[PATCH RFC] Toggle fifo write clk after ungating sdcc clk

[PATCH RFC] Toggle fifo write clk after ungating sdcc clk

[Sayali Lokhande]

During GCC level clock gating of MCLK, the async FIFO
gets into some hang condition, such that for the next
transfer after MCLK ungating, first bit of CMD response
doesn't get written in to the FIFO. This cause the CPSM
to hang eventually leading to SW timeout.

To fix the issue, toggle the FIFO write clock after
MCLK ungated to get the FIFO pointers and flags to
valid states.

Ram Prakash Gupta (1):
  mmc: sdhci-msm: Toggle fifo write clk after ungating sdcc clk

 drivers/mmc/host/sdhci-msm.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH RFC] mmc: sdhci-msm: Toggle fifo write clk after ungating sdcc clk

[Sayali Lokhande]

From: Ram Prakash Gupta <rampraka@codeaurora.org>

During GCC level clock gating of MCLK, the async FIFO
gets into some hang condition, such that for the next
transfer after MCLK ungating, first bit of CMD response
doesn't get written in to the FIFO. This cause the CPSM
to hang eventually leading to SW timeout.

To fix the issue, toggle the FIFO write clock after
MCLK ungated to get the FIFO pointers and flags to
valid states.

Change-Id: Ibef2d1d283ac0b6983c609a4abc98bc574d31fa6
Signed-off-by: Ram Prakash Gupta <rampraka@codeaurora.org>
Signed-off-by: Sayali Lokhande <sayalil@codeaurora.org>
---
 drivers/mmc/host/sdhci-msm.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
index c3a160c..eaa3e95 100644
--- a/drivers/mmc/host/sdhci-msm.c
+++ b/drivers/mmc/host/sdhci-msm.c
@@ -127,6 +127,8 @@
 #define CQHCI_VENDOR_CFG1	0xA00
 #define CQHCI_VENDOR_DIS_RST_ON_CQ_EN	(0x3 << 13)
 
+#define RCLK_TOGGLE 0x2
+
 struct sdhci_msm_offset {
 	u32 core_hc_mode;
 	u32 core_mci_data_cnt;
@@ -1554,6 +1556,43 @@ static void __sdhci_msm_set_clock(struct sdhci_host *host, unsigned int clock)
 	sdhci_enable_clk(host, clk);
 }
 
+/*
+ * After MCLK ugating, toggle the FIFO write clock to get
+ * the FIFO pointers and flags to valid state.
+ */
+static void sdhci_msm_toggle_fifo_write_clk(struct sdhci_host *host)
+{
+	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
+	struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
+	const struct sdhci_msm_offset *msm_offset =
+					msm_host->offset;
+	struct mmc_card *card = host->mmc->card;
+
+	if (msm_host->tuning_done ||
+			(card && card->ext_csd.strobe_support &&
+			card->host->ios.enhanced_strobe)) {
+		/*
+		 * set HC_REG_DLL_CONFIG_3[1] to select MCLK as
+		 * DLL input clock
+		 */
+		writel_relaxed(((readl_relaxed(host->ioaddr +
+			msm_offset->core_dll_config_3))
+			| RCLK_TOGGLE), host->ioaddr +
+			msm_offset->core_dll_config_3);
+		/* ensure above write as toggling same bit quickly */
+		wmb();
+		udelay(2);
+		/*
+		 * clear HC_REG_DLL_CONFIG_3[1] to select RCLK as
+		 * DLL input clock
+		 */
+		writel_relaxed(((readl_relaxed(host->ioaddr +
+			msm_offset->core_dll_config_3))
+			& ~RCLK_TOGGLE), host->ioaddr +
+			msm_offset->core_dll_config_3);
+	}
+}
+
 /* sdhci_msm_set_clock - Called with (host->lock) spinlock held. */
 static void sdhci_msm_set_clock(struct sdhci_host *host, unsigned int clock)
 {
@@ -2149,6 +2188,10 @@ static __maybe_unused int sdhci_msm_runtime_resume(struct device *dev)
 				       msm_host->bulk_clks);
 	if (ret)
 		return ret;
+	if (host->mmc &&
+			(host->mmc->ios.timing == MMC_TIMING_MMC_HS400))
+		sdhci_msm_toggle_fifo_write_clk(host);
+
 	/*
 	 * Whenever core-clock is gated dynamically, it's needed to
 	 * restore the SDR DLL settings when the clock is ungated.
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Re: [PATCH RFC] mmc: sdhci-msm: Toggle fifo write clk after ungating sdcc clk

[Bjorn Andersson]

On Thu 20 Feb 01:20 PST 2020, Sayali Lokhande wrote:

> From: Ram Prakash Gupta <rampraka@codeaurora.org>
> 
> During GCC level clock gating of MCLK, the async FIFO
> gets into some hang condition, such that for the next
> transfer after MCLK ungating, first bit of CMD response
> doesn't get written in to the FIFO. This cause the CPSM
> to hang eventually leading to SW timeout.

Does this always happen, on what platforms does this happen? How does
this manifest itself? Can you please elaborate.

> 
> To fix the issue, toggle the FIFO write clock after
> MCLK ungated to get the FIFO pointers and flags to
> valid states.
> 
> Change-Id: Ibef2d1d283ac0b6983c609a4abc98bc574d31fa6

Please drop the Change-Id and please add

Cc: stable@vger.kernel.org

If this is a bug fix that should be backported to e.g. 5.4.

> Signed-off-by: Ram Prakash Gupta <rampraka@codeaurora.org>
> Signed-off-by: Sayali Lokhande <sayalil@codeaurora.org>
> ---
>  drivers/mmc/host/sdhci-msm.c | 43 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 43 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> index c3a160c..eaa3e95 100644
> --- a/drivers/mmc/host/sdhci-msm.c
> +++ b/drivers/mmc/host/sdhci-msm.c
> @@ -127,6 +127,8 @@
>  #define CQHCI_VENDOR_CFG1	0xA00
>  #define CQHCI_VENDOR_DIS_RST_ON_CQ_EN	(0x3 << 13)
>  
> +#define RCLK_TOGGLE 0x2

Please use BIT(1) instead.

> +
>  struct sdhci_msm_offset {
>  	u32 core_hc_mode;
>  	u32 core_mci_data_cnt;
> @@ -1554,6 +1556,43 @@ static void __sdhci_msm_set_clock(struct sdhci_host *host, unsigned int clock)
>  	sdhci_enable_clk(host, clk);
>  }
>  
> +/*
> + * After MCLK ugating, toggle the FIFO write clock to get
> + * the FIFO pointers and flags to valid state.
> + */
> +static void sdhci_msm_toggle_fifo_write_clk(struct sdhci_host *host)
> +{
> +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> +	struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
> +	const struct sdhci_msm_offset *msm_offset =
> +					msm_host->offset;

This doesn't look to be > 80 chars, please unwrap.

> +	struct mmc_card *card = host->mmc->card;
> +
> +	if (msm_host->tuning_done ||
> +			(card && card->ext_csd.strobe_support &&
> +			card->host->ios.enhanced_strobe)) {
> +		/*
> +		 * set HC_REG_DLL_CONFIG_3[1] to select MCLK as
> +		 * DLL input clock

You can shorten this to /* Select MCLK as DLL input clock */ if you make
the below readl/writel a little bit easier to read.

> +		 */
> +		writel_relaxed(((readl_relaxed(host->ioaddr +
> +			msm_offset->core_dll_config_3))
> +			| RCLK_TOGGLE), host->ioaddr +
> +			msm_offset->core_dll_config_3);

Please use a local variable and write this out as:
		val = readl(addr);
		val |= RCLK_TOGGLE;
		writel(val, addr);

> +		/* ensure above write as toggling same bit quickly */
> +		wmb();

This ensures ordering of writes, if you want to make sure the write has
hit the hardware before the delay perform a readl() on the address.

> +		udelay(2);
> +		/*
> +		 * clear HC_REG_DLL_CONFIG_3[1] to select RCLK as
> +		 * DLL input clock
> +		 */

		/* Select RCLK as DLL input clock */

> +		writel_relaxed(((readl_relaxed(host->ioaddr +
> +			msm_offset->core_dll_config_3))
> +			& ~RCLK_TOGGLE), host->ioaddr +
> +			msm_offset->core_dll_config_3);

Same as above, readl(); val &= ~RCLK_TOGGLE; writel(); will make this
easier on the eyes.

> +	}
> +}
> +
>  /* sdhci_msm_set_clock - Called with (host->lock) spinlock held. */
>  static void sdhci_msm_set_clock(struct sdhci_host *host, unsigned int clock)
>  {
> @@ -2149,6 +2188,10 @@ static __maybe_unused int sdhci_msm_runtime_resume(struct device *dev)
>  				       msm_host->bulk_clks);
>  	if (ret)
>  		return ret;

An empty line please.

> +	if (host->mmc &&

Afaict host->mmc can't be NULL, can you please confirm that you need
this check.

> +			(host->mmc->ios.timing == MMC_TIMING_MMC_HS400))
> +		sdhci_msm_toggle_fifo_write_clk(host);
> +

Regards,
Bjorn

>  	/*
>  	 * Whenever core-clock is gated dynamically, it's needed to
>  	 * restore the SDR DLL settings when the clock is ungated.
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project

Re: [PATCH RFC] Toggle fifo write clk after ungating sdcc clk

[Bjorn Andersson]

On Thu 20 Feb 01:20 PST 2020, Sayali Lokhande wrote:

> During GCC level clock gating of MCLK, the async FIFO
> gets into some hang condition, such that for the next
> transfer after MCLK ungating, first bit of CMD response
> doesn't get written in to the FIFO. This cause the CPSM
> to hang eventually leading to SW timeout.
> 
> To fix the issue, toggle the FIFO write clock after
> MCLK ungated to get the FIFO pointers and flags to
> valid states.
> 

Please don't provide cover letters for a single patch.

Regards,
Bjorn

> Ram Prakash Gupta (1):
>   mmc: sdhci-msm: Toggle fifo write clk after ungating sdcc clk
> 
>  drivers/mmc/host/sdhci-msm.c | 43 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 43 insertions(+)
> 
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project

Re: [PATCH RFC] mmc: sdhci-msm: Toggle fifo write clk after ungating sdcc clk

[Stephen Boyd]

Quoting Sayali Lokhande (2020-02-20 01:20:46)
> From: Ram Prakash Gupta <rampraka@codeaurora.org>
> 
> During GCC level clock gating of MCLK, the async FIFO

Is this automatic hardware clock gating?

> gets into some hang condition, such that for the next
> transfer after MCLK ungating, first bit of CMD response
> doesn't get written in to the FIFO. This cause the CPSM
> to hang eventually leading to SW timeout.
> 
> To fix the issue, toggle the FIFO write clock after
> MCLK ungated to get the FIFO pointers and flags to
> valid states.
> 
> Change-Id: Ibef2d1d283ac0b6983c609a4abc98bc574d31fa6
> Signed-off-by: Ram Prakash Gupta <rampraka@codeaurora.org>
> Signed-off-by: Sayali Lokhande <sayalil@codeaurora.org>
> ---
>  drivers/mmc/host/sdhci-msm.c | 43 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 43 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> index c3a160c..eaa3e95 100644
> --- a/drivers/mmc/host/sdhci-msm.c
> +++ b/drivers/mmc/host/sdhci-msm.c
> @@ -1554,6 +1556,43 @@ static void __sdhci_msm_set_clock(struct sdhci_host *host, unsigned int clock)
>         sdhci_enable_clk(host, clk);
>  }
>  
> +/*
> + * After MCLK ugating, toggle the FIFO write clock to get

What is ugating?

> + * the FIFO pointers and flags to valid state.
> + */
> +static void sdhci_msm_toggle_fifo_write_clk(struct sdhci_host *host)
> +{
> +       struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> +       struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
> +       const struct sdhci_msm_offset *msm_offset =
> +                                       msm_host->offset;
> +       struct mmc_card *card = host->mmc->card;
> +
> +       if (msm_host->tuning_done ||
> +                       (card && card->ext_csd.strobe_support &&
> +                       card->host->ios.enhanced_strobe)) {
> +               /*
> +                * set HC_REG_DLL_CONFIG_3[1] to select MCLK as
> +                * DLL input clock
> +                */

Re: [PATCH RFC] mmc: sdhci-msm: Toggle fifo write clk after ungating sdcc clk

[Veerabhadrarao Badiganti]

On 2/20/2020 2:50 PM, Sayali Lokhande wrote:
> From: Ram Prakash Gupta <rampraka@codeaurora.org>
>
> During GCC level clock gating of MCLK, the async FIFO
> gets into some hang condition, such that for the next
> transfer after MCLK ungating, first bit of CMD response
> doesn't get written in to the FIFO. This cause the CPSM
> to hang eventually leading to SW timeout.
>
> To fix the issue, toggle the FIFO write clock after
> MCLK ungated to get the FIFO pointers and flags to
> valid states.
>
> Change-Id: Ibef2d1d283ac0b6983c609a4abc98bc574d31fa6
> Signed-off-by: Ram Prakash Gupta <rampraka@codeaurora.org>
> Signed-off-by: Sayali Lokhande <sayalil@codeaurora.org>
> ---
>   drivers/mmc/host/sdhci-msm.c | 43 +++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 43 insertions(+)
>
> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> index c3a160c..eaa3e95 100644
> --- a/drivers/mmc/host/sdhci-msm.c
> +++ b/drivers/mmc/host/sdhci-msm.c
> @@ -127,6 +127,8 @@
>   #define CQHCI_VENDOR_CFG1	0xA00
>   #define CQHCI_VENDOR_DIS_RST_ON_CQ_EN	(0x3 << 13)
>   
> +#define RCLK_TOGGLE 0x2
> +
>   struct sdhci_msm_offset {
>   	u32 core_hc_mode;
>   	u32 core_mci_data_cnt;
> @@ -1554,6 +1556,43 @@ static void __sdhci_msm_set_clock(struct sdhci_host *host, unsigned int clock)
>   	sdhci_enable_clk(host, clk);
>   }
>   
> +/*
> + * After MCLK ugating, toggle the FIFO write clock to get
> + * the FIFO pointers and flags to valid state.
> + */
> +static void sdhci_msm_toggle_fifo_write_clk(struct sdhci_host *host)
> +{
> +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> +	struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
> +	const struct sdhci_msm_offset *msm_offset =
> +					msm_host->offset;
> +	struct mmc_card *card = host->mmc->card;
> +
> +	if (msm_host->tuning_done ||
> +			(card && card->ext_csd.strobe_support &&
> +			card->host->ios.enhanced_strobe)) {

This issue is present on only HS400ES mode.

If(host->ios.enhanced_strob) check should be sufficient, other checks 
are not needed.

> +		/*
> +		 * set HC_REG_DLL_CONFIG_3[1] to select MCLK as
> +		 * DLL input clock
> +		 */
> +		writel_relaxed(((readl_relaxed(host->ioaddr +
> +			msm_offset->core_dll_config_3))
> +			| RCLK_TOGGLE), host->ioaddr +
> +			msm_offset->core_dll_config_3);
> +		/* ensure above write as toggling same bit quickly */
> +		wmb();
> +		udelay(2);
> +		/*
> +		 * clear HC_REG_DLL_CONFIG_3[1] to select RCLK as
> +		 * DLL input clock
> +		 */
> +		writel_relaxed(((readl_relaxed(host->ioaddr +
> +			msm_offset->core_dll_config_3))
> +			& ~RCLK_TOGGLE), host->ioaddr +
> +			msm_offset->core_dll_config_3);
> +	}
> +}
> +
>   /* sdhci_msm_set_clock - Called with (host->lock) spinlock held. */
>   static void sdhci_msm_set_clock(struct sdhci_host *host, unsigned int clock)
>   {
> @@ -2149,6 +2188,10 @@ static __maybe_unused int sdhci_msm_runtime_resume(struct device *dev)
>   				       msm_host->bulk_clks);
>   	if (ret)
>   		return ret;
> +	if (host->mmc &&
> +			(host->mmc->ios.timing == MMC_TIMING_MMC_HS400))
These checks are not needed. You can have these checks within 
sdhci_msm_toggle_fifo_write_clk
> +		sdhci_msm_toggle_fifo_write_clk(host);
> +
>   	/*
>   	 * Whenever core-clock is gated dynamically, it's needed to
>   	 * restore the SDR DLL settings when the clock is ungated.

Re: [PATCH RFC] mmc: sdhci-msm: Toggle fifo write clk after ungating sdcc clk

[Sayali Lokhande]

Hi Veera,

On 2/24/2020 7:19 PM, Veerabhadrarao Badiganti wrote:
>
> On 2/20/2020 2:50 PM, Sayali Lokhande wrote:
>> From: Ram Prakash Gupta <rampraka@codeaurora.org>
>>
>> During GCC level clock gating of MCLK, the async FIFO
>> gets into some hang condition, such that for the next
>> transfer after MCLK ungating, first bit of CMD response
>> doesn't get written in to the FIFO. This cause the CPSM
>> to hang eventually leading to SW timeout.
>>
>> To fix the issue, toggle the FIFO write clock after
>> MCLK ungated to get the FIFO pointers and flags to
>> valid states.
>>
>> Change-Id: Ibef2d1d283ac0b6983c609a4abc98bc574d31fa6
>> Signed-off-by: Ram Prakash Gupta <rampraka@codeaurora.org>
>> Signed-off-by: Sayali Lokhande <sayalil@codeaurora.org>
>> ---
>>   drivers/mmc/host/sdhci-msm.c | 43 
>> +++++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 43 insertions(+)
>>
>> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
>> index c3a160c..eaa3e95 100644
>> --- a/drivers/mmc/host/sdhci-msm.c
>> +++ b/drivers/mmc/host/sdhci-msm.c
>> @@ -127,6 +127,8 @@
>>   #define CQHCI_VENDOR_CFG1    0xA00
>>   #define CQHCI_VENDOR_DIS_RST_ON_CQ_EN    (0x3 << 13)
>>   +#define RCLK_TOGGLE 0x2
>> +
>>   struct sdhci_msm_offset {
>>       u32 core_hc_mode;
>>       u32 core_mci_data_cnt;
>> @@ -1554,6 +1556,43 @@ static void __sdhci_msm_set_clock(struct 
>> sdhci_host *host, unsigned int clock)
>>       sdhci_enable_clk(host, clk);
>>   }
>>   +/*
>> + * After MCLK ugating, toggle the FIFO write clock to get
>> + * the FIFO pointers and flags to valid state.
>> + */
>> +static void sdhci_msm_toggle_fifo_write_clk(struct sdhci_host *host)
>> +{
>> +    struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
>> +    struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
>> +    const struct sdhci_msm_offset *msm_offset =
>> +                    msm_host->offset;
>> +    struct mmc_card *card = host->mmc->card;
>> +
>> +    if (msm_host->tuning_done ||
>> +            (card && card->ext_csd.strobe_support &&
>> +            card->host->ios.enhanced_strobe)) {
>
> This issue is present on only HS400ES mode.
>
> If(host->ios.enhanced_strob) check should be sufficient, other checks 
> are not needed.
Agree, Will update.
>
>> +        /*
>> +         * set HC_REG_DLL_CONFIG_3[1] to select MCLK as
>> +         * DLL input clock
>> +         */
>> +        writel_relaxed(((readl_relaxed(host->ioaddr +
>> +            msm_offset->core_dll_config_3))
>> +            | RCLK_TOGGLE), host->ioaddr +
>> +            msm_offset->core_dll_config_3);
>> +        /* ensure above write as toggling same bit quickly */
>> +        wmb();
>> +        udelay(2);
>> +        /*
>> +         * clear HC_REG_DLL_CONFIG_3[1] to select RCLK as
>> +         * DLL input clock
>> +         */
>> +        writel_relaxed(((readl_relaxed(host->ioaddr +
>> +            msm_offset->core_dll_config_3))
>> +            & ~RCLK_TOGGLE), host->ioaddr +
>> +            msm_offset->core_dll_config_3);
>> +    }
>> +}
>> +
>>   /* sdhci_msm_set_clock - Called with (host->lock) spinlock held. */
>>   static void sdhci_msm_set_clock(struct sdhci_host *host, unsigned 
>> int clock)
>>   {
>> @@ -2149,6 +2188,10 @@ static __maybe_unused int 
>> sdhci_msm_runtime_resume(struct device *dev)
>>                          msm_host->bulk_clks);
>>       if (ret)
>>           return ret;
>> +    if (host->mmc &&
>> +            (host->mmc->ios.timing == MMC_TIMING_MMC_HS400))
> These checks are not needed. You can have these checks within 
> sdhci_msm_toggle_fifo_write_clk
Agree. Will update.
>> + sdhci_msm_toggle_fifo_write_clk(host);
>> +
>>       /*
>>        * Whenever core-clock is gated dynamically, it's needed to
>>        * restore the SDR DLL settings when the clock is ungated.