Re: [RFC] sdhci: 8 bit bus width changes

[Chris Ball <cjb@laptop.org>]

On Fri, Nov 19, 2010 at 09:40:02PM +0000, Chris Ball wrote:
> I don't see why we should re-read ctrl here, since we've already written
> it back to the device at this point, and we don't use it anywhere below
> this line.

Ah, I see why now; please ignore this. 

Here's a rebased version of the patch, with some more comments:

From: Philip Rakity <prakity@marvell.com>
Date: Fri, 19 Nov 2010 16:48:39 -0500
Subject: [PATCH] mmc: sdhci: 8-bit bus width changes

We now:
 * check for a v3 controller before setting 8-bit bus width
 * offer a callback for platform code to switch to 8-bit mode, which
   allows non-v3 controllers to support it
 * introduce a quirk to specify that the board designers have indeed
   brought out all the pins for 8-bit to the slot.

We were previously relying only on whether the controller supported
8-bit, which doesn't tell us anything about the pin configuration in
the board design.

Signed-off-by: Philip Rakity <prakity@marvell.com>
Tested-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: Chris Ball <cjb@laptop.org>
---
 drivers/mmc/host/sdhci.c  |   48 +++++++++++++++++++++++++++++++++-----------
 drivers/mmc/host/sdhci.h  |    5 +++-
 include/linux/mmc/sdhci.h |    2 +
 3 files changed, 42 insertions(+), 13 deletions(-)

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 154cbf8..f1f9658 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1185,17 +1185,31 @@ static void sdhci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
 	if (host->ops->platform_send_init_74_clocks)
 		host->ops->platform_send_init_74_clocks(host, ios->power_mode);
 
-	ctrl = sdhci_readb(host, SDHCI_HOST_CONTROL);
-
-	if (ios->bus_width == MMC_BUS_WIDTH_8)
-		ctrl |= SDHCI_CTRL_8BITBUS;
-	else
-		ctrl &= ~SDHCI_CTRL_8BITBUS;
+	/*
+	 * If your platform has 8-bit width support but is not a v3 controller,
+	 * or if it requires special setup code, you should implement that in
+	 * platform_8bit_width().
+	 */
+	if (host->ops->platform_8bit_width)
+		host->ops->platform_8bit_width(host, ios->bus_width);
+	else {
+		ctrl = sdhci_readb(host, SDHCI_HOST_CONTROL);
+		if (ios->bus_width == MMC_BUS_WIDTH_8) {
+			ctrl &= ~SDHCI_CTRL_4BITBUS;
+			if (host->version >= SDHCI_SPEC_300)
+				ctrl |= SDHCI_CTRL_8BITBUS;
+		} else {
+			if (host->version >= SDHCI_SPEC_300)
+				ctrl &= ~SDHCI_CTRL_8BITBUS;
+			if (ios->bus_width == MMC_BUS_WIDTH_4)
+				ctrl |= SDHCI_CTRL_4BITBUS;
+			else
+				ctrl &= ~SDHCI_CTRL_4BITBUS;
+		}
+		sdhci_writeb(host, ctrl, SDHCI_HOST_CONTROL);
+	}
 
-	if (ios->bus_width == MMC_BUS_WIDTH_4)
-		ctrl |= SDHCI_CTRL_4BITBUS;
-	else
-		ctrl &= ~SDHCI_CTRL_4BITBUS;
+	ctrl = sdhci_readb(host, SDHCI_HOST_CONTROL);
 
 	if ((ios->timing == MMC_TIMING_SD_HS ||
 	     ios->timing == MMC_TIMING_MMC_HS)
@@ -1855,11 +1869,21 @@ int sdhci_add_host(struct sdhci_host *host)
 		mmc->f_min = host->max_clk / SDHCI_MAX_DIV_SPEC_300;
 	else
 		mmc->f_min = host->max_clk / SDHCI_MAX_DIV_SPEC_200;
+
 	mmc->f_max = host->max_clk;
 	mmc->caps |= MMC_CAP_SDIO_IRQ;
 
-	if (!(host->quirks & SDHCI_QUIRK_FORCE_1_BIT_DATA))
-		mmc->caps |= MMC_CAP_4_BIT_DATA | MMC_CAP_8_BIT_DATA;
+	/*
+	 * A controller may support 8-bit width, but the board itself
+	 * might not have the pins brought out.  So, boards that support
+	 * 8-bit width should set the below quirk, and we won't assume
+	 * that devices without the quirk can use 8-bit width.
+	 */
+	if (!(host->quirks & SDHCI_QUIRK_FORCE_1_BIT_DATA)) {
+		mmc->caps |= MMC_CAP_4_BIT_DATA;
+		if (host->quirks & SDHCI_QUIRK_SLOT_CAN_DO_8_BITS)
+			mmc->caps |= MMC_CAP_8_BIT_DATA;
+	}
 
 	if (caps & SDHCI_CAN_DO_HISPD)
 		mmc->caps |= MMC_CAP_SD_HIGHSPEED | MMC_CAP_MMC_HIGHSPEED;
diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
index d52a716..e42d7f0 100644
--- a/drivers/mmc/host/sdhci.h
+++ b/drivers/mmc/host/sdhci.h
@@ -76,7 +76,7 @@
 #define   SDHCI_CTRL_ADMA1	0x08
 #define   SDHCI_CTRL_ADMA32	0x10
 #define   SDHCI_CTRL_ADMA64	0x18
-#define  SDHCI_CTRL_8BITBUS	0x20
+#define   SDHCI_CTRL_8BITBUS	0x20
 
 #define SDHCI_POWER_CONTROL	0x29
 #define  SDHCI_POWER_ON		0x01
@@ -155,6 +155,7 @@
 #define  SDHCI_CLOCK_BASE_SHIFT	8
 #define  SDHCI_MAX_BLOCK_MASK	0x00030000
 #define  SDHCI_MAX_BLOCK_SHIFT  16
+#define  SDHCI_CAN_DO_8BIT	0x00040000
 #define  SDHCI_CAN_DO_ADMA2	0x00080000
 #define  SDHCI_CAN_DO_ADMA1	0x00100000
 #define  SDHCI_CAN_DO_HISPD	0x00200000
@@ -215,6 +216,8 @@ struct sdhci_ops {
 	unsigned int	(*get_max_clock)(struct sdhci_host *host);
 	unsigned int	(*get_min_clock)(struct sdhci_host *host);
 	unsigned int	(*get_timeout_clock)(struct sdhci_host *host);
+	int		(*platform_8bit_width)(struct sdhci_host *host,
+					       int width);
 	void (*platform_send_init_74_clocks)(struct sdhci_host *host,
 					     u8 power_mode);
 	unsigned int    (*get_ro)(struct sdhci_host *host);
diff --git a/include/linux/mmc/sdhci.h b/include/linux/mmc/sdhci.h
index 1fdc673..7fdcfca 100644
--- a/include/linux/mmc/sdhci.h
+++ b/include/linux/mmc/sdhci.h
@@ -83,6 +83,8 @@ struct sdhci_host {
 #define SDHCI_QUIRK_MULTIBLOCK_READ_ACMD12		(1<<28)
 /* Controller doesn't have HISPD bit field in HI-SPEED SD card */
 #define SDHCI_QUIRK_NO_HISPD_BIT			(1<<29)
+/* Slot has 8 data pins going to eMMC/MMC card */
+#define SDHCI_QUIRK_SLOT_CAN_DO_8_BITS			(1<<30)
 
 	int irq;		/* Device IRQ */
 	void __iomem *ioaddr;	/* Mapped address */
-- 
Chris Ball   <cjb@laptop.org>   <http://printf.net/>
One Laptop Per Child