Message-ID: <2eb54d36-0aea-fa80-4d13-9f92432da321@intel.com>
Date:   Wed, 18 Jul 2018 10:47:55 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Chunyan Zhang <zhang.lyra@...il.com>
Cc:     Chunyan Zhang <zhang.chunyan@...aro.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        linux-mmc@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Orson Zhai <orsonzhai@...il.com>,
        Baolin Wang <baolin.wang@...aro.org>,
        Billows Wu <billows.wu@...eadtrum.com>
Subject: Re: [PATCH V3 6/7] mmc: sdhci-sprd: added Spreadtrum's initial host
 controller

On 18/07/18 10:24, Chunyan Zhang wrote:
> On 17 July 2018 at 19:52, Adrian Hunter <adrian.hunter@...el.com> wrote:
>> On 09/07/18 06:19, Chunyan Zhang wrote:
>>> From: Chunyan Zhang <chunyan.zhang@...eadtrum.com>
>>>
>>> This patch adds the initial support of Secure Digital Host Controller
>>> Interface compliant controller found in some latest Spreadtrum chipsets.
>>> This patch has been tested on the version of SPRD-R11 controller.
>>>
>>> R11 is a variant based on SD v4.0 specification.
>>>
>>> With this driver, R11 mmc can be initialized, can be mounted, read and
>>> written.
>>>
>>> Original-by: Billows Wu <billows.wu@...eadtrum.com>
>>> Signed-off-by: Chunyan Zhang <chunyan.zhang@...eadtrum.com>
>>> ---
>>>  drivers/mmc/host/Kconfig      |  13 ++
>>>  drivers/mmc/host/Makefile     |   1 +
>>>  drivers/mmc/host/sdhci-sprd.c | 437 ++++++++++++++++++++++++++++++++++++++++++
>>>  3 files changed, 451 insertions(+)
>>>  create mode 100644 drivers/mmc/host/sdhci-sprd.c
>>>
>>> diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig
>>> index 0581c19..c5424dc 100644
>>> --- a/drivers/mmc/host/Kconfig
>>> +++ b/drivers/mmc/host/Kconfig
>>> @@ -581,6 +581,19 @@ config MMC_SDRICOH_CS
>>>         To compile this driver as a module, choose M here: the
>>>         module will be called sdricoh_cs.
>>>
>>> +config MMC_SDHCI_SPRD
>>> +     tristate "Spreadtrum SDIO host Controller"
>>> +     depends on ARCH_SPRD
>>> +     depends on MMC_SDHCI_PLTFM
>>> +     select MMC_SDHCI_IO_ACCESSORS
>>> +     help
>>> +       This selects the SDIO Host Controller in Spreadtrum
>>> +       SoCs, this driver supports R11(IP version: R11P0).
>>> +
>>> +       If you have a controller with this interface, say Y or M here.
>>> +
>>> +       If unsure, say N.
>>> +
>>>  config MMC_TMIO_CORE
>>>       tristate
>>>
>>> diff --git a/drivers/mmc/host/Makefile b/drivers/mmc/host/Makefile
>>> index 85dc132..b0b6802 100644
>>> --- a/drivers/mmc/host/Makefile
>>> +++ b/drivers/mmc/host/Makefile
>>> @@ -89,6 +89,7 @@ obj-$(CONFIG_MMC_SDHCI_ST)          += sdhci-st.o
>>>  obj-$(CONFIG_MMC_SDHCI_MICROCHIP_PIC32)      += sdhci-pic32.o
>>>  obj-$(CONFIG_MMC_SDHCI_BRCMSTB)              += sdhci-brcmstb.o
>>>  obj-$(CONFIG_MMC_SDHCI_OMAP)         += sdhci-omap.o
>>> +obj-$(CONFIG_MMC_SDHCI_SPRD)         += sdhci-sprd.o
>>>  obj-$(CONFIG_MMC_CQHCI)                      += cqhci.o
>>>
>>>  ifeq ($(CONFIG_CB710_DEBUG),y)
>>> diff --git a/drivers/mmc/host/sdhci-sprd.c b/drivers/mmc/host/sdhci-sprd.c
>>> new file mode 100644
>>> index 0000000..8d37ecb
>>> --- /dev/null
>>> +++ b/drivers/mmc/host/sdhci-sprd.c
>>> @@ -0,0 +1,437 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +//
>>> +// Secure Digital Host Controller
>>> +//
>>> +// Copyright (C) 2018 Spreadtrum, Inc.
>>> +// Author: Chunyan Zhang <chunyan.zhang@...eadtrum.com>
>>> +
>>> +#include <linux/delay.h>
>>> +#include <linux/dma-mapping.h>
>>> +#include <linux/highmem.h>
>>> +#include <linux/module.h>
>>> +#include <linux/of.h>
>>> +#include <linux/of_device.h>
>>> +#include <linux/of_gpio.h>
>>> +#include <linux/platform_device.h>
>>> +#include <linux/pm_runtime.h>
>>> +#include <linux/regulator/consumer.h>
>>> +#include <linux/slab.h>
>>> +
>>> +#include "sdhci-pltfm.h"
>>> +
>>> +#define SDHCI_SPRD_REG_32_DLL_DLY_OFFSET     0x208
>>> +#define  SDHCIBSPRD_IT_WR_DLY_INV            BIT(5)
>>> +#define  SDHCI_SPRD_BIT_CMD_DLY_INV          BIT(13)
>>> +#define  SDHCI_SPRD_BIT_POSRD_DLY_INV                BIT(21)
>>> +#define  SDHCI_SPRD_BIT_NEGRD_DLY_INV                BIT(29)
>>> +
>>> +#define SDHCI_SPRD_REG_32_BUSY_POSI          0x250
>>> +#define  SDHCI_SPRD_BIT_OUTR_CLK_AUTO_EN     BIT(25)
>>> +#define  SDHCI_SPRD_BIT_INNR_CLK_AUTO_EN     BIT(24)
>>> +
>>> +#define SDHCI_SPRD_REG_DEBOUNCE              0x28C
>>> +#define  SDHCI_SPRD_BIT_DLL_BAK              BIT(0)
>>> +#define  SDHCI_SPRD_BIT_DLL_VAL              BIT(1)
>>> +
>>> +#define  SDHCI_SPRD_INT_SIGNAL_MASK  0x1B7F410B
>>> +
>>> +/* SDHCI_HOST_CONTROL2 */
>>> +#define  SDHCI_SPRD_CTRL_HS200               0x0005
>>> +#define  SDHCI_SPRD_CTRL_HS400               0x0006
>>> +
>>> +/* SDHCI_SOFTWARE_RESET */
>>> +#define  SDHCI_HW_RESET_CARD         0x8 /* For Spreadtrum's design */
>>> +
>>> +#define SDHCI_SPRD_MAX_CUR           0xFFFFFF
>>> +#define SDHCI_SPRD_CLK_MAX_DIV               1023
>>> +
>>> +#define SDHCI_SPRD_CLK_DEF_RATE              26000000
>>> +
>>> +struct sdhci_sprd_host {
>>> +     u32 version;
>>> +     struct clk *clk_sdio;
>>> +     struct clk *clk_enable;
>>> +     u32 base_rate;
>>> +};
>>> +
>>> +#define TO_SPRD_HOST(host) sdhci_pltfm_priv(sdhci_priv(host))
>>> +
>>> +static void sdhci_sprd_init_config(struct sdhci_host *host)
>>> +{
>>> +     u16 val;
>>> +
>>> +     /* set 64-bit addressing modes */
>>> +     val = sdhci_readw(host, SDHCI_HOST_CONTROL2);
>>> +     val |= SDHCI_CTRL_64BIT_ADDR;
>>> +     sdhci_writew(host, val, SDHCI_HOST_CONTROL2);
>>
>> SDHCI should do that when enabling 64-bit DMA in V4 mode.  Needs to be done
>> either in sdhci_prepare_data() or after every reset or resume (e.g. when
>> ->enable_dma() is called).
> 
> Ok, then how about doing in sdhci_do_reset() once reset-for-all? That
> also can avoid to set this register each time when sending cmd if
> doing in sdhci_prepare_data().
> 
> I also prefer to move writing of SDHCI_HOST_CONTROL from
> sdhci_prepare_data() to sdhci_do_reset(), can that work properly?
> Since I noticed that flags of DMA (ADMA/SDMA) were set during
> initialization (i.e. probe).
> 
> What's your opinion?

Actually, looking at the code now, it looks like sdhci_init() is a better
place than sdhci_do_reset().

> 
>>
>>> +
>>> +     /* set dll backup mode */
>>> +     val = sdhci_readl(host, SDHCI_SPRD_REG_DEBOUNCE);
>>> +     val |= SDHCI_SPRD_BIT_DLL_BAK | SDHCI_SPRD_BIT_DLL_VAL;
>>> +     sdhci_writel(host, val, SDHCI_SPRD_REG_DEBOUNCE);
>>> +
>>> +     /* set CMD23 enabled */
>>> +     val = sdhci_readw(host, SDHCI_HOST_CONTROL2);
>>> +     val |= SDHCI_CMD23_ENABLE;
>>> +     sdhci_writew(host, val, SDHCI_HOST_CONTROL2);
>>
>> SDHCI should do that.  Needs to be done either when enabling auto-CMD23 or
>> after every reset or resume.
> 
> Ok, will do in sdhci_do_reset() as well.

That one is tricky since it needs to be based on the capability of the card.
 But again the setting can be done in sdhci_init().

> 
>>
>>> +}
>>> +
>>> +static inline u32 sdhci_sprd_readl(struct sdhci_host *host, int reg)
>>> +{
>>> +     if (unlikely(reg == SDHCI_MAX_CURRENT))
>>> +             return SDHCI_SPRD_MAX_CUR;
>>> +
>>> +     return readl_relaxed(host->ioaddr + reg);
>>> +}
>>> +
>>> +static inline void sdhci_sprd_writel(struct sdhci_host *host, u32 val, int reg)
>>> +{
>>> +     /* SDHCI_MAX_CURRENT is reserved on Spreadtrum's platform */
>>> +     if (unlikely(reg == SDHCI_MAX_CURRENT))
>>> +             return;
>>> +
>>> +     if (unlikely(reg == SDHCI_SIGNAL_ENABLE || reg == SDHCI_INT_ENABLE))
>>> +             val = val & SDHCI_SPRD_INT_SIGNAL_MASK;
>>> +
>>> +     writel_relaxed(val, host->ioaddr + reg);
>>> +}
>>> +
>>> +static inline void sdhci_sprd_writeb(struct sdhci_host *host, u8 val, int reg)
>>> +{
>>> +     if (unlikely(reg == SDHCI_SOFTWARE_RESET)) {
>>> +             if (readb_relaxed(host->ioaddr + reg) & SDHCI_HW_RESET_CARD)
>>> +                     val |= SDHCI_HW_RESET_CARD;
>>> +     }
>>> +
>>> +     writeb_relaxed(val, host->ioaddr + reg);
>>> +}
>>> +
>>> +static inline void sdhci_sprd_sd_clk_off(struct sdhci_host *host)
>>> +{
>>> +     u16 ctrl = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
>>> +
>>> +     ctrl &= ~SDHCI_CLOCK_CARD_EN;
>>> +     sdhci_writew(host, ctrl, SDHCI_CLOCK_CONTROL);
>>> +}
>>> +
>>> +static inline void
>>> +sdhci_sprd_set_dll_invert(struct sdhci_host *host, u32 mask, bool en)
>>> +{
>>> +     u32 dll_dly_offset;
>>> +
>>> +     dll_dly_offset = sdhci_readl(host, SDHCI_SPRD_REG_32_DLL_DLY_OFFSET);
>>> +     if (en)
>>> +             dll_dly_offset |= mask;
>>> +     else
>>> +             dll_dly_offset &= ~mask;
>>> +     sdhci_writel(host, dll_dly_offset, SDHCI_SPRD_REG_32_DLL_DLY_OFFSET);
>>> +}
>>> +
>>> +static inline u32 sdhci_sprd_calc_div(u32 base_clk, u32 clk)
>>> +{
>>> +     u32 div;
>>> +
>>> +     /* select 2x clock source */
>>> +     if (base_clk <= clk * 2)
>>> +             return 0;
>>> +
>>> +     div = (u32) (base_clk / (clk * 2));
>>> +
>>> +     if ((base_clk / div) > (clk * 2))
>>> +             div++;
>>> +
>>> +     if (div > SDHCI_SPRD_CLK_MAX_DIV)
>>> +             div = SDHCI_SPRD_CLK_MAX_DIV;
>>> +
>>> +     if (div % 2)
>>> +             div = (div + 1) / 2;
>>> +     else
>>> +             div = div / 2;
>>> +
>>> +     return div;
>>> +}
>>> +
>>> +static inline void _sdhci_sprd_set_clock(struct sdhci_host *host,
>>> +                                     unsigned int clk)
>>> +{
>>> +     struct sdhci_sprd_host *sprd_host = TO_SPRD_HOST(host);
>>> +     u32 div, val, mask;
>>> +
>>> +     div = sdhci_sprd_calc_div(sprd_host->base_rate, clk);
>>> +
>>> +     clk |= ((div & 0x300) >> 2) | ((div & 0xFF) << 8);
>>> +     sdhci_enable_clk(host, clk);
>>> +
>>> +     /* enable auto gate sdhc_enable_auto_gate */
>>> +     val = sdhci_readl(host, SDHCI_SPRD_REG_32_BUSY_POSI);
>>> +     mask = SDHCI_SPRD_BIT_OUTR_CLK_AUTO_EN |
>>> +            SDHCI_SPRD_BIT_INNR_CLK_AUTO_EN;
>>> +     if (mask != (val & mask)) {
>>> +             val |= mask;
>>> +             sdhci_writel(host, val, SDHCI_SPRD_REG_32_BUSY_POSI);
>>> +     }
>>> +}
>>> +
>>> +static void sdhci_sprd_set_clock(struct sdhci_host *host, unsigned int clock)
>>> +{
>>> +     bool en = false;
>>> +
>>> +     if (clock == 0) {
>>> +             sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
>>> +     } else if (clock != host->clock) {
>>> +             sdhci_sprd_sd_clk_off(host);
>>> +             _sdhci_sprd_set_clock(host, clock);
>>> +
>>> +             if (clock <= 400000)
>>> +                     en = true;
>>> +             sdhci_sprd_set_dll_invert(host, SDHCI_SPRD_BIT_CMD_DLY_INV |
>>> +                                       SDHCI_SPRD_BIT_POSRD_DLY_INV, en);
>>> +     } else {
>>> +             _sdhci_sprd_set_clock(host, clock);
>>> +     }
>>> +}
>>> +
>>> +static unsigned int sdhci_sprd_get_max_clock(struct sdhci_host *host)
>>> +{
>>> +     struct sdhci_sprd_host *sprd_host = TO_SPRD_HOST(host);
>>> +
>>> +     return clk_round_rate(sprd_host->clk_sdio, ULONG_MAX);
>>> +}
>>> +
>>> +static unsigned int sdhci_sprd_get_min_clock(struct sdhci_host *host)
>>> +{
>>> +     return 400000;
>>> +}
>>> +
>>> +static void sdhci_sprd_set_uhs_signaling(struct sdhci_host *host,
>>> +                                      unsigned int timing)
>>> +{
>>> +     u16 ctrl_2;
>>> +
>>> +     if (timing == host->timing)
>>> +             return;
>>> +
>>> +     ctrl_2 = sdhci_readw(host, SDHCI_HOST_CONTROL2);
>>> +     /* Select Bus Speed Mode for host */
>>> +     ctrl_2 &= ~SDHCI_CTRL_UHS_MASK;
>>> +     switch (timing) {
>>> +     case MMC_TIMING_UHS_SDR12:
>>> +             ctrl_2 = SDHCI_CTRL_UHS_SDR12;
>>
>> Shouldn't this and the following ones be '|=' not '='
>>
>>> +             break;
>>> +     case MMC_TIMING_MMC_HS:
>>> +     case MMC_TIMING_SD_HS:
>>> +     case MMC_TIMING_UHS_SDR25:
>>> +             ctrl_2 = SDHCI_CTRL_UHS_SDR25;
>>> +             break;
>>> +     case MMC_TIMING_UHS_SDR50:
>>> +             ctrl_2 = SDHCI_CTRL_UHS_SDR50;
>>> +             break;
>>> +     case MMC_TIMING_UHS_SDR104:
>>> +             ctrl_2 = SDHCI_CTRL_UHS_SDR104;
>>> +             break;
>>> +     case MMC_TIMING_UHS_DDR50:
>>> +     case MMC_TIMING_MMC_DDR52:
>>> +             ctrl_2 = SDHCI_CTRL_UHS_DDR50;
>>> +             break;
>>> +     case MMC_TIMING_MMC_HS200:
>>> +             ctrl_2 = SDHCI_SPRD_CTRL_HS200;
>>> +             break;
>>> +     case MMC_TIMING_MMC_HS400:
>>> +             ctrl_2 = SDHCI_SPRD_CTRL_HS400;
>>> +             break;
>>> +     default:
>>> +             break;
>>> +     }
>>> +
>>> +     sdhci_writew(host, ctrl_2, SDHCI_HOST_CONTROL2);
>>> +}
>>> +
>>> +static void sdhci_sprd_hw_reset(struct sdhci_host *host)
>>> +{
>>> +     int val;
>>> +
>>> +     /* Note: don't use sdhci_readb/writeb() API here */
>>> +     val = readb_relaxed(host->ioaddr + SDHCI_SOFTWARE_RESET);
>>> +     val &= ~SDHCI_HW_RESET_CARD;
>>> +     writeb_relaxed(val, host->ioaddr + SDHCI_SOFTWARE_RESET);
>>> +     udelay(10);
>>> +
>>> +     val |= SDHCI_HW_RESET_CARD;
>>> +     writeb_relaxed(val, host->ioaddr + SDHCI_SOFTWARE_RESET);
>>> +     udelay(300);
>>
>> usleep_range() maybe
> 
> Ok, I will have another look at it.
> 
> Thanks for the comments,
> Chunyan
> 
>>
>>> +}
>>> +
>>> +static struct sdhci_ops sdhci_sprd_ops = {
>>> +     .read_l = sdhci_sprd_readl,
>>> +     .write_l = sdhci_sprd_writel,
>>> +     .write_b = sdhci_sprd_writeb,
>>> +     .set_clock = sdhci_sprd_set_clock,
>>> +     .get_max_clock = sdhci_sprd_get_max_clock,
>>> +     .get_min_clock = sdhci_sprd_get_min_clock,
>>> +     .set_bus_width = sdhci_set_bus_width,
>>> +     .reset = sdhci_reset,
>>> +     .set_uhs_signaling = sdhci_sprd_set_uhs_signaling,
>>> +     .hw_reset = sdhci_sprd_hw_reset,
>>> +};
>>> +
>>> +static const struct sdhci_pltfm_data sdhci_sprd_pdata = {
>>> +     .quirks = SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK,
>>> +     .quirks2 = SDHCI_QUIRK2_BROKEN_HS200,
>>> +     .ops = &sdhci_sprd_ops,
>>> +};
>>> +
>>> +static int sdhci_sprd_probe(struct platform_device *pdev)
>>> +{
>>> +     struct sdhci_host *host;
>>> +     struct sdhci_sprd_host *sprd_host;
>>> +     struct clk *clk;
>>> +     int ret = 0;
>>> +
>>> +     host = sdhci_pltfm_init(pdev, &sdhci_sprd_pdata, sizeof(*sprd_host));
>>> +     if (IS_ERR(host))
>>> +             return PTR_ERR(host);
>>> +
>>> +     host->dma_mask = DMA_BIT_MASK(64);
>>> +     pdev->dev.dma_mask = &host->dma_mask;
>>> +
>>> +     host->mmc->caps = MMC_CAP_SD_HIGHSPEED | MMC_CAP_MMC_HIGHSPEED |
>>> +             MMC_CAP_ERASE | MMC_CAP_CMD23;
>>> +     ret = mmc_of_parse(host->mmc);
>>> +     if (ret)
>>> +             goto pltfm_free;
>>> +
>>> +     sprd_host = TO_SPRD_HOST(host);
>>> +
>>> +     clk = devm_clk_get(&pdev->dev, "sdio");
>>> +     if (IS_ERR(clk)) {
>>> +             ret = PTR_ERR(clk);
>>> +             goto pltfm_free;
>>> +     }
>>> +     sprd_host->clk_sdio = clk;
>>> +     sprd_host->base_rate = clk_get_rate(sprd_host->clk_sdio);
>>> +     if (!sprd_host->base_rate)
>>> +             sprd_host->base_rate = SDHCI_SPRD_CLK_DEF_RATE;
>>> +
>>> +     clk = devm_clk_get(&pdev->dev, "enable");
>>> +     if (IS_ERR(clk)) {
>>> +             ret = PTR_ERR(clk);
>>> +             goto pltfm_free;
>>> +     }
>>> +     sprd_host->clk_enable = clk;
>>> +
>>> +     ret = clk_prepare_enable(sprd_host->clk_sdio);
>>> +     if (ret)
>>> +             goto pltfm_free;
>>> +
>>> +     clk_prepare_enable(sprd_host->clk_enable);
>>> +     if (ret)
>>> +             goto clk_disable;
>>> +
>>> +     sdhci_sprd_init_config(host);
>>> +     host->version = sdhci_readw(host, SDHCI_HOST_VERSION);
>>> +     sprd_host->version = ((host->version & SDHCI_VENDOR_VER_MASK) >>
>>> +                            SDHCI_VENDOR_VER_SHIFT);
>>> +
>>> +     pm_runtime_get_noresume(&pdev->dev);
>>> +     pm_runtime_set_active(&pdev->dev);
>>> +     pm_runtime_enable(&pdev->dev);
>>> +     pm_runtime_set_autosuspend_delay(&pdev->dev, 50);
>>> +     pm_runtime_use_autosuspend(&pdev->dev);
>>> +     pm_suspend_ignore_children(&pdev->dev, 1);
>>> +
>>> +     sdhci_enable_v4_mode(host);
>>> +     ret = sdhci_add_host(host);
>>> +     if (ret) {
>>> +             dev_err(&pdev->dev, "failed to add mmc host: %d\n", ret);
>>> +             goto pm_runtime_disable;
>>> +     }
>>> +
>>> +     pm_runtime_mark_last_busy(&pdev->dev);
>>> +     pm_runtime_put_autosuspend(&pdev->dev);
>>> +
>>> +     return 0;
>>> +
>>> +pm_runtime_disable:
>>> +     pm_runtime_disable(&pdev->dev);
>>> +     pm_runtime_set_suspended(&pdev->dev);
>>> +
>>> +     clk_disable_unprepare(sprd_host->clk_enable);
>>> +
>>> +clk_disable:
>>> +     clk_disable_unprepare(sprd_host->clk_sdio);
>>> +
>>> +pltfm_free:
>>> +     sdhci_pltfm_free(pdev);
>>> +     return ret;
>>> +}
>>> +
>>> +static int sdhci_sprd_remove(struct platform_device *pdev)
>>> +{
>>> +     struct sdhci_host *host = platform_get_drvdata(pdev);
>>> +     struct sdhci_sprd_host *sprd_host = TO_SPRD_HOST(host);
>>> +     struct mmc_host *mmc = host->mmc;
>>> +
>>> +     mmc_remove_host(mmc);
>>> +     clk_disable_unprepare(sprd_host->clk_sdio);
>>> +     clk_disable_unprepare(sprd_host->clk_enable);
>>> +
>>> +     mmc_free_host(mmc);
>>> +
>>> +     return 0;
>>> +}
>>> +
>>> +static const struct of_device_id sdhci_sprd_of_match[] = {
>>> +     { .compatible = "sprd,sdhci-r11", },
>>> +     { }
>>> +};
>>> +MODULE_DEVICE_TABLE(of, sdhci_sprd_of_match);
>>> +
>>> +#ifdef CONFIG_PM
>>> +static int sdhci_sprd_runtime_suspend(struct device *dev)
>>> +{
>>> +     struct sdhci_host *host = dev_get_drvdata(dev);
>>> +     struct sdhci_sprd_host *sprd_host = TO_SPRD_HOST(host);
>>> +
>>> +     sdhci_runtime_suspend_host(host);
>>> +
>>> +     clk_disable_unprepare(sprd_host->clk_sdio);
>>> +     clk_disable_unprepare(sprd_host->clk_enable);
>>> +
>>> +     return 0;
>>> +}
>>> +
>>> +static int sdhci_sprd_runtime_resume(struct device *dev)
>>> +{
>>> +     struct sdhci_host *host = dev_get_drvdata(dev);
>>> +     struct sdhci_sprd_host *sprd_host = TO_SPRD_HOST(host);
>>> +
>>> +     clk_prepare_enable(sprd_host->clk_enable);
>>> +     clk_prepare_enable(sprd_host->clk_sdio);
>>
>> Drivers usually check the error returns of clk_prepare_enable().
>>
>>> +
>>> +     sdhci_runtime_resume_host(host);
>>> +
>>> +     return 0;
>>> +}
>>> +#endif
>>> +
>>> +static const struct dev_pm_ops sdhci_sprd_pm_ops = {
>>> +     SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
>>> +                             pm_runtime_force_resume)
>>> +     SET_RUNTIME_PM_OPS(sdhci_sprd_runtime_suspend,
>>> +                        sdhci_sprd_runtime_resume, NULL)
>>> +};
>>> +
>>> +static struct platform_driver sdhci_sprd_driver = {
>>> +     .probe = sdhci_sprd_probe,
>>> +     .remove = sdhci_sprd_remove,
>>> +     .driver = {
>>> +             .name = "sdhci_sprd_r11",
>>> +             .of_match_table = of_match_ptr(sdhci_sprd_of_match),
>>> +             .pm = &sdhci_sprd_pm_ops,
>>> +     },
>>> +};
>>> +module_platform_driver(sdhci_sprd_driver);
>>> +
>>> +MODULE_DESCRIPTION("Spreadtrum sdio host controller r11 driver");
>>> +MODULE_LICENSE("GPL v2");
>>> +MODULE_ALIAS("platform:sdhci-sprd-r11");
>>>
>>
> 

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