Re: [PATCH v4] mmc: mxs-mmc: Introduce regulator support

On Mon, 28 Jan 2019 22:15:23 +0100
Ulf Hansson [off-list ref] wrote:

On Mon, 28 Jan 2019 at 15:41, Martin Kepplinger [off-list ref] wrote:

quoted

From: Martin Kepplinger <redacted>

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 <redacted>
---


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.

quoted

+       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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