Thread (27 messages) 27 messages, 3 authors, 2018-08-09

Re: [PATCH 2/8] mmc: tegra: Parse and program DQS trim value

From: Thierry Reding <hidden>
Date: 2018-08-09 11:40:52
Also in: linux-mmc, linux-tegra, lkml

On Tue, Aug 07, 2018 at 04:59:58PM +0300, Aapo Vienamo wrote:
quoted hunk ↗ jump to hunk
Parse and program the HS400 DQS trim value from dt. Program a fallback
value in case the property is missing.

Signed-off-by: Aapo Vienamo <redacted>
---
 drivers/mmc/host/sdhci-tegra.c | 32 +++++++++++++++++++++++++++++---
 1 file changed, 29 insertions(+), 3 deletions(-)
diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
index 7f1ac4a..426f7ea 100644
--- a/drivers/mmc/host/sdhci-tegra.c
+++ b/drivers/mmc/host/sdhci-tegra.c
@@ -43,6 +43,10 @@
 #define SDHCI_CLOCK_CTRL_PADPIPE_CLKEN_OVERRIDE		BIT(3)
 #define SDHCI_CLOCK_CTRL_SPI_MODE_CLKEN_OVERRIDE	BIT(2)
 
+#define SDHCI_TEGRA_VENDOR_CAP_OVERRIDES		0x10c
+#define SDHCI_TEGRA_CAP_OVERRIDES_DQS_TRIM_MASK		0x00003f00
+#define SDHCI_TEGRA_CAP_OVERRIDES_DQS_TRIM_SHIFT	8
+
 #define SDHCI_TEGRA_VENDOR_MISC_CTRL			0x120
 #define SDHCI_MISC_CTRL_ENABLE_SDR104			0x8
 #define SDHCI_MISC_CTRL_ENABLE_SDR50			0x10
@@ -112,6 +116,7 @@ struct sdhci_tegra {
 
 	u32 default_tap;
 	u32 default_trim;
+	u32 dqs_trim;
 };
 
 static u16 tegra_sdhci_readw(struct sdhci_host *host, int reg)
@@ -500,7 +505,7 @@ static void tegra_sdhci_parse_pad_autocal_dt(struct sdhci_host *host)
 		autocal->pull_down_hs400 = autocal->pull_down_1v8;
 }
 
-static void tegra_sdhci_parse_default_tap_and_trim(struct sdhci_host *host)
+static void tegra_sdhci_parse_tap_and_trim(struct sdhci_host *host)
 {
 	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
 	struct sdhci_tegra *tegra_host = sdhci_pltfm_priv(pltfm_host);
@@ -515,6 +520,11 @@ static void tegra_sdhci_parse_default_tap_and_trim(struct sdhci_host *host)
 				       &tegra_host->default_trim);
 	if (err)
 		tegra_host->default_trim = 0;
+
+	err = device_property_read_u32(host->mmc->parent, "nvidia,dqs-trim",
+				       &tegra_host->dqs_trim);
+	if (err)
+		tegra_host->dqs_trim = 0x11;
Okay, so there's only one value. I think that should be clarified in the
bindings documentation. It should mention that a single cell is used for
this. Also, I assume there are lower and upper limits for the valid
range of DQS trim values. Might make sense to specify those in the DT
bindings as well.
quoted hunk ↗ jump to hunk
 }
 
 static void tegra_sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
@@ -545,20 +555,33 @@ static unsigned int tegra_sdhci_get_max_clock(struct sdhci_host *host)
 	return clk_round_rate(pltfm_host->clk, UINT_MAX);
 }
 
+static void tegra_sdhci_set_dqs_trim(struct sdhci_host *host, u8 val)
+{
+	u32 reg;
+
+	reg = sdhci_readl(host, SDHCI_TEGRA_VENDOR_CAP_OVERRIDES);
+	reg &= ~SDHCI_TEGRA_CAP_OVERRIDES_DQS_TRIM_MASK;
+	reg |= val<<SDHCI_TEGRA_CAP_OVERRIDES_DQS_TRIM_SHIFT;
+	sdhci_writel(host, reg, SDHCI_TEGRA_VENDOR_CAP_OVERRIDES);
+}
Nit: I dislike using "reg" as a variable representing a register value
because I keep interpreting it as designating a register offset. Hence
I tend to use more explicit "offset" for actual register offsets and
"value" for register values.

But maybe that's just me.

Thierry

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