Re: [PATCH V3] mmc: sdhci-msm: Reset GCC_SDCC_BCR register for SDHC

[Bjorn Andersson <bjorn.andersson@linaro.org>]

On Thu 31 Mar 00:03 PDT 2022, Shaik Sajida Bhanu wrote:

> Reset GCC_SDCC_BCR register before every fresh initilazation. This will
> reset whole SDHC-msm controller, clears the previous power control
> states and avoids, software reset timeout issues as below.
> 
> [ 5.458061][ T262] mmc1: Reset 0x1 never completed.
> [ 5.462454][ T262] mmc1: sdhci: ============ SDHCI REGISTER DUMP ===========
> [ 5.469065][ T262] mmc1: sdhci: Sys addr: 0x00000000 | Version: 0x00007202
> [ 5.475688][ T262] mmc1: sdhci: Blk size: 0x00000000 | Blk cnt: 0x00000000
> [ 5.482315][ T262] mmc1: sdhci: Argument: 0x00000000 | Trn mode: 0x00000000
> [ 5.488927][ T262] mmc1: sdhci: Present: 0x01f800f0 | Host ctl: 0x00000000
> [ 5.495539][ T262] mmc1: sdhci: Power: 0x00000000 | Blk gap: 0x00000000
> [ 5.502162][ T262] mmc1: sdhci: Wake-up: 0x00000000 | Clock: 0x00000003
> [ 5.508768][ T262] mmc1: sdhci: Timeout: 0x00000000 | Int stat: 0x00000000
> [ 5.515381][ T262] mmc1: sdhci: Int enab: 0x00000000 | Sig enab: 0x00000000
> [ 5.521996][ T262] mmc1: sdhci: ACmd stat: 0x00000000 | Slot int: 0x00000000
> [ 5.528607][ T262] mmc1: sdhci: Caps: 0x362dc8b2 | Caps_1: 0x0000808f
> [ 5.535227][ T262] mmc1: sdhci: Cmd: 0x00000000 | Max curr: 0x00000000
> [ 5.541841][ T262] mmc1: sdhci: Resp[0]: 0x00000000 | Resp[1]: 0x00000000
> [ 5.548454][ T262] mmc1: sdhci: Resp[2]: 0x00000000 | Resp[3]: 0x00000000
> [ 5.555079][ T262] mmc1: sdhci: Host ctl2: 0x00000000
> [ 5.559651][ T262] mmc1: sdhci_msm: ----------- VENDOR REGISTER DUMP-----------
> [ 5.566621][ T262] mmc1: sdhci_msm: DLL sts: 0x00000000 | DLL cfg: 0x6000642c | DLL cfg2: 0x0020a000
> [ 5.575465][ T262] mmc1: sdhci_msm: DLL cfg3: 0x00000000 | DLL usr ctl: 0x00010800 | DDR cfg: 0x80040873
> [ 5.584658][ T262] mmc1: sdhci_msm: Vndr func: 0x00018a9c | Vndr func2 : 0xf88218a8 Vndr func3: 0x02626040
> 
> Fixes: 0eb0d9f4de34 ("mmc: sdhci-msm: Initial support for Qualcomm chipsets")
> Signed-off-by: Shaik Sajida Bhanu <quic_c_sbhanu@quicinc.com>
> ---
> 
> Changes since V2:
> 	- Dropped new line after fixes tag as suggested by Bjorn
> 	  Andersson.
> 	- Passed device structure instead of passing platform_device
> 	  structure as a argument for sdhci_msm_gcc_reset() as suggested
> 	  by Bjorn Andersson.
> 	- Replaced dev_err() with dev_err_probe() as suggested by Bjorn
> 	  Andersson.

Thanks, looks much better. Still some things I would like to see
improved below.

> Changes since V1:
> 	- Added fixes tag as suggested by Ulf Hansson.
> 	- Replaced devm_reset_control_get() with
> 	  devm_reset_control_get_optional_exclusive() as suggested by
> 	  Ulf Hansson.
> ---
>  drivers/mmc/host/sdhci-msm.c | 39 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> index 50c71e0..e15e789 100644
> --- a/drivers/mmc/host/sdhci-msm.c
> +++ b/drivers/mmc/host/sdhci-msm.c
> @@ -17,6 +17,7 @@
>  #include <linux/regulator/consumer.h>
>  #include <linux/interconnect.h>
>  #include <linux/pinctrl/consumer.h>
> +#include <linux/reset.h>
>  
>  #include "sdhci-pltfm.h"
>  #include "cqhci.h"
> @@ -284,6 +285,7 @@ struct sdhci_msm_host {
>  	bool uses_tassadar_dll;
>  	u32 dll_config;
>  	u32 ddr_config;
> +	struct reset_control *core_reset;
>  	bool vqmmc_enabled;
>  };
>  
> @@ -2482,6 +2484,39 @@ static inline void sdhci_msm_get_of_property(struct platform_device *pdev,
>  	of_property_read_u32(node, "qcom,dll-config", &msm_host->dll_config);
>  }
>  
> +static int sdhci_msm_gcc_reset(struct device *dev, struct sdhci_host *host)
> +{
> +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> +	struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
> +	int ret = 0;

First use of this variable is an assignment, so no need to initialize it
here.

> +
> +	msm_host->core_reset = devm_reset_control_get_optional_exclusive(dev, "core_reset");

reset-names will only be used to identify resets and hence there's no
reason to include "_reset" in the identifier.

If this is the only reset for the controller, there's actually no reason
for identifying it, you can omit reset-names from the binding and just
pass NULL here (to get the first resets = <>).

> +	if (IS_ERR(msm_host->core_reset))
> +		return dev_err_probe(dev, PTR_ERR(msm_host->core_reset),
> +				"unable to acquire core_reset\n");
> +
> +	if (!msm_host->core_reset)
> +		return 0;
> +
> +	ret = reset_control_assert(msm_host->core_reset);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "core_reset assert failed\n");
> +
> +	/*
> +	 * The hardware requirement for delay between assert/deassert
> +	 * is at least 3-4 sleep clock (32.7KHz) cycles, which comes to
> +	 * ~125us (4/32768). To be on the safe side add 200us delay.
> +	 */
> +	usleep_range(200, 210);
> +
> +	ret = reset_control_deassert(msm_host->core_reset);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "core_reset deassert failed\n");
> +
> +	usleep_range(200, 210);
> +

sdhci_msm_gcc_reset() is only called once during probe(), so there's no
reason to carry the reset_control pointer in struct sdhci_msm_host. Make
it a local variable and use reset_control_get_optional_exclusive() and
reset_control_put() the reset here before returning.

Regards,
Bjorn

> +	return 0;
> +}
>  
>  static int sdhci_msm_probe(struct platform_device *pdev)
>  {
> @@ -2529,6 +2564,10 @@ static int sdhci_msm_probe(struct platform_device *pdev)
>  
>  	msm_host->saved_tuning_phase = INVALID_TUNING_PHASE;
>  
> +	ret = sdhci_msm_gcc_reset(&pdev->dev, host);
> +	if (ret)
> +		goto pltfm_free;
> +
>  	/* Setup SDCC bus voter clock. */
>  	msm_host->bus_clk = devm_clk_get(&pdev->dev, "bus");
>  	if (!IS_ERR(msm_host->bus_clk)) {
> -- 
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