From: Maxime Ripard <maxime.ripard@free-electrons.com>
To: Chen-Yu Tsai <wens@csie.org>,
Maxime Ripard <maxime.ripard@free-electrons.com>,
Ulf Hansson <ulf.hansson@linaro.org>
Cc: Rob Herring <robh+dt@kernel.org>,
devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-mmc@vger.kernel.org,
Andre Przywara <andre.przywara@arm.com>
Subject: [PATCH v4 3/13] mmc: sunxi: Always set signal delay to 0 for A64
Date: Thu, 26 Jan 2017 10:05:56 +0100 [thread overview]
Message-ID: <6c9dae7e6c872420e5e565efb334be411269be21.1485421557.git-series.maxime.ripard@free-electrons.com> (raw)
In-Reply-To: <cover.8d42a39b7bd5143e709979dc42cc47862ebe3728.1485421557.git-series.maxime.ripard@free-electrons.com>
In-Reply-To: <cover.8d42a39b7bd5143e709979dc42cc47862ebe3728.1485421557.git-series.maxime.ripard@free-electrons.com>
Experience have shown that the using the autocalibration could severely
degrade the performances of the MMC bus.
Allwinner is using in its BSP a delay set to 0 for all the modes but HS400.
Remove the calibration code for now, and add comments to document our
findings.
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
---
drivers/mmc/host/sunxi-mmc.c | 50 ++++++++++++-------------------------
1 file changed, 17 insertions(+), 33 deletions(-)
diff --git a/drivers/mmc/host/sunxi-mmc.c b/drivers/mmc/host/sunxi-mmc.c
index 019f95e8e7c5..b9c8a62bc212 100644
--- a/drivers/mmc/host/sunxi-mmc.c
+++ b/drivers/mmc/host/sunxi-mmc.c
@@ -683,41 +683,19 @@ static int sunxi_mmc_oclk_onoff(struct sunxi_mmc_host *host, u32 oclk_en)
static int sunxi_mmc_calibrate(struct sunxi_mmc_host *host, int reg_off)
{
- u32 reg = readl(host->reg_base + reg_off);
- u32 delay;
- unsigned long timeout;
-
if (!host->cfg->can_calibrate)
return 0;
- reg &= ~(SDXC_CAL_DL_MASK << SDXC_CAL_DL_SW_SHIFT);
- reg &= ~SDXC_CAL_DL_SW_EN;
-
- writel(reg | SDXC_CAL_START, host->reg_base + reg_off);
-
- dev_dbg(mmc_dev(host->mmc), "calibration started\n");
-
- timeout = jiffies + HZ * SDXC_CAL_TIMEOUT;
-
- while (!((reg = readl(host->reg_base + reg_off)) & SDXC_CAL_DONE)) {
- if (time_before(jiffies, timeout))
- cpu_relax();
- else {
- reg &= ~SDXC_CAL_START;
- writel(reg, host->reg_base + reg_off);
-
- return -ETIMEDOUT;
- }
- }
-
- delay = (reg >> SDXC_CAL_DL_SHIFT) & SDXC_CAL_DL_MASK;
-
- reg &= ~SDXC_CAL_START;
- reg |= (delay << SDXC_CAL_DL_SW_SHIFT) | SDXC_CAL_DL_SW_EN;
-
- writel(reg, host->reg_base + reg_off);
-
- dev_dbg(mmc_dev(host->mmc), "calibration ended, reg is 0x%x\n", reg);
+ /*
+ * FIXME:
+ * This is not clear how the calibration is supposed to work
+ * yet. The best rate have been obtained by simply setting the
+ * delay to 0, as Allwinner does in its BSP.
+ *
+ * The only mode that doesn't have such a delay is HS400, that
+ * is in itself a TODO.
+ */
+ writel(SDXC_CAL_DL_SW_EN, host->reg_base + reg_off);
return 0;
}
@@ -809,7 +787,13 @@ static int sunxi_mmc_clk_set_rate(struct sunxi_mmc_host *host,
if (ret)
return ret;
- /* TODO: enable calibrate on sdc2 SDXC_REG_DS_DL_REG of A64 */
+ /*
+ * FIXME:
+ *
+ * In HS400 we'll also need to calibrate the data strobe
+ * signal. This should only happen on the MMC2 controller (at
+ * least on the A64).
+ */
return sunxi_mmc_oclk_onoff(host, 1);
}
--
git-series 0.8.11
next prev parent reply other threads:[~2017-01-26 9:09 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-26 9:05 [PATCH v4 0/13] arm64: allwinner: a64: Enable MMC support Maxime Ripard
2017-01-26 9:05 ` [PATCH v4 1/13] mmc: sunxi: Fix clock frequency change sequence Maxime Ripard
2017-01-26 9:05 ` [PATCH v4 2/13] mmc: sunxi: Gate the clock when rate is 0 Maxime Ripard
2017-01-26 9:05 ` Maxime Ripard [this message]
2017-01-26 9:05 ` [PATCH v4 4/13] mmc: sunxi: Enable the new timings for the A64 MMC controllers Maxime Ripard
2017-01-26 9:05 ` [PATCH v4 5/13] mmc: sunxi: Mask DATA0 when updating the clock Maxime Ripard
2017-01-26 9:05 ` [PATCH v4 6/13] mmc: sunxi: Add EMMC (MMC2) controller compatible Maxime Ripard
2017-01-26 9:06 ` [PATCH v4 7/13] mmc: sunxi: Add more debug informations Maxime Ripard
2017-01-26 9:06 ` [PATCH v4 8/13] arm64: allwinner: a64: Add MMC nodes Maxime Ripard
2017-01-26 9:06 ` [PATCH v4 9/13] arm64: allwinner: a64: Add MMC pinctrl nodes Maxime Ripard
2017-01-26 9:06 ` [PATCH v4 10/13] arm64: allwinner: a64: Increase the MMC max frequency Maxime Ripard
2017-01-27 10:29 ` Florian Vaussard
2017-01-27 21:26 ` Maxime Ripard
2017-01-26 9:06 ` [PATCH v4 11/13] arm64: allwinner: pine64: add MMC support Maxime Ripard
2017-01-26 9:06 ` [PATCH v4 12/13] arm64: allwinner: a64: add UART1 pin nodes Maxime Ripard
2017-01-26 9:06 ` [PATCH v4 13/13] arm64: allwinner: add BananaPi-M64 support Maxime Ripard
2017-01-27 10:37 ` [PATCH v4 0/13] arm64: allwinner: a64: Enable MMC support Florian Vaussard
2017-01-27 21:27 ` Maxime Ripard
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