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SubjectRe: [PATCH 13/40] mmc: tegra: Poll for calibration completion
On Thu, 9 Aug 2018 14:46:16 +0200
Thierry Reding <thierry.reding@gmail.com> wrote:

> On Wed, Aug 01, 2018 at 07:32:03PM +0300, Aapo Vienamo wrote:
> > Implement polling with 10 ms timeout for automatic pad drive strength
> > calibration.
> >
> > Signed-off-by: Aapo Vienamo <avienamo@nvidia.com>
> > ---
> > drivers/mmc/host/sdhci-tegra.c | 21 ++++++++++++++++-----
> > 1 file changed, 16 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
> > index 7d98455..c8ff267 100644
> > --- a/drivers/mmc/host/sdhci-tegra.c
> > +++ b/drivers/mmc/host/sdhci-tegra.c
> > @@ -16,6 +16,7 @@
> > #include <linux/err.h>
> > #include <linux/module.h>
> > #include <linux/init.h>
> > +#include <linux/iopoll.h>
> > #include <linux/platform_device.h>
> > #include <linux/clk.h>
> > #include <linux/io.h>
> > @@ -50,6 +51,9 @@
> > #define SDHCI_AUTO_CAL_START BIT(31)
> > #define SDHCI_AUTO_CAL_ENABLE BIT(29)
> >
> > +#define SDHCI_TEGRA_AUTO_CAL_STATUS 0x1ec
> > +#define SDHCI_TEGRA_AUTO_CAL_ACTIVE BIT(31)
> > +
> > #define NVQUIRK_FORCE_SDHCI_SPEC_200 BIT(0)
> > #define NVQUIRK_ENABLE_BLOCK_GAP_DET BIT(1)
> > #define NVQUIRK_ENABLE_SDHCI_SPEC_300 BIT(2)
> > @@ -228,13 +232,20 @@ static void tegra_sdhci_reset(struct sdhci_host *host, u8 mask)
> >
> > static void tegra_sdhci_pad_autocalib(struct sdhci_host *host)
> > {
> > - u32 val;
> > + u32 reg;
> > + int ret;
> > +
> > + reg = sdhci_readl(host, SDHCI_TEGRA_AUTO_CAL_CONFIG);
> > + reg |= SDHCI_AUTO_CAL_ENABLE | SDHCI_AUTO_CAL_START;
> > + sdhci_writel(host, reg, SDHCI_TEGRA_AUTO_CAL_CONFIG);
> >
>
> I know this is preexisting, but I want to make sure we cover this so we
> don't run into this down the road: do these bits automatically clear on
> calibration completion? Can we run these multiple times and get
> everything properly calibrated?

The TRM states in the pad auto-calibration procedure description that
this bit should not be cleared.

-Aapo

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