| Message ID | 20200124092359.12429-1-peter.ujfalusi@ti.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: defconfig: Enable Texas Instruments UDMA driver | expand |
On Fri, Jan 24, 2020 at 11:23:59AM +0200, Peter Ujfalusi wrote: > The UDMA driver is used on K3 platforms (am654 and j721e). > > Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com> > --- > Hi, > > The drivers for UDMA are already in linu-next and the DT patches are going to be > also heading for 5.6. > The only missing piece is to enable the drivers in defconfig so clients can use > the DMA. Hi Peter, We normally like to see new options turned on after the driver/option has been merged, so send this during or right after the merge window when that happens, please. I also see that this is statically enabling this driver -- we try to keep as many drivers as possible as modules to avoid the static kernel from growing too large. Would that be a suitable approach here, or is the driver needed to reach rootfs for further module loading? Thanks, -Olof
Hi Olof, On 24/01/2020 22.08, Olof Johansson wrote: > On Fri, Jan 24, 2020 at 11:23:59AM +0200, Peter Ujfalusi wrote: >> The UDMA driver is used on K3 platforms (am654 and j721e). >> >> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com> >> --- >> Hi, >> >> The drivers for UDMA are already in linu-next and the DT patches are going to be >> also heading for 5.6. >> The only missing piece is to enable the drivers in defconfig so clients can use >> the DMA. > > Hi Peter, > > We normally like to see new options turned on after the driver/option has been > merged, so send this during or right after the merge window when that happens, > please. Sure, I'll post it later. > I also see that this is statically enabling this driver -- we try to keep as > many drivers as possible as modules to avoid the static kernel from growing too > large. Would that be a suitable approach here, or is the driver needed to reach > rootfs for further module loading? We would need built in DMA for nfs rootfs, SD/MMC has it's own buit-in ADMA. We do not have network drivers upstream as they depend on the DMA. Imho module would be fine for the DMA stack, but neither ringacc or the UDMA driver can be built as module atm until the following patches got merged: https://lore.kernel.org/lkml/20200122104723.16955-1-peter.ujfalusi@ti.com/ https://lore.kernel.org/lkml/20200122104031.15733-1-peter.ujfalusi@ti.com/ I have the patches to add back module support, but waiting on these currently. - Péter Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
On Mon, Jan 27, 2020 at 2:31 AM Peter Ujfalusi <peter.ujfalusi@ti.com> wrote: > > Hi Olof, > > On 24/01/2020 22.08, Olof Johansson wrote: > > On Fri, Jan 24, 2020 at 11:23:59AM +0200, Peter Ujfalusi wrote: > >> The UDMA driver is used on K3 platforms (am654 and j721e). > >> > >> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com> > >> --- > >> Hi, > >> > >> The drivers for UDMA are already in linu-next and the DT patches are going to be > >> also heading for 5.6. > >> The only missing piece is to enable the drivers in defconfig so clients can use > >> the DMA. > > > > Hi Peter, > > > > We normally like to see new options turned on after the driver/option has been > > merged, so send this during or right after the merge window when that happens, > > please. > > Sure, I'll post it later. Great! > > > I also see that this is statically enabling this driver -- we try to keep as > > many drivers as possible as modules to avoid the static kernel from growing too > > large. Would that be a suitable approach here, or is the driver needed to reach > > rootfs for further module loading? > > We would need built in DMA for nfs rootfs, SD/MMC has it's own buit-in > ADMA. We do not have network drivers upstream as they depend on the DMA. Ok, so that can either be turned into a ramdisk argument, or into a "we really want to enable non-ramdisk rootfs boots on this hardware because it's a common use case". I find it useful to challenge most of the =y drivers to make people think about it, and at some point we'll enough overhead of cruft in the static superset kernel that defconfig today is used for such that we need to prune more =y -> =m, but this particular driver is probably OK (it's also not large). > Imho module would be fine for the DMA stack, but neither ringacc or the > UDMA driver can be built as module atm until the following patches got > merged: > https://lore.kernel.org/lkml/20200122104723.16955-1-peter.ujfalusi@ti.com/ > https://lore.kernel.org/lkml/20200122104031.15733-1-peter.ujfalusi@ti.com/ > > I have the patches to add back module support, but waiting on these > currently. -Olof
Hi Olof, On 27/01/2020 17.30, Olof Johansson wrote: >>> I also see that this is statically enabling this driver -- we try to keep as >>> many drivers as possible as modules to avoid the static kernel from growing too >>> large. Would that be a suitable approach here, or is the driver needed to reach >>> rootfs for further module loading? >> >> We would need built in DMA for nfs rootfs, SD/MMC has it's own buit-in >> ADMA. We do not have network drivers upstream as they depend on the DMA. > > Ok, so that can either be turned into a ramdisk argument, or into a > "we really want to enable non-ramdisk rootfs boots on this hardware > because it's a common use case". SD/MMC does not need slave DMA, it is self containing with it's own built-in DMA. I'm not sure if it is enabled in defconfig. It is not enabled at all in defconfig atm. Normally I would use nfs rootfs, but we don't have network drivers upstream for K3 platform. I think having the UDMA stack as module should be fine when I have the dependencies in to be able to build them as modules. > I find it useful to challenge most of the =y drivers to make people > think about it, and at some point we'll enough overhead of cruft in > the static superset kernel that defconfig today is used for such that > we need to prune more =y -> =m, Sure, I fully agree on this, we should have non boot needed drivers as modules. > but this particular driver is probably > OK (it's also not large). Well, it depends how you look at it ;) UDMA stack is not enabled in defconfig (w/o this patch): $ size vmlinux text data bss dec hex filename 17853717 9221872 469288 27544877 1a44d2d vmlinux UDMA stack is enabled in defconfig (w this patch): $ size vmlinux text data bss dec hex filename 17890970 9237544 469288 27597802 1a51bea vmlinux It would be nice for other driver to enable the DMA if it is acceptable to have it built in for start and when I can build it as module we can switch it to module? >> Imho module would be fine for the DMA stack, but neither ringacc or the >> UDMA driver can be built as module atm until the following patches got >> merged: >> https://lore.kernel.org/lkml/20200122104723.16955-1-peter.ujfalusi@ti.com/ >> https://lore.kernel.org/lkml/20200122104031.15733-1-peter.ujfalusi@ti.com/ >> >> I have the patches to add back module support, but waiting on these >> currently. > > -Olof > - Péter Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
On Tue, Jan 28, 2020 at 9:20 AM Peter Ujfalusi <peter.ujfalusi@ti.com> wrote: > On 27/01/2020 17.30, Olof Johansson wrote: > >>> I also see that this is statically enabling this driver -- we try to keep as > >>> many drivers as possible as modules to avoid the static kernel from growing too > >>> large. Would that be a suitable approach here, or is the driver needed to reach > >>> rootfs for further module loading? > >> > >> We would need built in DMA for nfs rootfs, SD/MMC has it's own buit-in > >> ADMA. We do not have network drivers upstream as they depend on the DMA. > > > > Ok, so that can either be turned into a ramdisk argument, or into a > > "we really want to enable non-ramdisk rootfs boots on this hardware > > because it's a common use case". > > SD/MMC does not need slave DMA, it is self containing with it's own > built-in DMA. > I'm not sure if it is enabled in defconfig. It is not enabled at all in > defconfig atm. > > Normally I would use nfs rootfs, but we don't have network drivers > upstream for K3 platform. > > I think having the UDMA stack as module should be fine when I have the > dependencies in to be able to build them as modules. Picking up this thread as I noticed the patch is still marked as 'New' in patchwork. I see no problem making this driver built-in at all if you want to respin it. > > but this particular driver is probably > > OK (it's also not large). > > Well, it depends how you look at it ;) > > UDMA stack is not enabled in defconfig (w/o this patch): > $ size vmlinux > text data bss dec hex filename > 17853717 9221872 469288 27544877 1a44d2d vmlinux > > UDMA stack is enabled in defconfig (w this patch): > $ size vmlinux > text data bss dec hex filename > 17890970 9237544 469288 27597802 1a51bea vmlinux > > It would be nice for other driver to enable the DMA if it is acceptable > to have it built in for start and when I can build it as module we can > switch it to module? In general, I'd prefer to avoid listing references to other drivers in Kconfig when those are only runtime dependencies rather than compile-time. If the network driver just uses the generic dma slave API, then I would not add a 'depends on' or 'select' for the particular DMA engine that it uses, unless it relies on nonstandard exported functions from that driver. Just enable both as modules and have the runtime module loading along with deferred probe figure out runtime dependency. Arnd
diff --git a/arch/arm64/configs/defconfig b/arch/arm64/configs/defconfig index 4631a1190719..a325a296d94c 100644 --- a/arch/arm64/configs/defconfig +++ b/arch/arm64/configs/defconfig @@ -698,6 +698,7 @@ CONFIG_QCOM_HIDMA_MGMT=y CONFIG_QCOM_HIDMA=y CONFIG_RCAR_DMAC=y CONFIG_RENESAS_USB_DMAC=m +CONFIG_TI_K3_UDMA=y CONFIG_VFIO=y CONFIG_VFIO_PCI=y CONFIG_VIRTIO_PCI=y
The UDMA driver is used on K3 platforms (am654 and j721e). Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com> --- Hi, The drivers for UDMA are already in linu-next and the DT patches are going to be also heading for 5.6. The only missing piece is to enable the drivers in defconfig so clients can use the DMA. Regards, Peter arch/arm64/configs/defconfig | 1 + 1 file changed, 1 insertion(+)