linux-kernel - Re: [RFC 2/3] mmc: sdhci: add host_ops->voltage

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Message-ID: <20150902150442.118d3305@xhacker>
Date:	Wed, 2 Sep 2015 15:04:42 +0800
From:	Jisheng Zhang <jszhang@...vell.com>
To:	Vaibhav Hiremath <vaibhav.hiremath@...aro.org>
CC:	<linux-mmc@...r.kernel.org>, <ulf.hansson@...aro.org>,
	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC 2/3] mmc: sdhci: add host_ops->voltage_switch callback for
 all other voltages

On Wed, 2 Sep 2015 01:02:17 +0530
Vaibhav Hiremath <vaibhav.hiremath@...aro.org> wrote:

> Currently, the sdhci_do_start_signal_voltage_switch() function invokes
> controller specific voltage switch configuration only for 1.8v usecase;
> but it is required for others as well.
> 
> For example, in case of PXA1928 SDH controller, we need to set different
> configuration for 3.3, 1.8 and 1.2 volt support (I/O domain power
> control register).
> 
> Signed-off-by: Vaibhav Hiremath <vaibhav.hiremath@...aro.org>
> ---
> Note:
> Currently ->voltage_switch() callback is only supported
> in f_sdh30 driver. And I am not sure on the dependency of execution
> sequence for that device. I could have moved ->voltage_switch() call
> at one common place (above/below), but was not quite sure about it.
> So, replicated/duplicated the call for other voltages.
> 
>  drivers/mmc/host/sdhci.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 3dd295f..b59b76d 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -1753,6 +1753,10 @@ static int sdhci_do_start_signal_voltage_switch(struct sdhci_host *host,
>  		/* Wait for 5ms */
>  		usleep_range(5000, 5500);
>  
> +		/* Some controller need to do more when switching */
> +		if (host->ops->voltage_switch)
> +			host->ops->voltage_switch(host, MMC_SIGNAL_VOLTAGE_330);

Could this be implemented by regulator API? From patch set 3/3, the pxa1928
voltage_switch hook is to operate the IO pad registers, this seems not belong
to the SDHC IP core.

Thanks,
Jisheng

> +
>  		/* 3.3V regulator output should be stable within 5 ms */
>  		ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
>  		if (!(ctrl & SDHCI_CTRL_VDD_180))
> @@ -1803,6 +1807,10 @@ static int sdhci_do_start_signal_voltage_switch(struct sdhci_host *host,
>  				return -EIO;
>  			}
>  		}
> +		/* Some controller need to do more when switching */
> +		if (host->ops->voltage_switch)
> +			host->ops->voltage_switch(host, MMC_SIGNAL_VOLTAGE_120);
> +
>  		return 0;
>  	default:
>  		/* No signal voltage switch required */

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