[PATCH 0/1] Enable ddr modes on emmc2 of Raspberry Pi 4 B

[PATCH 0/1] Enable ddr modes on emmc2 of Raspberry Pi 4 B

[Tobias Schramm]

Currently both micro SD cards and eMMC storage attached to a Pi 4 are
running in single data rate mode only. However the controller used
supports dual data rate modes. This patch enables ddr modes for both
sd and mmc storage.

I've verified that there are no issues transferring data in ddr mode
using multiple micro SD cards and eMMC modules from different vendors.
Additionally I've checked signal integrity on the data lines at the micro
SD card slot and did not find any issues there either.

Tobias Schramm (1):
  ARM: dts: bcm2711: Enable ddr modes on emmc2 controller

 arch/arm/boot/dts/bcm2711-rpi-4-b.dts | 2 ++
 1 file changed, 2 insertions(+)

-- 
2.28.0

[PATCH 1/1] ARM: dts: bcm2711: Enable ddr modes on emmc2 controller

[Tobias Schramm]

This patch enables ddr modes for eMMC and SD storage on emmc2,
doubling transfer speed. Previously only single data rate modes were
used, wasting half the available throughput.
The bcm2711 supports both SD and eMMC storage using ddr modes. Testing
show that pcb layout of the Raspberry Pi 4 can support them, too.

Signed-off-by: Tobias Schramm <t.schramm@manjaro.org>
---
 arch/arm/boot/dts/bcm2711-rpi-4-b.dts | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm/boot/dts/bcm2711-rpi-4-b.dts b/arch/arm/boot/dts/bcm2711-rpi-4-b.dts
index 222d7825e1ab..8b61e258e906 100644
--- a/arch/arm/boot/dts/bcm2711-rpi-4-b.dts
+++ b/arch/arm/boot/dts/bcm2711-rpi-4-b.dts
@@ -191,6 +191,8 @@ &emmc2 {
 	vqmmc-supply = <&sd_io_1v8_reg>;
 	vmmc-supply = <&sd_vcc_reg>;
 	broken-cd;
+	mmc-ddr-3_3v;
+	sd-uhs-ddr50;
 	status = "okay";
 };
 
-- 
2.28.0

Re: [PATCH 1/1] ARM: dts: bcm2711: Enable ddr modes on emmc2 controller

[Florian Fainelli]

On 8/29/2020 4:15 PM, Tobias Schramm wrote:
> This patch enables ddr modes for eMMC and SD storage on emmc2,
> doubling transfer speed. Previously only single data rate modes were
> used, wasting half the available throughput.
> The bcm2711 supports both SD and eMMC storage using ddr modes. Testing
> show that pcb layout of the Raspberry Pi 4 can support them, too.
> 
> Signed-off-by: Tobias Schramm <t.schramm@manjaro.org>

This depends on Stefan's patch here:

https://lore.kernel.org/linux-arm-kernel/1598651234-29826-1-git-send-email-stefan.wahren@i2se.com/

I am fine with us taking the DTS patch, as long as they all land in 5.10 
at some point.

> ---
>   arch/arm/boot/dts/bcm2711-rpi-4-b.dts | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm/boot/dts/bcm2711-rpi-4-b.dts b/arch/arm/boot/dts/bcm2711-rpi-4-b.dts
> index 222d7825e1ab..8b61e258e906 100644
> --- a/arch/arm/boot/dts/bcm2711-rpi-4-b.dts
> +++ b/arch/arm/boot/dts/bcm2711-rpi-4-b.dts
> @@ -191,6 +191,8 @@ &emmc2 {
>   	vqmmc-supply = <&sd_io_1v8_reg>;
>   	vmmc-supply = <&sd_vcc_reg>;
>   	broken-cd;
> +	mmc-ddr-3_3v;
> +	sd-uhs-ddr50;
>   	status = "okay";
>   };
>   
> 

-- 
Florian