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SubjectRe: [PATCH v4] mmc: mxs-mmc: Introduce regulator support
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.

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.

1: Documentation/devicetree/bindings/net/wireless/ti,wlcore.txt

Kind regards,

--
Robin van der Gracht
Protonic Holland
tel.: +31 (0) 229 212928
fax.: +31 (0) 229 210930
Factorij 36 / 1689 AL Zwaag

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