Re: [PATCH 1/2] dt-bindings: mmc: mtk-sd: add single burst switch

On Fri, 2025-03-07 at 15:48 +0000, Conor Dooley wrote:

On Fri, Mar 07, 2025 at 06:59:03AM +0000, Axe Yang (杨磊) wrote:

quoted

On Thu, 2025-03-06 at 10:19 +0100, AngeloGioacchino Del Regno
wrote:

quoted

External email : Please do not click links or open attachments
until
you have verified the sender or the content.


Il 06/03/25 09:48, Axe Yang ha scritto:

quoted

Add 'mediatek,disable-single-burst' setting. This property can
be
used to switch bus burst type, from single burst to INCR, which
is
determined by the bus type within the IP. Some versions of the
IP
are using AXI bus, thus this switch is necessary as 'single' is
not
the burst type supported by the bus.

Signed-off-by: Axe Yang <redacted>

I am mostly sure that this is not something to put in devicetree,
but
as
platform data for specific SoC(s), as much as I'm mostly sure
that
all of
the instances of the MSDC IP in one SoC will be *all* using
either
single
or INCR.

No, actually MSDC IPs in one SoC are using different versions.
Usually MSDC1 (index from 1) is used as eMMC host, the left hosts
are
used as SD/SDIO hosts. They have similar designs, but there are
still
difference.

quoted

So, I think I know the answer but I'll still ask just to be
extremely
sure:

is there any MediaTek SoC that has different IP versions for
different MSDC
instances, and that hence require single burst on one instance
and
INCR on
another instance?

Yes. Actually every SoC has different IP versions for eMMC and
SD/SDIO
host as I said.
e.g. For MT8168, signel burst bit should be set to 1 for eMMC Host,
but
0 for SD/SDIO Host.

Sounds like two different IPs that really should have different
compatibles to me...

Yes, so considering all factors, adding a device tree property might be
the most appropriate approach. This method is more flexible and
convenient.
Another reason, which I didn't mention in the previous reply, is that
MediaTek has too many SoCs using MSDC. Currently, there are already 13
mtXXXX compatible structures in the msdc driver, and a significant
portion of the SoC settings can be reused by the new SoC (without
adding a compatible for new SoC). 
If we add a variable in the compatible to represent the single burst
setting for eMMC/SD/SDIO (maybe using a u8 type variable as bitmap for
different hosts, bit0 for msdc0, bit1 for msdc1, bit2 for msdc2, ...),
we might have to add a compatible for each Soc, leading to a
significant increase in the number of compatibles and making it more
complex.

Regards,
Axe

quoted

quoted

And if there is - is there a pattern? Is it always SDIO requiring
INCR or
always eMMC/SD requiring it?

No, there is no pattern. Both eMMC and SD/SDIO hosts need to be
configured base on IP version. There is no binding relationship
between
eMMC/SD/SDIO and the burst type. eMMC burst type might be INCR or
single, same as SD/SDIO.


Regards,
Axe

quoted

quoted

---
  Documentation/devicetree/bindings/mmc/mtk-sd.yaml | 8
++++++++
  1 file changed, 8 insertions(+)

diff --git a/Documentation/devicetree/bindings/mmc/mtk-sd.yaml

b/Documentation/devicetree/bindings/mmc/mtk-sd.yaml
index 0debccbd6519..6076aff0a689 100644

--- a/Documentation/devicetree/bindings/mmc/mtk-sd.yaml
+++ b/Documentation/devicetree/bindings/mmc/mtk-sd.yaml

@@ -100,6 +100,14 @@ properties:
      minimum: 0
      maximum: 0xffffffff

+  mediatek,disable-single-burst:
+    $ref: /schemas/types.yaml#/definitions/flag
+    description:
+      Burst type setting. For some versions of the IP that do

not
use
+      AHB bus, the burst type need to be switched to INCR.
+      If present, use INCR burst type.
+      If not present, use single burst type.
+
    mediatek,hs200-cmd-int-delay:
      $ref: /schemas/types.yaml#/definitions/uint32
      description: