| Message ID | 20200419053746.22443-1-marek.behun@nic.cz (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mmc: sdhci-xenon: fix annoying 1.8V regulator warning | expand |
On Sun, 19 Apr 2020 07:37:46 +0200 Marek Behún <marek.behun@nic.cz> wrote: > For some reason the Host Control2 register of the Xenon SDHCI controller > sometimes reports the bit representing 1.8V signaling as 0 when read > after it was written as 1. Subsequent read reports 1. > > This causes the sdhci_start_signal_voltage_switch function to report > 1.8V regulator output did not become stable > > When CONFIG_PM is enabled, the host is suspended and resumend many > times, and in each resume the switch to 1.8V is called, and so the > kernel log reports this message annoyingly often. > > Do an empty read of the Host Control2 register in Xenon's > .voltage_switch method to circumvent this. > > Signed-off-by: Marek Behún <marek.behun@nic.cz> I should probably add a Fixes tag here so that it gets backported to stable versions. BTW this happens on Turris Mox.
On Mon, 20 Apr 2020 at 07:57, Marek Behun <marek.behun@nic.cz> wrote: > > On Sun, 19 Apr 2020 07:37:46 +0200 > Marek Behún <marek.behun@nic.cz> wrote: > > > For some reason the Host Control2 register of the Xenon SDHCI controller > > sometimes reports the bit representing 1.8V signaling as 0 when read > > after it was written as 1. Subsequent read reports 1. > > > > This causes the sdhci_start_signal_voltage_switch function to report > > 1.8V regulator output did not become stable > > > > When CONFIG_PM is enabled, the host is suspended and resumend many > > times, and in each resume the switch to 1.8V is called, and so the > > kernel log reports this message annoyingly often. > > > > Do an empty read of the Host Control2 register in Xenon's > > .voltage_switch method to circumvent this. > > > > Signed-off-by: Marek Behún <marek.behun@nic.cz> > > I should probably add a Fixes tag here so that it gets backported to > stable versions. Yes, please do. In regards to the comment in the code you added in $subject patch, I would suggest to slim down that quite a bit. More details are available in the commit message, so a few lines should be sufficient, in my opinion. > BTW this happens on Turris Mox. Perhaps add that in the commit message, too. Kind regards Uffe
diff --git a/drivers/mmc/host/sdhci-xenon.c b/drivers/mmc/host/sdhci-xenon.c index 1dea1ba66f7b..126ae723f8ab 100644 --- a/drivers/mmc/host/sdhci-xenon.c +++ b/drivers/mmc/host/sdhci-xenon.c @@ -235,6 +235,25 @@ static void xenon_voltage_switch(struct sdhci_host *host) { /* Wait for 5ms after set 1.8V signal enable bit */ usleep_range(5000, 5500); + + /* + * For some reason the controller's Host Control2 register reports + * the bit representing 1.8V signaling as 0 when read after it was + * written as 1. Subsequent read reports 1. + * + * This causes the sdhci_start_signal_voltage_switch function to + * report + * "1.8V regulator output did not become stable" + * in kernel log. + * + * When CONFIG_PM is enabled, the host is suspended and resumend many + * times, and in each resume the switch to 1.8V is called, and so the + * kernel log reports this message annoyingly often. + * + * Do an empty read of the Host Control2 register here to circumvent + * this. + */ + sdhci_readw(host, SDHCI_HOST_CONTROL2); } static const struct sdhci_ops sdhci_xenon_ops = {
For some reason the Host Control2 register of the Xenon SDHCI controller sometimes reports the bit representing 1.8V signaling as 0 when read after it was written as 1. Subsequent read reports 1. This causes the sdhci_start_signal_voltage_switch function to report 1.8V regulator output did not become stable When CONFIG_PM is enabled, the host is suspended and resumend many times, and in each resume the switch to 1.8V is called, and so the kernel log reports this message annoyingly often. Do an empty read of the Host Control2 register in Xenon's .voltage_switch method to circumvent this. Signed-off-by: Marek Behún <marek.behun@nic.cz> Cc: Zhoujie Wu <zjwu@marvell.com> Cc: Ulf Hansson <ulf.hansson@linaro.org> Cc: Gregory CLEMENT <gregory.clement@free-electrons.com> Cc: Vladimir Oltean <vladimir.oltean@nxp.com> --- drivers/mmc/host/sdhci-xenon.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)