linux-kernel - Re: [PATCH] mmc: dw_mmc: Disable low power mode if SDIO interrupts are used

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Date:	Mon, 23 Jul 2012 10:19:16 +0100
From:	Will Newton <will.newton@...il.com>
To:	Doug Anderson <dianders@...omium.org>
Cc:	linux-mmc@...r.kernel.org, Chris Ball <cjb@...top.org>,
	James Hogan <james.hogan@...tec.com>,
	Seungwon Jeon <tgih.jun@...sung.com>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mmc: dw_mmc: Disable low power mode if SDIO interrupts
 are used

On Mon, Jul 23, 2012 at 3:48 AM, Doug Anderson <dianders@...omium.org> wrote:
> On Sat, Jul 21, 2012 at 3:40 AM, Will Newton <will.newton@...il.com> wrote:
>>>  static void dw_mci_enable_sdio_irq(struct mmc_host *mmc, int enb)
>>>  {
>>>         struct dw_mci_slot *slot = mmc_priv(mmc);
>>> @@ -871,6 +896,14 @@ static void dw_mci_enable_sdio_irq(struct mmc_host *mmc, int enb)
>>>         /* Enable/disable Slot Specific SDIO interrupt */
>>>         int_mask = mci_readl(host, INTMASK);
>>>         if (enb) {
>>> +               /*
>>> +                * Turn off low power mode if it was enabled.  This is a bit of
>>> +                * a heavy operation and we disable / enable IRQs a lot, so
>>> +                * we'll leave them disabled; they will get re-enabled again in
>>> +                * dw_mci_setup_bus().
>>> +                */
>>> +               dw_mci_disable_low_power(mmc);
>>> +
>>
>> Is it safe to just disable low power here or could the setting be
>> overwritten in setup_bus?
>
> Very good question.  In my current setup I don't see setup_bus()
> called during normal operation.  If it were, my kernel messages would
> be constantly spammed with messages like:
>     Bus speed (slot %d) = %dHz (slot req %dHz, actual %dHZ div = %d)
>
> ...and they're not.  Things may be different with different SDIO cards perhaps?

Yeah I think setup_bus should only setup the card clock once at
startup but it may also be required on resume?

I should probably mention I have not tested this driver with any SDIO
devices, although I believe there are other people out there who do!
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