On Thu, Aug 09, 2018 at 03:56:38PM +0300, Aapo Vienamo wrote:

On Thu, 9 Aug 2018 14:46:16 +0200
Thierry Reding [off-list ref] wrote:

quoted

On Wed, Aug 01, 2018 at 07:32:03PM +0300, Aapo Vienamo wrote:

quoted

Implement polling with 10 ms timeout for automatic pad drive strength
calibration.

Signed-off-by: Aapo Vienamo <redacted>
---
 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.

It says that SDHCI_AUTO_CAL_ENABLE shouldn't be cleared after
calibration completes, but I'm wondering how recalibration is going to
happen on a second run.

I guess if we never turn off calibration, then it will continue to run
forever, but does that also work if we go back to a mode that doesn't
require calibration?

So perhaps what we need is to clear SDHCI_AUTO_CAL_ENABLE when going to
such a mode. And perhaps we need to clear SDHCI_AUTO_CAL_START after the
calibration is complete.

Anyway, lots of unanswered questions and if the above works, I'm fine
with merging it as-is. If we find out that something else is needed at a
later point we can always fix it up later.

Thierry