On 12-01-21, 16:54, Geert Uytterhoeven wrote:

Hi Vinod,

On Tue, Jan 12, 2021 at 11:36 AM Vinod Koul [off-list ref] wrote:

quoted

On 07-01-21, 19:15, Geert Uytterhoeven wrote:

quoted

The DMACs (both SYS-DMAC and RT-DMAC) on R-Car V3U differ slightly from
the DMACs on R-Car Gen2 and other R-Car Gen3 SoCs:
  1. The per-channel registers are located in a second register block.
     Add support for mapping the second block, using the appropriate
     offsets and stride.
  2. The common Channel Clear Register (DMACHCLR) was replaced by a
     per-channel register.
     Update rcar_dmac_chan_clear{,_all}() to handle this.
     As rcar_dmac_init() needs to clear the status before the individual
     channels are probed, channel index and base address initialization
     are moved forward.

Inspired by a patch in the BSP by Phong Hoang
[off-list ref].

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

quoted

quoted

--- a/drivers/dma/sh/rcar-dmac.c
+++ b/drivers/dma/sh/rcar-dmac.c

@@ -189,7 +189,7 @@ struct rcar_dmac_chan {
  * struct rcar_dmac - R-Car Gen2 DMA Controller
  * @engine: base DMA engine object
  * @dev: the hardware device
- * @iomem: remapped I/O memory base
+ * @iomem: remapped I/O memory bases (second is optional)
  * @n_channels: number of available channels
  * @channels: array of DMAC channels
  * @channels_mask: bitfield of which DMA channels are managed by this driver

@@ -198,7 +198,7 @@ struct rcar_dmac_chan {
 struct rcar_dmac {
      struct dma_device engine;
      struct device *dev;
-     void __iomem *iomem;
+     void __iomem *iomem[2];

do you forsee many more memory regions, if not then why not add second

No I don't. TBH, I didn't foresee this change either; you never know
what the hardware people have on their mind for the next SoC ;-)

quoted

region, that way changes in this patch will be lesser..?

I did consider that option.  However, doing so would imply that (a) the
code to map the memory regions can no longer be a loop, but has to be
unrolled manually, and (b) rcar_dmac_of_data.chan_reg_block can no
longer be used to index iomem[], but needs a conditional expression or
statement.

quoted

and it would be better to refer to a region by its name rather than
iomem[1]..

    - * @iomem: remapped I/O memory base
    + * @common_base: remapped common or combined I/O memory base
    + * @channel_base: remapped optional channel I/O memory base

    -     void __iomem *iomem;
    +     void __iomem *common_base;
    +     void __iomem *channel_base;

If you still think this is worthwhile, I can make these changes.

Either way suits me, TBH it is not a deal breaker, so i would leave it
upto you :)

-- 
~Vinod