Date:   Wed, 10 Jan 2018 09:31:05 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     "ernest.zhang" <ernest.zhang@...hubtech.com>,
        ulf.hansson@...aro.org, linux-mmc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     yuxiang.wan@...hubtech.com, xiaoguang.yu@...hubtech.com,
        shirley.her@...hubtech.com, Craig Bergstrom <craigb@...gle.com>
Subject: Re: [PATCH 3/3] mmc: sdhci: fix o2 eMMC init bug and add support for
 hardware tuning

On 28/12/17 12:00, ernest.zhang wrote:
> In some case of eMMC used as boot device, the eMMC signaling voltage is
> fixed to 1.8v, bios can set o2 sd host controller register 0x308 bit4 to
> let host controller skip try 3.3.v signaling voltage in eMMC initialize
> process.
> O2 sd host controller has a function named hardware tuning. In software
> tuning mode CPU should send multiple command to host controller but in
> hardware tuning mode, CPU need send only one tuning command to sd host
> controller. It can improve the speed linux boot from eMMC.

Please put the changes from patch 2 into this patch, re-base, and put V3 on
the next submission.  Note the mmc tree is:

	git://git.kernel.org/pub/scm/linux/kernel/git/ulfh/mmc.git

Re-base on the 'next' branch.

Also Craig Bergstrom reported problems getting it to work, so please respond
to that, otherwise I am left wondering if this rather strange tuning
procedure actually works:

	https://marc.info/?l=linux-mmc&m=151387671202146&w=2

> 
> Signed-off-by: ernest.zhang <ernest.zhang@...hubtech.com>
> ---
>  drivers/mmc/host/sdhci-pci-o2micro.c | 218 ++++++++++++++++++++++++++++++++++-
>  1 file changed, 217 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mmc/host/sdhci-pci-o2micro.c b/drivers/mmc/host/sdhci-pci-o2micro.c
> index 14273ca00641..fd244d88b07e 100644
> --- a/drivers/mmc/host/sdhci-pci-o2micro.c
> +++ b/drivers/mmc/host/sdhci-pci-o2micro.c
> @@ -16,11 +16,211 @@
>   */
>  
>  #include <linux/pci.h>
> -
> +#include <linux/platform_device.h>
> +#include <linux/regulator/fixed.h>
> +#include <linux/regulator/machine.h>
> +#include <linux/mmc/host.h>
> +#include <linux/mmc/mmc.h>
> +#include <linux/delay.h>
>  #include "sdhci.h"
>  #include "sdhci-pci.h"
>  #include "sdhci-pci-o2micro.h"
>  
> +static void sdhci_o2_start_tuning(struct sdhci_host *host)
> +{
> +	u16 ctrl;
> +
> +	ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
> +	ctrl |= SDHCI_CTRL_EXEC_TUNING;
> +	if (host->quirks2 & SDHCI_QUIRK2_TUNING_WORK_AROUND)
> +		ctrl |= SDHCI_CTRL_TUNED_CLK;

Why program for a quirk that you don't use?

> +	sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
> +
> +	/*
> +	 * As per the Host Controller spec v3.00, tuning command
> +	 * generates Buffer Read Ready interrupt, so enable that.
> +	 *
> +	 * Note: The spec clearly says that when tuning sequence
> +	 * is being performed, the controller does not generate
> +	 * interrupts other than Buffer Read Ready interrupt. But
> +	 * to make sure we don't hit a controller bug, we _only_
> +	 * enable Buffer Read Ready interrupt here.
> +	 */
> +	sdhci_writel(host, SDHCI_INT_DATA_AVAIL, SDHCI_INT_ENABLE);
> +	sdhci_writel(host, SDHCI_INT_DATA_AVAIL, SDHCI_SIGNAL_ENABLE);
> +}
> +
> +static void sdhci_o2_end_tuning(struct sdhci_host *host)
> +{
> +	sdhci_writel(host, host->ier, SDHCI_INT_ENABLE);
> +	sdhci_writel(host, host->ier, SDHCI_SIGNAL_ENABLE);
> +}
> +
> +static inline bool sdhci_data_line_cmd(struct mmc_command *cmd)
> +{
> +	return cmd->data || cmd->flags & MMC_RSP_BUSY;
> +}
> +
> +static void sdhci_del_timer(struct sdhci_host *host, struct mmc_request *mrq)
> +{
> +	if (sdhci_data_line_cmd(mrq->cmd))
> +		del_timer(&host->data_timer);
> +	else
> +		del_timer(&host->timer);
> +}
> +
> +static void sdhci_o2_set_tuning_mode(struct sdhci_host *host, bool hw)

Since you only ever call this with hw = true, maybe drop the 'hw' parameter
altogether.

> +{
> +	u16 reg;
> +
> +	if (hw) {
> +		// enable hardware tuning

For consistency, please use old C-style comments /* */ instead of //

> +		reg = sdhci_readw(host, O2_SD_VENDOR_SETTING);
> +		reg &= (~O2_SD_HW_TUNING_ENABLE);
> +		sdhci_writew(host, reg, O2_SD_VENDOR_SETTING);
> +	} else {
> +		reg = sdhci_readw(host, O2_SD_VENDOR_SETTING);
> +		reg |= O2_SD_HW_TUNING_ENABLE;
> +		sdhci_writew(host, reg, O2_SD_VENDOR_SETTING);
> +	}
> +}
> +
> +static u8 data_buf[64];

It would be better to allocate data_buf.

> +
> +static void sdhci_o2_send_tuning(struct sdhci_host *host, u32 opcode)
> +{
> +	struct mmc_command cmd = { };
> +	struct mmc_data data = { };
> +	struct scatterlist sg;
> +	struct mmc_request mrq = { };
> +	unsigned long flags;
> +	u32 b = host->sdma_boundary;
> +	int size = sizeof(data_buf);
> +
> +	cmd.opcode = opcode;
> +	cmd.flags = MMC_RSP_PRESENT | MMC_RSP_OPCODE | MMC_RSP_CRC;
> +	cmd.mrq = &mrq;
> +	mrq.cmd = &cmd;
> +	mrq.data = &data;
> +	data.blksz = size;
> +	data.blocks = 1;
> +	data.flags = MMC_DATA_READ;
> +
> +	data.timeout_ns = 150 * NSEC_PER_MSEC;

It seems inconsistent to set 150ms timeout here but 50ms for waiting for
Buffer Read Ready.

> +
> +	data.sg = &sg;
> +	data.sg_len = 1;
> +	sg_init_one(&sg, data_buf, size);
> +
> +	spin_lock_irqsave(&host->lock, flags);
> +
> +	sdhci_writew(host, SDHCI_MAKE_BLKSZ(b, 64), SDHCI_BLOCK_SIZE);
> +
> +	/*
> +	 * The tuning block is sent by the card to the host controller.
> +	 * So we set the TRNS_READ bit in the Transfer Mode register.
> +	 * This also takes care of setting DMA Enable and Multi Block
> +	 * Select in the same register to 0.
> +	 */
> +	sdhci_writew(host, SDHCI_TRNS_READ, SDHCI_TRANSFER_MODE);

That won't work because the transfer mode gets overwritten by
sdhci_send_command().

> +
> +	sdhci_send_command(host, &cmd);
> +
> +	host->cmd = NULL;
> +
> +	sdhci_del_timer(host, &mrq);

Simpler would be:

	del_timer(&host->data_timer);

> +
> +	host->tuning_done = 0;
> +
> +	mmiowb();
> +	spin_unlock_irqrestore(&host->lock, flags);
> +
> +	/* Wait for Buffer Read Ready interrupt */
> +	wait_event_timeout(host->buf_ready_int, (host->tuning_done == 1),
> +			   msecs_to_jiffies(50));
> +
> +}
> +
> +static void sdhci_o2_reset_tuning(struct sdhci_host *host)
> +{
> +	u16 ctrl;
> +
> +	ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
> +	ctrl &= ~SDHCI_CTRL_TUNED_CLK;
> +	ctrl &= ~SDHCI_CTRL_EXEC_TUNING;
> +	sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
> +}
> +
> +static void __sdhci_o2_execute_tuning(struct sdhci_host *host, u32 opcode)
> +{
> +	int i;
> +
> +	sdhci_o2_send_tuning(host, MMC_SEND_TUNING_BLOCK_HS200);
> +
> +	for (i = 0; i < 150; i++) {
> +		u16 ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
> +
> +		if (!(ctrl & SDHCI_CTRL_EXEC_TUNING)) {
> +			if (ctrl & SDHCI_CTRL_TUNED_CLK) {
> +				pr_info("%s: HW tuning ok !\n",
> +					mmc_hostname(host->mmc));

This message does not look necessary.

> +				host->tuning_done = true;
> +				return;
> +			}
> +			pr_warn("%s: HW tuning failed !\n",
> +				   mmc_hostname(host->mmc));
> +			break;
> +		}
> +
> +		mdelay(1);

This could be msleep() or usleep_range()

> +	}
> +
> +	pr_info("%s: Tuning failed, falling back to fixed sampling clock\n",
> +		mmc_hostname(host->mmc));
> +	sdhci_o2_reset_tuning(host);
> +}
> +
> +static int sdhci_o2_execute_tuning(struct mmc_host *mmc, u32 opcode)
> +{
> +	struct sdhci_host *host = mmc_priv(mmc);
> +	int current_bus_width = 0;
> +
> +	/*
> +	 * This handler only implements the eMMC tuning that is specific to
> +	 * this controller.  Fall back to the standard method for other TINMING.

TINMING -> TIMING

> +	 */
> +	if (host->timing != MMC_TIMING_MMC_HS200)
> +		return sdhci_execute_tuning(mmc, opcode);
> +
> +	if (WARN_ON(opcode != MMC_SEND_TUNING_BLOCK_HS200))
> +		return -EINVAL;
> +
> +	/*
> +	 * o2 sdhci host didn't support 8bit emmc tuning
> +	 */
> +	if (mmc->ios.bus_width == MMC_BUS_WIDTH_8) {
> +		current_bus_width = mmc->ios.bus_width;
> +		mmc->ios.bus_width = MMC_BUS_WIDTH_4;
> +		mmc->ops->set_ios(mmc, &mmc->ios);

Using sdhci_set_bus_width() would be simpler.

> +	}
> +
> +	sdhci_o2_set_tuning_mode(host, true);
> +
> +	sdhci_o2_start_tuning(host);
> +
> +	__sdhci_o2_execute_tuning(host, opcode);
> +
> +	sdhci_o2_end_tuning(host);
> +
> +	if (current_bus_width == MMC_BUS_WIDTH_8) {
> +		mmc->ios.bus_width = current_bus_width;
> +		mmc->ops->set_ios(mmc, &mmc->ios);
> +	}
> +
> +	host->flags &= ~SDHCI_HS400_TUNING;
> +	return 0;
> +}
> +
>  static void o2_pci_set_baseclk(struct sdhci_pci_chip *chip, u32 value)
>  {
>  	u32 scratch_32;
> @@ -151,6 +351,7 @@ int sdhci_pci_o2_probe_slot(struct sdhci_pci_slot *slot)
>  	struct sdhci_pci_chip *chip;
>  	struct sdhci_host *host;
>  	u32 reg;
> +	int ret;
>  
>  	chip = slot->chip;
>  	host = slot->host;
> @@ -164,6 +365,21 @@ int sdhci_pci_o2_probe_slot(struct sdhci_pci_slot *slot)
>  		if (reg & 0x1)
>  			host->quirks |= SDHCI_QUIRK_MULTIBLOCK_READ_ACMD12;
>  
> +		if (chip->pdev->device == PCI_DEVICE_ID_O2_SEABIRD0) {
> +			ret = pci_read_config_dword(chip->pdev,
> +						    O2_SD_MISC_SETTING, &reg);
> +			if (ret)
> +				return -EIO;
> +			if (reg & (1 << 4)) {
> +				pr_info("%s: emmc 1.8v flag is set, force 1.8v signaling voltage\n",
> +				     mmc_hostname(host->mmc));
> +				host->flags &= ~(SDHCI_SIGNALING_330);

Parenthesis not needed.

> +				host->flags |= SDHCI_SIGNALING_180;
> +			}
> +		}
> +
> +		host->mmc_host_ops.execute_tuning = sdhci_o2_execute_tuning;
> +
>  		if (chip->pdev->device != PCI_DEVICE_ID_O2_FUJIN2)
>  			break;
>  		/* set dll watch dog timer */
> 

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