[PATCH 1/2] imx6-mmdc: Work around ERR050070

[John Watts]

The MPWLGCR registers clear the error bits before software can read them,
so rely on the MPWLHWERR registers for error reporting instead.

This errata was announced in 2019 and seems to apply to all chip revisions.

U-Boot contains a different workaround where it checks the calibration data
for the result 0x001F001F (maximum delay) and flag that as a failure.
This workaround seems to first publicly appear in the Novena U-Boot code
and originate from Freescale internal code or documentation.

While we're at it, fix the comment implying this code only checks PHY0 in x32
configuration. This is wrong and misleading.

Signed-off-by: John Watts <contact at jookia.org>
---
 arch/arm/mach-imx/imx6-mmdc.c              | 18 ++++++++++++++----
 arch/arm/mach-imx/include/mach/imx6-mmdc.h |  1 +
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/arch/arm/mach-imx/imx6-mmdc.c b/arch/arm/mach-imx/imx6-mmdc.c
index 00b8d30d69..908771626a 100644
--- a/arch/arm/mach-imx/imx6-mmdc.c
+++ b/arch/arm/mach-imx/imx6-mmdc.c
@@ -11,6 +11,18 @@
 #include <mach/imx6-regs.h>
 #include <mach/imx6.h>
 
+static bool wlcalib_failed(void __iomem *ips)
+{
+	int i;
+
+	for (i = 0; i < 4; ++i) {
+		if (readb(P0_IPS + MPWLHWERR + i) == 0)
+			return true;
+	}
+
+	return false;
+}
+
 int mmdc_do_write_level_calibration(void)
 {
 	u32 esdmisc_val, zq_val;
@@ -56,11 +68,9 @@ int mmdc_do_write_level_calibration(void)
 	/* Upon completion of this process the MMDC de-asserts the MPWLGCR[HW_WL_EN] */
 	while (readl(P0_IPS + MPWLGCR) & 0x00000001);
 
-	/* check for any errors: check both PHYs for x64 configuration, if x32, check only PHY0 */
-	if ((readl(P0_IPS + MPWLGCR) & 0x00000F00) ||
-			(readl(P1_IPS + MPWLGCR) & 0x00000F00)) {
+	/* check for any errors on both PHYs */
+	if (wlcalib_failed(P0_IPS) || wlcalib_failed(P1_IPS))
 		errorcount++;
-	}
 
 	pr_debug("Write leveling calibration completed\n");
 
diff --git a/arch/arm/mach-imx/include/mach/imx6-mmdc.h b/arch/arm/mach-imx/include/mach/imx6-mmdc.h
index bda20aba17..098ba4f5bf 100644
--- a/arch/arm/mach-imx/include/mach/imx6-mmdc.h
+++ b/arch/arm/mach-imx/include/mach/imx6-mmdc.h
@@ -18,6 +18,7 @@
 #define MPWLGCR		0x808
 #define MPWLDECTRL0	0x80c
 #define MPWLDECTRL1	0x810
+#define MPWLHWERR	0x878
 #define MPPDCMPR1	0x88c
 #define MPSWDAR		0x894
 #define MPRDDLCTL	0x848
-- 
2.39.0