_64BIT
> >
> > +config ARCH_64BIT_HAS_DMA32_ONLY
> > +        bool "64bit System has DMA32 only"
> > +        depends on ARCH_DMA_ADDR_T_64BIT
> > +        default n
> > +       help
> > +         This enables forcing the maximum DMA_BIT_MASK to 32 bits for
> > +         64-bit systems that have DMA support limited to 32 bits.
> > +
> >  config ARCH_HAS_DMA_SET_MASK
> >         bool
> >
> > --
> > 2.34.1
> >
> >

Patchew 2.1-devel-b67e4c2

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