On Fri, Apr 19, 2024 at 06:57:47PM +0200, Christian Gmeiner wrote: > Am Di., 9. Apr. 2024 um 14:14 Uhr schrieb Greg Kroah-Hartman > <gregkh@xxxxxxxxxxxxxxxxxxx>: > > > > On Tue, Apr 09, 2024 at 02:06:05PM +0200, Pascal FONTAIN wrote: > > > From: Andrew Davis <afd@xxxxxx> > > > > > > This new export type exposes to userspace the SRAM area as a DMA-BUF > > > Heap, > > > this allows for allocations of DMA-BUFs that can be consumed by various > > > DMA-BUF supporting devices. > > > > > > Signed-off-by: Andrew Davis <afd@xxxxxx> > > > Tested-by: Pascal Fontain <pascal.fontain@xxxxxxxxxxxxx> > > > > When sending on a patch from someone else, you too must sign off on it > > as per our documenation. Please read it and understand what you are > > agreeing to when you do that for a new version please. > > > > > --- > > > drivers/misc/Kconfig | 7 + > > > drivers/misc/Makefile | 1 + > > > drivers/misc/sram-dma-heap.c | 246 +++++++++++++++++++++++++++++++++++ > > > drivers/misc/sram.c | 6 + > > > drivers/misc/sram.h | 16 +++ > > > 5 files changed, 276 insertions(+) > > > create mode 100644 drivers/misc/sram-dma-heap.c > > > > > > diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig > > > index 9e4ad4d61f06..e6674e913168 100644 > > > --- a/drivers/misc/Kconfig > > > +++ b/drivers/misc/Kconfig > > > @@ -448,6 +448,13 @@ config SRAM > > > config SRAM_EXEC > > > bool > > > > > > +config SRAM_DMA_HEAP > > > + bool "Export on-chip SRAM pools using DMA-Heaps" > > > + depends on DMABUF_HEAPS && SRAM > > > + help > > > + This driver allows the export of on-chip SRAM marked as both pool > > > + and exportable to userspace using the DMA-Heaps interface. > > > > What will use this in userspace? > > > > I could imagine a way it might be used. This implies it is not needed because no one actually has actually used it for anything, so why make this change? > Imagine a SoC like TI's AM64x series, where some cores (A53) run Linux > and others (R5F) are managed by remoteproc to > execute a RTOS. When it comes to efficiently exchanging large data > sets, the conventional method involves using rpmsg, > which has limitations due to message size and could potentially slow > down data transfer. However, an alternative > approach could be to allocate a sizable chunk of SRAM memory in > userspace. By utilizing memcpy() to copy data into > this memory, followed by a single rpmsg signal to notify the RTOS that > the data is ready, we can leverage the faster access > speed of SRAM compared to DDR from the remoteproc. Why is virtio not used instead? thanks, greg k-h
