| Message ID | 20230803111455.811339-1-devarsht@ti.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: dts: ti: k3-am62x-sk-common: Reserve 128MiB of global CMA | expand |
On 16:44-20230803, Devarsh Thakkar wrote: > Reserve 128MiB of global CMA which is also marked as re-usable > so that OS can also use the same if peripheral drivers are not using the > same. > > AM62x supports multimedia components such as GPU, dual Display and Camera. > Assuming the worst-case scenario where all 3 are run in parallel below > is the calculation : > > 1) OV5640 camera sensor supports 1920x1080 resolution > -> 1920 width x 1080 height x 2 bytesperpixel x 8 buffers > (default in yavta) : 32MiB > > 2) 1920x1200 Microtips LVDS panel supported > -> 1920 width x 1080 height x 4 bytesperpixel x 2 buffers : > 16 MiB > > 3) 1920x1080 HDMI display supported > -> 1920 width x 1080 height x 4 bytesperpixel x 2 buffers : > 15.82 MiB which is ~16 MiB > > 4) IMG GPU shares with display allocated buffers while rendering > but in case some dedicated operation viz color conversion, > keeping same window of ~16 MiB for GPU too. > > Total is 80 MiB and adding 32 MiB for other peripherals and extra > 16 MiB to keep as buffer for fragmentation thus rounding total to 128 > MiB. > > Signed-off-by: Devarsh Thakkar <devarsht@ti.com> > Acked-by: Darren Etheridge <detheridge@ti.com> > Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com> > --- I don't think this is right approach. There are other techniques than having to do this (Andrew: please comment) and require drivers to behave properly. I am esp concerned since there are platforms based on am62x and just 256MB DDR. > arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi b/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi > index 34c8ffc553ec..9dd6e23ca9ca 100644 > --- a/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi > +++ b/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi > @@ -47,6 +47,14 @@ ramoops@9ca00000 { > pmsg-size = <0x8000>; > }; > > + /* global cma region */ > + linux,cma { > + compatible = "shared-dma-pool"; > + reusable; > + size = <0x00 0x8000000>; > + linux,cma-default; > + }; > + > secure_tfa_ddr: tfa@9e780000 { > reg = <0x00 0x9e780000 0x00 0x80000>; > alignment = <0x1000>; > -- > 2.34.1 >
Hi Nishanth, Thanks for the review. On 06/08/23 01:03, Nishanth Menon wrote: > On 16:44-20230803, Devarsh Thakkar wrote: >> Reserve 128MiB of global CMA which is also marked as re-usable >> so that OS can also use the same if peripheral drivers are not using the >> same. >> >> AM62x supports multimedia components such as GPU, dual Display and Camera. >> Assuming the worst-case scenario where all 3 are run in parallel below >> is the calculation : >> >> 1) OV5640 camera sensor supports 1920x1080 resolution >> -> 1920 width x 1080 height x 2 bytesperpixel x 8 buffers >> (default in yavta) : 32MiB >> >> 2) 1920x1200 Microtips LVDS panel supported >> -> 1920 width x 1080 height x 4 bytesperpixel x 2 buffers : >> 16 MiB >> >> 3) 1920x1080 HDMI display supported >> -> 1920 width x 1080 height x 4 bytesperpixel x 2 buffers : >> 15.82 MiB which is ~16 MiB >> >> 4) IMG GPU shares with display allocated buffers while rendering >> but in case some dedicated operation viz color conversion, >> keeping same window of ~16 MiB for GPU too. >> >> Total is 80 MiB and adding 32 MiB for other peripherals and extra >> 16 MiB to keep as buffer for fragmentation thus rounding total to 128 >> MiB. >> >> Signed-off-by: Devarsh Thakkar <devarsht@ti.com> >> Acked-by: Darren Etheridge <detheridge@ti.com> >> Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com> >> --- > > I don't think this is right approach. There are other techniques > than having to do this (Andrew: please comment) and require drivers to > behave properly. Sorry but I did not understand clearly the disadvantage of this approach. Here we are reserving CMA and also marking it as re-usable so that in case driver is not using it OS can use that region. Also I see quite a few vendors already taking this approach : $grep -r cma-default arch/arm64/boot/dts arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts:276: linux,cma-default; arch/arm64/boot/dts/qcom/sc8280xp-crd.dts:222: linux,cma-default; arch/arm64/boot/dts/freescale/imx8mp-tqma8mpql-mba8mpxl.dts:201: linux,cma-default; arch/arm64/boot/dts/freescale/imx8ulp-evk.dts:32: linux,cma-default; arch/arm64/boot/dts/freescale/imx8-apalis-v1.1.dtsi:198: linux,cma-default; arch/arm64/boot/dts/freescale/imx8mm-tqma8mqml.dtsi:48: linux,cma-default; arch/arm64/boot/dts/freescale/imx8dxl-evk.dts:50: linux,cma-default; arch/arm64/boot/dts/freescale/imx93-tqma9352.dtsi:24: linux,cma-default; arch/arm64/boot/dts/freescale/imx8mq-tqma8mq.dtsi:59: linux,cma-default; arch/arm64/boot/dts/freescale/imx8mn-tqma8mqnl.dtsi:46: linux,cma-default; arch/arm64/boot/dts/freescale/imx93-11x11-evk.dts:28: linux,cma-default; arch/arm64/boot/dts/hisilicon/hi6220-hikey.dts:67: linux,cma-default; arch/arm64/boot/dts/amlogic/meson-gx.dtsi:63: linux,cma-default; arch/arm64/boot/dts/amlogic/meson-g12-common.dtsi:121: linux,cma-default; arch/arm64/boot/dts/amlogic/meson-a1.dtsi:59: linux,cma-default; I am esp concerned since there are platforms based on > am62x and just 256MB DDR. > The file "k3-am62x-sk-common.dtsi" refers DDR memory size as 2Gb[1] and so I put CMA reservation in same file assuming all boards including this file have 2Gb. But if there are some boards having lesser DDR and including this k3-am62x-sk-common.dtsi and overriding memory node, I can put the CMA reservation node in board specific file i.e. k3-am625-sk.dts in V2. Kindly let me know if above is preferred approach. [1] https://gitlab.com/linux-kernel/linux-next/-/blob/next-20230807/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi?ref_type=tags#L33 Regards Devarsh >> arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi | 8 ++++++++ >> 1 file changed, 8 insertions(+) >> >> diff --git a/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi b/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi >> index 34c8ffc553ec..9dd6e23ca9ca 100644 >> --- a/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi >> +++ b/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi >> @@ -47,6 +47,14 @@ ramoops@9ca00000 { >> pmsg-size = <0x8000>; >> }; >> >> + /* global cma region */ >> + linux,cma { >> + compatible = "shared-dma-pool"; >> + reusable; >> + size = <0x00 0x8000000>; >> + linux,cma-default; >> + }; >> + >> secure_tfa_ddr: tfa@9e780000 { >> reg = <0x00 0x9e780000 0x00 0x80000>; >> alignment = <0x1000>; >> -- >> 2.34.1 >> >
On Sat, Aug 05, 2023 at 02:33:55PM -0500, Nishanth Menon wrote: > I am esp concerned since there are platforms based on am62x and just > 256MB DDR. On that regard, currently you have reserved memory areas just before 512MB DDR limit. Any plan to move those? Francesco
On 08:46-20230807, Francesco Dolcini wrote: > On Sat, Aug 05, 2023 at 02:33:55PM -0500, Nishanth Menon wrote: > > I am esp concerned since there are platforms based on am62x and just > > 256MB DDR. > > On that regard, currently you have reserved memory areas just before > 512MB DDR limit. Any plan to move those? Nope. Common min configuration we have seen is 512MB (why TI evms use that definition). There are exceptional cases of 256MB boards, but in such cases, the board dts should describe it.
On 8/7/23 1:03 AM, Devarsh Thakkar wrote: > Hi Nishanth, > > Thanks for the review. > > On 06/08/23 01:03, Nishanth Menon wrote: >> On 16:44-20230803, Devarsh Thakkar wrote: >>> Reserve 128MiB of global CMA which is also marked as re-usable >>> so that OS can also use the same if peripheral drivers are not using the >>> same. >>> >>> AM62x supports multimedia components such as GPU, dual Display and Camera. >>> Assuming the worst-case scenario where all 3 are run in parallel below >>> is the calculation : >>> >>> 1) OV5640 camera sensor supports 1920x1080 resolution >>> -> 1920 width x 1080 height x 2 bytesperpixel x 8 buffers >>> (default in yavta) : 32MiB >>> >>> 2) 1920x1200 Microtips LVDS panel supported >>> -> 1920 width x 1080 height x 4 bytesperpixel x 2 buffers : >>> 16 MiB >>> >>> 3) 1920x1080 HDMI display supported >>> -> 1920 width x 1080 height x 4 bytesperpixel x 2 buffers : >>> 15.82 MiB which is ~16 MiB >>> >>> 4) IMG GPU shares with display allocated buffers while rendering >>> but in case some dedicated operation viz color conversion, >>> keeping same window of ~16 MiB for GPU too. >>> >>> Total is 80 MiB and adding 32 MiB for other peripherals and extra >>> 16 MiB to keep as buffer for fragmentation thus rounding total to 128 >>> MiB. >>> >>> Signed-off-by: Devarsh Thakkar <devarsht@ti.com> >>> Acked-by: Darren Etheridge <detheridge@ti.com> >>> Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com> >>> --- >> >> I don't think this is right approach. There are other techniques >> than having to do this (Andrew: please comment) and require drivers to >> behave properly. > > Sorry but I did not understand clearly the disadvantage of this approach. > Here we are reserving CMA and also marking it as re-usable so that in case > driver is not using it OS can use that region. > It isn't always that easy, many types of allocations can be pinned and cannot be placed in this region. It still has cost. > Also I see quite a few vendors already taking this approach : > Just because others have gotten away with it doesn't mean it is correct :) There are some cases when the DMA/CMA region needs to be in a specific location as the hardware only supports some addresses (only some address pins wired out, etc..). But general CMA size selection is a configuration and so has no place in DT which should only be used to describe hardware. Another issue I have is that this forces all users of these boards to have this rather large carveout, even if they do not intend to use all of these IP at the same time, or even at all. Actually, upstream we don't support GPU yet, so you can't use all of this carveout anyway. Lastly, large CMA carveouts as in this case are masking a bigger issue, there is hardware IP that cannot handle scatter-gather and there is no system level IOMMU to help with that. This simply does not scale, fragmentation can set in even with CMA in a running system, physically contiguous allocations can still fail. As our devices grow in complexity while still not having an IOMMU we would need to reserve ever increasingly sized CMA areas. This might sound like an ad absurdum argument, but we only need to look at our current evil vendor tree to see where this leads [0]. Yes you are reading the size right, 1.75GB(!) of CMA.. We need a better solution upstream, I'm not claiming I know what that solution is (probably something involved in the memory allocation to allow for more/larger movable pages). But for the above 3 reasons this patch is not a viable solution. [0] https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/tree/arch/arm64/boot/dts/ti/k3-am69-sk.dts?h=ti-linux-6.1.y#n48 Andrew > $grep -r cma-default arch/arm64/boot/dts > arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts:276: > linux,cma-default; > arch/arm64/boot/dts/qcom/sc8280xp-crd.dts:222: > linux,cma-default; > arch/arm64/boot/dts/freescale/imx8mp-tqma8mpql-mba8mpxl.dts:201: > linux,cma-default; > arch/arm64/boot/dts/freescale/imx8ulp-evk.dts:32: > linux,cma-default; > arch/arm64/boot/dts/freescale/imx8-apalis-v1.1.dtsi:198: > linux,cma-default; > arch/arm64/boot/dts/freescale/imx8mm-tqma8mqml.dtsi:48: > linux,cma-default; > arch/arm64/boot/dts/freescale/imx8dxl-evk.dts:50: > linux,cma-default; > arch/arm64/boot/dts/freescale/imx93-tqma9352.dtsi:24: > linux,cma-default; > arch/arm64/boot/dts/freescale/imx8mq-tqma8mq.dtsi:59: > linux,cma-default; > arch/arm64/boot/dts/freescale/imx8mn-tqma8mqnl.dtsi:46: > linux,cma-default; > arch/arm64/boot/dts/freescale/imx93-11x11-evk.dts:28: > linux,cma-default; > arch/arm64/boot/dts/hisilicon/hi6220-hikey.dts:67: > linux,cma-default; > arch/arm64/boot/dts/amlogic/meson-gx.dtsi:63: > linux,cma-default; > arch/arm64/boot/dts/amlogic/meson-g12-common.dtsi:121: > linux,cma-default; > arch/arm64/boot/dts/amlogic/meson-a1.dtsi:59: > linux,cma-default; > > > I am esp concerned since there are platforms based on >> am62x and just 256MB DDR. >> > > The file "k3-am62x-sk-common.dtsi" refers DDR memory size as 2Gb[1] and so I > put CMA reservation in same file assuming all boards including this file have > 2Gb. > > But if there are some boards having lesser DDR and including this > k3-am62x-sk-common.dtsi and overriding memory node, I can put the CMA > reservation node in board specific file i.e. k3-am625-sk.dts in V2. > > Kindly let me know if above is preferred approach. > > [1] > https://gitlab.com/linux-kernel/linux-next/-/blob/next-20230807/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi?ref_type=tags#L33 > > Regards > Devarsh > >>> arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi | 8 ++++++++ >>> 1 file changed, 8 insertions(+) >>> >>> diff --git a/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi b/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi >>> index 34c8ffc553ec..9dd6e23ca9ca 100644 >>> --- a/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi >>> +++ b/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi >>> @@ -47,6 +47,14 @@ ramoops@9ca00000 { >>> pmsg-size = <0x8000>; >>> }; >>> >>> + /* global cma region */ >>> + linux,cma { >>> + compatible = "shared-dma-pool"; >>> + reusable; >>> + size = <0x00 0x8000000>; >>> + linux,cma-default; >>> + }; >>> + >>> secure_tfa_ddr: tfa@9e780000 { >>> reg = <0x00 0x9e780000 0x00 0x80000>; >>> alignment = <0x1000>; >>> -- >>> 2.34.1 >>> >>
Hi Andrew, Thanks for the review. On 07/08/23 23:30, Andrew Davis wrote: > On 8/7/23 1:03 AM, Devarsh Thakkar wrote: >> Hi Nishanth, >> >> Thanks for the review. >> >> On 06/08/23 01:03, Nishanth Menon wrote: >>> On 16:44-20230803, Devarsh Thakkar wrote: >>>> Reserve 128MiB of global CMA which is also marked as re-usable >>>> so that OS can also use the same if peripheral drivers are not using the >>>> same. >>>> >>>> AM62x supports multimedia components such as GPU, dual Display and Camera. >>>> Assuming the worst-case scenario where all 3 are run in parallel below >>>> is the calculation : >>>> >>>> 1) OV5640 camera sensor supports 1920x1080 resolution >>>> -> 1920 width x 1080 height x 2 bytesperpixel x 8 buffers >>>> (default in yavta) : 32MiB >>>> >>>> 2) 1920x1200 Microtips LVDS panel supported >>>> -> 1920 width x 1080 height x 4 bytesperpixel x 2 buffers : >>>> 16 MiB >>>> >>>> 3) 1920x1080 HDMI display supported >>>> -> 1920 width x 1080 height x 4 bytesperpixel x 2 buffers : >>>> 15.82 MiB which is ~16 MiB >>>> >>>> 4) IMG GPU shares with display allocated buffers while rendering >>>> but in case some dedicated operation viz color conversion, >>>> keeping same window of ~16 MiB for GPU too. >>>> >>>> Total is 80 MiB and adding 32 MiB for other peripherals and extra >>>> 16 MiB to keep as buffer for fragmentation thus rounding total to 128 >>>> MiB. >>>> >>>> Signed-off-by: Devarsh Thakkar <devarsht@ti.com> >>>> Acked-by: Darren Etheridge <detheridge@ti.com> >>>> Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com> >>>> --- >>> >>> I don't think this is right approach. There are other techniques >>> than having to do this (Andrew: please comment) and require drivers to >>> behave properly. >> >> Sorry but I did not understand clearly the disadvantage of this approach. >> Here we are reserving CMA and also marking it as re-usable so that in case >> driver is not using it OS can use that region. >> > Agreed, the examples where shared just for informational purpose. > It isn't always that easy, many types of allocations can be pinned and > cannot be placed in this region. It still has cost. > I agree if some allocations are requested with non-moveable pages than cma region can't serve those, but that looks more like a tradeoff to me as we also want to support those drivers requiring CMA to use it on-demand and for allocations requiring non-moveable pages they can be still served through non-CMA region. >> Also I see quite a few vendors already taking this approach : >> > > Just because others have gotten away with it doesn't mean it is correct :) > > There are some cases when the DMA/CMA region needs to be in a specific > location as the hardware only supports some addresses (only some address > pins wired out, etc..). But general CMA size selection is a configuration > and so has no place in DT which should only be used to describe hardware. > But I do see the DT specification [0] mentioning this provision for CMA size selection, so I don't think we are violating the DT specification while choosing to set CMA size this way : > Another issue I have is that this forces all users of these boards to > have this rather large carveout, even if they do not intend to use all > of these IP at the same time, or even at all. > > Actually, upstream we don't support GPU yet, so you can't use all of > this carveout anyway. > > Lastly, large CMA carveouts as in this case are masking a bigger issue, > there is hardware IP that cannot handle scatter-gather and there is > no system level IOMMU to help with that. This simply does not scale, > fragmentation can set in even with CMA in a running system, physically > contiguous allocations can still fail. As our devices grow in complexity > while still not having an IOMMU we would need to reserve ever increasingly > sized CMA areas. > Yes I think the CMA allocator tries to address the same scenarios and CMA reservation is needed to support use-cases with those hardware IP's. Also, I agree one magic value of CMA may not fit aptly all the users as some might not intend to use these IPs at all but a default value for CMA can be chosen to support basic use-cases supported by SoC, and if the setting doesn't suit the user they can override this setting using bootargs or some other method. > This might sound like an ad absurdum argument, but we only need to look > at our current evil vendor tree to see where this leads [0]. Yes you > are reading the size right, 1.75GB(!) of CMA.. > Hmm I don't have much context on large CMA there, but that board has 32Gb RAM :) > We need a better solution upstream, I'm not claiming I know what > that solution is (probably something involved in the memory allocation > to allow for more/larger movable pages). But for the above 3 reasons > this patch is not a viable solution. > Regarding movable pages, I think the CMA reservation uses pages allocated with MIGRATE_CMA [1] flag which ensure that it uses only the movable pages so reserved memory can be used by system if not used by driver and driver can reclaim it back when it requires. I am not sure what could be better solution than this, but I think camera and display are primary use-cases for AM625 and base device-tree will be enabling these peripherals by default and so the basic use-cases with them should also by supported out-of-box. My suggestion is to go with this approach and if somebody find better approach than this, we can update to it at that time. The alternatives I see are having a shared dma pool between a set of peripherals but that will require each driver using it to call of_reserved_mem_device_init(dev) before starting allocation and prevent other drivers (those not linked with this reserved region) from using CMA, and so I did not prefer that approach and prefer the base approach as shared in this patch. Kindly let me know your opinion. [0] https://devicetree-specification.readthedocs.io/en/latest/chapter3-devicenodes.html#:~:text=If%20a%20linux%2Ccma%2Ddefault [1] https://elixir.bootlin.com/linux/latest/source/include/linux/mmzone.h#L62 Regards Devarsh > [0] > https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/tree/arch/arm64/boot/dts/ti/k3-am69-sk.dts?h=ti-linux-6.1.y#n48 > > Andrew > >> $grep -r cma-default arch/arm64/boot/dts >> arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts:276: >> linux,cma-default; >> arch/arm64/boot/dts/qcom/sc8280xp-crd.dts:222: >> linux,cma-default; >> arch/arm64/boot/dts/freescale/imx8mp-tqma8mpql-mba8mpxl.dts:201: >> linux,cma-default; >> arch/arm64/boot/dts/freescale/imx8ulp-evk.dts:32: >> linux,cma-default; >> arch/arm64/boot/dts/freescale/imx8-apalis-v1.1.dtsi:198: >> linux,cma-default; >> arch/arm64/boot/dts/freescale/imx8mm-tqma8mqml.dtsi:48: >> linux,cma-default; >> arch/arm64/boot/dts/freescale/imx8dxl-evk.dts:50: >> linux,cma-default; >> arch/arm64/boot/dts/freescale/imx93-tqma9352.dtsi:24: >> linux,cma-default; >> arch/arm64/boot/dts/freescale/imx8mq-tqma8mq.dtsi:59: >> linux,cma-default; >> arch/arm64/boot/dts/freescale/imx8mn-tqma8mqnl.dtsi:46: >> linux,cma-default; >> arch/arm64/boot/dts/freescale/imx93-11x11-evk.dts:28: >> linux,cma-default; >> arch/arm64/boot/dts/hisilicon/hi6220-hikey.dts:67: >> linux,cma-default; >> arch/arm64/boot/dts/amlogic/meson-gx.dtsi:63: >> linux,cma-default; >> arch/arm64/boot/dts/amlogic/meson-g12-common.dtsi:121: >> linux,cma-default; >> arch/arm64/boot/dts/amlogic/meson-a1.dtsi:59: >> linux,cma-default; >> >> >> I am esp concerned since there are platforms based on >>> am62x and just 256MB DDR. >>> >> >> The file "k3-am62x-sk-common.dtsi" refers DDR memory size as 2Gb[1] and so I >> put CMA reservation in same file assuming all boards including this file have >> 2Gb. >> >> But if there are some boards having lesser DDR and including this >> k3-am62x-sk-common.dtsi and overriding memory node, I can put the CMA >> reservation node in board specific file i.e. k3-am625-sk.dts in V2. >> >> Kindly let me know if above is preferred approach. >> >> [1] >> https://gitlab.com/linux-kernel/linux-next/-/blob/next-20230807/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi?ref_type=tags#L33 >> >> Regards >> Devarsh >> >>>> arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi | 8 ++++++++ >>>> 1 file changed, 8 insertions(+) >>>> >>>> diff --git a/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi >>>> b/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi >>>> index 34c8ffc553ec..9dd6e23ca9ca 100644 >>>> --- a/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi >>>> +++ b/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi >>>> @@ -47,6 +47,14 @@ ramoops@9ca00000 { >>>> pmsg-size = <0x8000>; >>>> }; >>>> + /* global cma region */ >>>> + linux,cma { >>>> + compatible = "shared-dma-pool"; >>>> + reusable; >>>> + size = <0x00 0x8000000>; >>>> + linux,cma-default; >>>> + }; >>>> + >>>> secure_tfa_ddr: tfa@9e780000 { >>>> reg = <0x00 0x9e780000 0x00 0x80000>; >>>> alignment = <0x1000>; >>>> -- >>>> 2.34.1 >>>> >>>
Hi Andrew, Vignesh, Nishanth, On 08/08/23 13:44, Devarsh Thakkar wrote: [...] >>>>> Reserve 128MiB of global CMA which is also marked as re-usable >>>>> so that OS can also use the same if peripheral drivers are not using the >>>>> same. >>>>> I wanted to re-initiate discussion on this. Per discussion with few of the maintainers in OSS 2023 Summit, the suggestion was either to have MMU in the devices or use the CMA region as done with this patch. There was not much traction for the idea/suggestion to have some updates in CMA API to dynamically increase the CMA region per the requirement (for e.g. move the MIGRATE_MOVABLE pages to CMA area dynamically). Also I see some efforts in the past made on that direction for introducing CMA_AGGRESSIVE Kconfig to allocate from ZONE_MOVEABLE but were not accepted [1] and nevertheless it still requires CMA region to be available to begin with and only gives a bit of extra margin for the CMA. My vote is still to use global cma region with re-usable flag (as done with this patch) and 128 MiB is well estimated per the use-cases AM62x EVM is meant to cater (the vendor specific kernel has been using it) and is very much needed to provided out-of-box experience as otherwise basic display and camera use-cases don't work out-of-box. Besides I see many other boards [presumably mmu-less] using a similar approach : $git grep linux,cma-default arch/ | wc 36 72 2538 Kindly let us know your opinion on this if we are aligned to proceed with this approach or not. [1]: https://lore.kernel.org/all/20141107070655.GA3486@bbox/ https://linux-mm.kvack.narkive.com/LCGSAqAp/patch-0-4-cma-aggressive-make-cma-memory-be-more-aggressive-about-allocation Regards Devarsh
diff --git a/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi b/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi index 34c8ffc553ec..9dd6e23ca9ca 100644 --- a/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi +++ b/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi @@ -47,6 +47,14 @@ ramoops@9ca00000 { pmsg-size = <0x8000>; }; + /* global cma region */ + linux,cma { + compatible = "shared-dma-pool"; + reusable; + size = <0x00 0x8000000>; + linux,cma-default; + }; + secure_tfa_ddr: tfa@9e780000 { reg = <0x00 0x9e780000 0x00 0x80000>; alignment = <0x1000>;