lkml.org 
[lkml]   [2020]   [May]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH v5 09/11] dmaengine: dw: Initialize min and max burst DMA device capability
    On Fri, May 29, 2020 at 05:40:52PM +0300, Serge Semin wrote:
    > According to the DW APB DMAC data book the minimum burst transaction
    > length is 1 and it's true for any version of the controller since
    > isn't parametrised in the coreAssembler so can't be changed at the
    > IP-core synthesis stage. The maximum burst transaction can vary from
    > channel to channel and from controller to controller depending on a
    > IP-core parameter the system engineer activated during the IP-core
    > synthesis. Let's initialise both min_burst and max_burst members of the
    > DMA controller descriptor with extreme values so the DMA clients could
    > use them to properly optimize the DMA requests. The channels and
    > controller-specific max_burst length initialization will be introduced
    > by the follow-up patches.

    Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

    > Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
    > Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
    > Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
    > Cc: Arnd Bergmann <arnd@arndb.de>
    > Cc: Rob Herring <robh+dt@kernel.org>
    > Cc: linux-mips@vger.kernel.org
    > Cc: devicetree@vger.kernel.org
    >
    > ---
    >
    > Changelog v4:
    > - This is a new patch suggested by Andy.
    >
    > Changelog v5:
    > - Introduce macro with extreme min and max burst length supported by the
    > DW DMA controller.
    > - Initialize max_burst length capability with extreme burst length supported
    > by the DW DMAC IP-core.
    > ---
    > drivers/dma/dw/core.c | 2 ++
    > include/linux/platform_data/dma-dw.h | 2 ++
    > 2 files changed, 4 insertions(+)
    >
    > diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c
    > index ceded21537e2..4887aa2fc73c 100644
    > --- a/drivers/dma/dw/core.c
    > +++ b/drivers/dma/dw/core.c
    > @@ -1229,6 +1229,8 @@ int do_dma_probe(struct dw_dma_chip *chip)
    > dw->dma.device_issue_pending = dwc_issue_pending;
    >
    > /* DMA capabilities */
    > + dw->dma.min_burst = DW_DMA_MIN_BURST;
    > + dw->dma.max_burst = DW_DMA_MAX_BURST;
    > dw->dma.src_addr_widths = DW_DMA_BUSWIDTHS;
    > dw->dma.dst_addr_widths = DW_DMA_BUSWIDTHS;
    > dw->dma.directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV) |
    > diff --git a/include/linux/platform_data/dma-dw.h b/include/linux/platform_data/dma-dw.h
    > index f3eaf9ec00a1..369e41e9dcc9 100644
    > --- a/include/linux/platform_data/dma-dw.h
    > +++ b/include/linux/platform_data/dma-dw.h
    > @@ -12,6 +12,8 @@
    >
    > #define DW_DMA_MAX_NR_MASTERS 4
    > #define DW_DMA_MAX_NR_CHANNELS 8
    > +#define DW_DMA_MIN_BURST 1
    > +#define DW_DMA_MAX_BURST 256
    >
    > /**
    > * struct dw_dma_slave - Controller-specific information about a slave
    > --
    > 2.26.2
    >

    --
    With Best Regards,
    Andy Shevchenko


    \
     
     \ /
      Last update: 2020-05-29 17:49    [W:2.755 / U:0.160 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site