On Tue, Feb 11, 2014 at 6:27 PM, Russell King - ARM Linux
<linux@xxxxxxxxxxxxxxxx> wrote:
> On Tue, Feb 11, 2014 at 03:33:09PM +0800, Dong Aisheng wrote:
>> It depends on both host and card that 1) if host is able to detect
>> SDIO interrupts without clock
>> and 2) if the card is able to send interrupt to host without clock.
>> If any one of both can't do that, we may need to tell host to not
>> do runtime suspend to prevent the clock from being disabled.
>> Or the SDIO interrupt may not work.
>>
>> The IMX esdhc/usdhc can not detect the SDIO interrupts sent from card
>> if the clock is disabled.
>> So we need such quirk to not allow runtime PM for SDIO cards.
>> Doesn't it make sense?
>
> That's strange. I have it working as of last night.
>
> Yes, I have to leave the AHB clock on so that the registers are readable,
> in the interrupt handler, and that's something I only do if the SDIO
> interrupt is enabled, but everything else gets disabled.
>
The ahb, ipg and per of usdhc are using the same clock.
Looking at arch/arm/boot/dts/imx6qdl.dtsi
usdhc2: usdhc@02194000 {
compatible = "fsl,imx6q-usdhc";
reg = <0x02194000 0x4000>;
interrupts = <0 23 0x04>;
clocks = <&clks 164>, <&clks 164>, <&clks 164>;
clock-names = "ipg", "ahb", "per";
bus-width = <4>;
status = "disabled";
};
That means enabling of ahb clock actually will make ipg and per also open.
Then card interrupts can be detected well.
You can measure the card clock(pin5) with a scope to double check it.
Regards
Dong Aisheng
> --
> FTTC broadband for 0.8mile line: 5.8Mbps down 500kbps up. Estimation
> in database were 13.1 to 19Mbit for a good line, about 7.5+ for a bad.
> Estimate before purchase was "up to 13.2Mbit".
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