Correct DT properties for Arasan controller

Correct DT properties for Arasan controller

[Marc Gonzalez]

Hello everyone,

My SoC provides an "SD3.0 / SDIO3.0 / eMMC4.4 AHB Host Controller"
from Arasan Chip Systems (data sheet says rev 6.0, dated Feb 2010).

There are two instances of the controller:
mmc0 is wired to an SD card reader,
mmc1 is wired to an eMMC chip.

I'm trying to figure out how to write the DT.
(Currently using Linux 4.2)

This is what I have so far:

		mmc0: mmc@21000 {
			compatible = "arasan,sdhci-8.9a";
			reg = <0x21000 0x200>;
			clock-names = "clk_xin", "clk_ahb";
			clocks = <&sdio_clk>, <&clkgen 1>;
			interrupts = <60 IRQ_TYPE_LEVEL_HIGH>;
			bus-width = <8>;
			cap-sd-highspeed;
			sd-uhs-sdr12;
			sd-uhs-sdr25;
			sd-uhs-sdr50;
			sd-uhs-ddr50;
			sd-uhs-sdr104;
		};

		mmc1: mmc@21200 {
			compatible = "arasan,sdhci-8.9a";
			reg = <0x21200 0x200>;
			clock-names = "clk_xin", "clk_ahb";
			clocks = <&sdio_clk>, <&clkgen 1>;
			interrupts = <8 IRQ_TYPE_LEVEL_HIGH>;
			bus-width = <8>;
			non-removable;
		};

https://www.kernel.org/doc/Documentation/devicetree/bindings/mmc/mmc.txt

(I don't know anything about MMC, SDHCI, SDIO, etc.)

Are cap-sd-highspeed and sd-uhs-* limited to mmc0? (wired to SD card reader)

Are cap-mmc-highspeed and mmc-* limited to mmc1? (wired to eMMC)

What about these?
- bus-width: Number of data lines, can be <1>, <4>, or <8>.  The default
  will be <1> if the property is absent.
- cap-power-off-card: powering off the card is safe
- cap-mmc-hw-reset: eMMC hardware reset is supported
- cap-sdio-irq: enable SDIO IRQ signalling on this interface
- full-pwr-cycle: full power cycle of the card is supported

Also, I set clk_xin to 48 MHz (and clk_ahb is set to 400 MHz).
Does clk_xin need to be higher for the faster modes?

Regards.

Re: Correct DT properties for Arasan controller

[Arnd Bergmann]

On Thursday 19 November 2015 17:37:13 Marc Gonzalez wrote:
> Hello everyone,
> 
> My SoC provides an "SD3.0 / SDIO3.0 / eMMC4.4 AHB Host Controller"
> from Arasan Chip Systems (data sheet says rev 6.0, dated Feb 2010).
> 
> There are two instances of the controller:
> mmc0 is wired to an SD card reader,
> mmc1 is wired to an eMMC chip.
> 
> I'm trying to figure out how to write the DT.
> (Currently using Linux 4.2)
> 
> This is what I have so far:
> 
> 		mmc0: mmc@21000 {
> 			compatible = "arasan,sdhci-8.9a";

make this "arasan,sdhci-6.0", plus a chip specific string
in front of it.

> 			reg = <0x21000 0x200>;
> 			clock-names = "clk_xin", "clk_ahb";
> 			clocks = <&sdio_clk>, <&clkgen 1>;
> 			interrupts = <60 IRQ_TYPE_LEVEL_HIGH>;
> 			bus-width = <8>;
> 			cap-sd-highspeed;
> 			sd-uhs-sdr12;
> 			sd-uhs-sdr25;
> 			sd-uhs-sdr50;
> 			sd-uhs-ddr50;
> 			sd-uhs-sdr104;
> 		};
> 
> 		mmc1: mmc@21200 {
> 			compatible = "arasan,sdhci-8.9a";
> 			reg = <0x21200 0x200>;
> 			clock-names = "clk_xin", "clk_ahb";
> 			clocks = <&sdio_clk>, <&clkgen 1>;
> 			interrupts = <8 IRQ_TYPE_LEVEL_HIGH>;
> 			bus-width = <8>;
> 			non-removable;
> 		};
> 
> https://www.kernel.org/doc/Documentation/devicetree/bindings/mmc/mmc.txt
> 
> (I don't know anything about MMC, SDHCI, SDIO, etc.)
> 
> Are cap-sd-highspeed and sd-uhs-* limited to mmc0? (wired to SD card reader)
> 
> Are cap-mmc-highspeed and mmc-* limited to mmc1? (wired to eMMC)

It depends: if the wiring is board specific, put them into the .dts file
and put the generic properties (interrupts, clocks, reg, compatible)
into the .dtsi file.

> What about these?
> - bus-width: Number of data lines, can be <1>, <4>, or <8>.  The default
>   will be <1> if the property is absent.

board specific

> - cap-power-off-card: powering off the card is safe
> - cap-mmc-hw-reset: eMMC hardware reset is supported
> - cap-sdio-irq: enable SDIO IRQ signalling on this interface
> - full-pwr-cycle: full power cycle of the card is supported
> 
> Also, I set clk_xin to 48 MHz (and clk_ahb is set to 400 MHz).
> Does clk_xin need to be higher for the faster modes?

don't know. I think the clock gets set by the driver, so the
clock controller needs to be programmable.

	Arnd

Re: Correct DT properties for Arasan controller

[Alan Cooper]

On Thu, Nov 19, 2015 at 3:56 PM, Arnd Bergmann <arnd@arndb.de> wrote:
>>                       cap-sd-highspeed;
>>                       sd-uhs-sdr12;
>>                       sd-uhs-sdr25;
>>                       sd-uhs-sdr50;
>>                       sd-uhs-ddr50;
>>                       sd-uhs-sdr104;

These values normally come from the Host Controllers CAPS registers
and are only needed if the CAPS register setting are incorrect.

>> - cap-mmc-hw-reset: eMMC hardware reset is supported

This is only set if the driver supplies a hw_reset callback and the
Arasan driver does not.

>> - cap-sdio-irq: enable SDIO IRQ signalling on this interface

This is only set if the driver supplies a enable_sdio_irq and the
Arasan driver does not.



Al

Re: Correct DT properties for Arasan controller

[Marc Gonzalez]

On 19/11/2015 22:42, Alan Cooper wrote:

>>>                       cap-sd-highspeed;
>>>                       sd-uhs-sdr12;
>>>                       sd-uhs-sdr25;
>>>                       sd-uhs-sdr50;
>>>                       sd-uhs-ddr50;
>>>                       sd-uhs-sdr104;
> 
> These values normally come from the Host Controllers CAPS registers
> and are only needed if the CAPS register setting are incorrect.

Using a 4 GB microSDHC card + SD adapter, I get read speeds of
17.3 MB/s (4072669184 bytes in 236 seconds).
Is that an expected value? SDR25 should be 25 MB/s.
Perhaps I need to buy a better card.

>>> - cap-mmc-hw-reset: eMMC hardware reset is supported
> 
> This is only set if the driver supplies a hw_reset callback and the
> Arasan driver does not.

OK.

>>> - cap-sdio-irq: enable SDIO IRQ signalling on this interface
> 
> This is only set if the driver supplies a enable_sdio_irq and the
> Arasan driver does not.

Can't it use a generic implementation, such as sdhci_enable_sdio_irq?

Regards.

Re: Correct DT properties for Arasan controller

[Marc Gonzalez]

On 19/11/2015 21:56, Arnd Bergmann wrote:
> On Thursday 19 November 2015 17:37:13 Marc Gonzalez wrote:
>> Hello everyone,
>>
>> My SoC provides an "SD3.0 / SDIO3.0 / eMMC4.4 AHB Host Controller"
>> from Arasan Chip Systems (data sheet says rev 6.0, dated Feb 2010).
>>
>> There are two instances of the controller:
>> mmc0 is wired to an SD card reader,
>> mmc1 is wired to an eMMC chip.
>>
>> I'm trying to figure out how to write the DT.
>> (Currently using Linux 4.2)
>>
>> This is what I have so far:
>>
>> 		mmc0: mmc@21000 {
>> 			compatible = "arasan,sdhci-8.9a";
> 
> make this "arasan,sdhci-6.0", plus a chip specific string
> in front of it.

Sorry, I wasn't clear...
6.0 is the revision of the documentation, not of the hardware block.
(Actually, I don't know what 4.9a and 8.9a refer to.
Does anyone know?)

>> 			reg = <0x21000 0x200>;
>> 			clock-names = "clk_xin", "clk_ahb";
>> 			clocks = <&sdio_clk>, <&clkgen 1>;
>> 			interrupts = <60 IRQ_TYPE_LEVEL_HIGH>;
>> 			bus-width = <8>;
>> 			cap-sd-highspeed;
>> 			sd-uhs-sdr12;
>> 			sd-uhs-sdr25;
>> 			sd-uhs-sdr50;
>> 			sd-uhs-ddr50;
>> 			sd-uhs-sdr104;
>> 		};
>>
>> 		mmc1: mmc@21200 {
>> 			compatible = "arasan,sdhci-8.9a";
>> 			reg = <0x21200 0x200>;
>> 			clock-names = "clk_xin", "clk_ahb";
>> 			clocks = <&sdio_clk>, <&clkgen 1>;
>> 			interrupts = <8 IRQ_TYPE_LEVEL_HIGH>;
>> 			bus-width = <8>;
>> 			non-removable;
>> 		};
>>
>> https://www.kernel.org/doc/Documentation/devicetree/bindings/mmc/mmc.txt
>>
>> (I don't know anything about MMC, SDHCI, SDIO, etc.)
>>
>> Are cap-sd-highspeed and sd-uhs-* limited to mmc0? (wired to SD card reader)
>>
>> Are cap-mmc-highspeed and mmc-* limited to mmc1? (wired to eMMC)
> 
> It depends: if the wiring is board specific, put them into the .dts file
> and put the generic properties (interrupts, clocks, reg, compatible)
> into the .dtsi file.

Hmmm, sorry again. I was not asking where to put them. I was asking
if I should only use sd-uhs-* properties for an SD card reader node?

And should I only use mmc-* for an eMMC node?

>> What about these?
>> - bus-width: Number of data lines, can be <1>, <4>, or <8>.  The default
>>   will be <1> if the property is absent.
> 
> board specific

HW guy tells me the controller handles 8 bits. Do you mean that the
board could actually use only 1 or 4 wires?

>> - cap-power-off-card: powering off the card is safe
>> - cap-mmc-hw-reset: eMMC hardware reset is supported
>> - cap-sdio-irq: enable SDIO IRQ signalling on this interface
>> - full-pwr-cycle: full power cycle of the card is supported
>>
>> Also, I set clk_xin to 48 MHz (and clk_ahb is set to 400 MHz).
>> Does clk_xin need to be higher for the faster modes?
> 
> don't know. I think the clock gets set by the driver, so the
> clock controller needs to be programmable.

The input clock is definitely not programmable. I see a clock
divider inside the controller (SDCLK Frequency Select)

I also see "00h - base clock (10MHz-63MHz)"

However, elsewhere the doc states:

> clk_xin - Input SD Clock used to generate SD Clock based on the
> divisor value programmed by the Host Driver. This SD clock input is
> used to generate SD Clock. This clock is also used to derive Sleep
> clock used to detect Card insertion / removal.
> For maximum efficiency > this should be around 52 MHz (for MMC) /
> 208Mhz (for SD3.0) / 50Mhz (for SD2.0)

Since the controller supports SD3.0, I'm wondering if I should use
a faster clock for that.

Regards.