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SubjectRe: [PATCH v4] mmc: mxs-mmc: Introduce regulator support
On Thu, 31 Jan 2019 13:17:23 +0100
Ulf Hansson <ulf.hansson@linaro.org> wrote:

> On Thu, 31 Jan 2019 at 09:20, Robin van der Gracht <robin@protonic.nl> wrote:
> >
> > On Mon, 28 Jan 2019 22:15:23 +0100
> > Ulf Hansson <ulf.hansson@linaro.org> wrote:
> >
> > > On Mon, 28 Jan 2019 at 15:41, Martin Kepplinger <martink@posteo.de> wrote:
> > > >
> > > > From: Martin Kepplinger <martin.kepplinger@ginzinger.com>
> > > >
> > > > This adds support for explicitly switching the mmc's power on and off
> > > > which is needed for example for WL1837 WL1271 wifi controllers on imx28.
> > > >
> > > > While the wifi's vmmc-supply regulator can be configured in devicetree,
> > > > "ip link set wlan0 down" doesn't turn off the VMMC regulator which leads
> > > > to hangs when loading firmware, for example.
> > > >
> > > > Signed-off-by: Martin Kepplinger <martin.kepplinger@ginzinger.com>
> > > > ---
> > > >
> > > >
> > > > revision history
> > > > ----------------
> > > > v4: re-added forgotten regulator_enable() during probe
> > > > v3: improve API usage as suggested by Ulf
> > > > v2: tested patch with changes suggested by Robin
> > > > v1: question, why https://patchwork.kernel.org/patch/4365751/ didn't get in
> > > >
> > > >
> > > > drivers/mmc/host/mxs-mmc.c | 34 +++++++++++++++++++++++++---------
> > > > 1 file changed, 25 insertions(+), 9 deletions(-)
> > > >
> > > > diff --git a/drivers/mmc/host/mxs-mmc.c b/drivers/mmc/host/mxs-mmc.c
> > > > index add1e70195ea..23d275269d61 100644
> > > > --- a/drivers/mmc/host/mxs-mmc.c
> > > > +++ b/drivers/mmc/host/mxs-mmc.c
> > > > @@ -517,6 +517,22 @@ static void mxs_mmc_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
> > > > else
> > > > host->bus_width = 0;
> > > >
> > > > + switch (ios->power_mode) {
> > > > + case MMC_POWER_OFF:
> > > > + if (!IS_ERR(host->mmc->supply.vmmc))
> > > > + mmc_regulator_set_ocr(host->mmc,
> > > > + host->mmc->supply.vmmc, 0);
> > > > + break;
> > > > + case MMC_POWER_UP:
> > > > + if (!IS_ERR(host->mmc->supply.vmmc))
> > > > + mmc_regulator_set_ocr(host->mmc,
> > > > + host->mmc->supply.vmmc,
> > > > + ios->vdd);
> > > > + break;
> > > > + default:
> > > > + break;
> > > > + }
> > > > +
> > > > if (ios->clock)
> > > > mxs_ssp_set_clk_rate(&host->ssp, ios->clock);
> > > > }
> > > > @@ -588,7 +604,6 @@ static int mxs_mmc_probe(struct platform_device *pdev)
> > > > struct mmc_host *mmc;
> > > > struct resource *iores;
> > > > int ret = 0, irq_err;
> > > > - struct regulator *reg_vmmc;
> > > > struct mxs_ssp *ssp;
> > > >
> > > > irq_err = platform_get_irq(pdev, 0);
> > > > @@ -614,14 +629,15 @@ static int mxs_mmc_probe(struct platform_device *pdev)
> > > > host->mmc = mmc;
> > > > host->sdio_irq_en = 0;
> > > >
> > > > - reg_vmmc = devm_regulator_get(&pdev->dev, "vmmc");
> > > > - if (!IS_ERR(reg_vmmc)) {
> > > > - ret = regulator_enable(reg_vmmc);
> > > > - if (ret) {
> > > > - dev_err(&pdev->dev,
> > > > - "Failed to enable vmmc regulator: %d\n", ret);
> > > > - goto out_mmc_free;
> > > > - }
> > > > + ret = mmc_regulator_get_supply(mmc);
> > > > + if (ret == -EPROBE_DEFER)
> > > > + goto out_mmc_free;
> > > > +
> > > > + ret = regulator_enable(mmc->supply.vmmc);
> > >
> > > This is wrong, as it may cause the regulator usage count to become
> > > wrongly balanced.
> > >
> > > Instead, via ->set_ios() when calling mmc_regulator_set_ocr(), it will
> > > take care of enabling and disabling the regulator depending of the
> > > requested vdd voltage level.
> > >
> > > > + if (ret) {
> > > > + dev_err(&pdev->dev,
> > > > + "Failed to enable vmmc regulator: %d\n", ret);
> > > > + goto out_mmc_free;
> > > > }
> > > >
> > > > ssp->clk = devm_clk_get(&pdev->dev, NULL);
> > > > --
> > > > 2.20.1
> > > >
> > >
> > > BTW, you didn't really answer my earlier question about the TI WiFi
> > > chip. Doesn't you need a special clock for WiFi chip as well? How do
> > > you intend to manage that?
> >
> > I used an external 32K oscillator (SLOW_CLK) for my wl1271. Other
> > clocks ware generated on the module.
>
> Right. How do you control that clock? Did you model it as clock via
> the common clock framework?

No I didn't. The slow clock (sleep clock) was always 'on'.

>
> >
> > I had to supply a 'vmmc-supply' in your wl1271 devicetree node,
> > which will be used to power on/off the wlan module. The supply should
> > be a (delayed) GPIO controlled 'fixed-regulator' attached to the
> > wlan_en pin on the module.
>
> Right, thanks for explaining.
>
> >
> > 1: Documentation/devicetree/bindings/net/wireless/ti,wlcore.txt
> >
>
> This sounds like a good fit for mmc pwrseq simple. There are already
> similar users for it.
>
> Have a look at: /drivers/mmc/core/pwrseq*
> If the mmc host driver calls mmc_of_parse() during ->probe(), a pwrseq
> instance will be hooked up to it. Once the mmc core tries to power up
> the card it will make use of the attached pwrseq for the mmc host in
> question.
>
> In this way, you can control the clock and GPIO line, in more exact
> ways that is needed by the WiFi chip.

Ack. Makes more sense than using a regulator (even without specifying
'clocks').

>
> Here is a DT example (look for "mmc-pwrseq-simple"):
> arch/arm/boot/dts/imx6qdl-sr-som-ti.dtsi
>
> This should do the trick for you. On the other hand, I don't mind that
> you still add regulator support to the driver, along the lines of what
> $subject patch does, however it may not be exactly what you need for
> the WiFi case.

@Martin; What do you think? Will you work this out with Ulf?
Since I can't test this.

Regards,
Robin

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