Re: [RFC 2/3] mmc: sdhci: add host_ops->voltage_switch callback for all other voltages

From: Vaibhav Hiremath
Date: Wed Sep 02 2015 - 07:44:15 EST

On Wednesday 02 September 2015 01:56 PM, Jisheng Zhang wrote:
On Wed, 2 Sep 2015 13:49:53 +0530
Vaibhav Hiremath <vaibhav.hiremath@xxxxxxxxxx> wrote:

On Wednesday 02 September 2015 12:34 PM, Jisheng Zhang wrote:
On Wed, 2 Sep 2015 01:02:17 +0530
Vaibhav Hiremath <vaibhav.hiremath@xxxxxxxxxx> 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@xxxxxxxxxx>
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.

Not quite sure whether regulator would be right fit for this.

From the patche[3/3], this can be achieved by abstracting the IO PAD as regulators
then, we may not need to touch the core sdhci.c. But I'm not sure whether this
is the good solution or not.


sdhci Maintainers and experts may have better

Thats is the reason I stamped it as a RFC :)

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