linux-kernel - Re: [PATCH V2 1/3] mmc: sdhci-msm: Enable tuning for SDR50 mode for SD card

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Message-ID: <177e21cc-0a9b-4543-8135-f4da424f5713@intel.com>
Date: Wed, 28 May 2025 14:32:20 +0300
From: Adrian Hunter <adrian.hunter@...el.com>
To: Sarthak Garg <quic_sartgarg@...cinc.com>, Bjorn Andersson
	<andersson@...nel.org>, Konrad Dybcio <konradybcio@...nel.org>, Rob Herring
	<robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
	<conor+dt@...nel.org>, Ulf Hansson <ulf.hansson@...aro.org>
CC: <linux-arm-msm@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-mmc@...r.kernel.org>,
	<quic_cang@...cinc.com>, <quic_nguyenb@...cinc.com>,
	<quic_rampraka@...cinc.com>, <quic_pragalla@...cinc.com>,
	<quic_sayalil@...cinc.com>, <quic_nitirawa@...cinc.com>,
	<quic_bhaskarv@...cinc.com>
Subject: Re: [PATCH V2 1/3] mmc: sdhci-msm: Enable tuning for SDR50 mode for
 SD card

On 23/05/2025 13:57, Sarthak Garg wrote:
> For Qualcomm SoCs which needs level shifter for SD card, extra delay is
> seen on receiver data path.
> 
> To compensate this delay enable tuning for SDR50 mode for targets which
> has level shifter. SDHCI_SDR50_NEEDS_TUNING caps will be set for targets
> with level shifter on Qualcomm SOC's.
> 
> Signed-off-by: Sarthak Garg <quic_sartgarg@...cinc.com>

Assuming this is still needed even with new generic quirk approach:

Acked-by: Adrian Hunter <adrian.hunter@...el.com>

> ---
>  drivers/mmc/host/sdhci-msm.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> index 66c0d1ba2a33..bf91cb96a0ea 100644
> --- a/drivers/mmc/host/sdhci-msm.c
> +++ b/drivers/mmc/host/sdhci-msm.c
> @@ -81,6 +81,7 @@
>  #define CORE_IO_PAD_PWR_SWITCH_EN	BIT(15)
>  #define CORE_IO_PAD_PWR_SWITCH	BIT(16)
>  #define CORE_HC_SELECT_IN_EN	BIT(18)
> +#define CORE_HC_SELECT_IN_SDR50	(4 << 19)
>  #define CORE_HC_SELECT_IN_HS400	(6 << 19)
>  #define CORE_HC_SELECT_IN_MASK	(7 << 19)
>  
> @@ -1133,6 +1134,10 @@ static bool sdhci_msm_is_tuning_needed(struct sdhci_host *host)
>  {
>  	struct mmc_ios *ios = &host->mmc->ios;
>  
> +	if (ios->timing == MMC_TIMING_UHS_SDR50 &&
> +	    host->flags & SDHCI_SDR50_NEEDS_TUNING)
> +		return true;
> +
>  	/*
>  	 * Tuning is required for SDR104, HS200 and HS400 cards and
>  	 * if clock frequency is greater than 100MHz in these modes.
> @@ -1201,6 +1206,8 @@ static int sdhci_msm_execute_tuning(struct mmc_host *mmc, u32 opcode)
>  	struct mmc_ios ios = host->mmc->ios;
>  	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;
> +	u32 config;
>  
>  	if (!sdhci_msm_is_tuning_needed(host)) {
>  		msm_host->use_cdr = false;
> @@ -1217,6 +1224,14 @@ static int sdhci_msm_execute_tuning(struct mmc_host *mmc, u32 opcode)
>  	 */
>  	msm_host->tuning_done = 0;
>  
> +	if (ios.timing == MMC_TIMING_UHS_SDR50 &&
> +	    host->flags & SDHCI_SDR50_NEEDS_TUNING) {
> +		config = readl_relaxed(host->ioaddr + msm_offset->core_vendor_spec);
> +		config &= ~CORE_HC_SELECT_IN_MASK;
> +		config |= CORE_HC_SELECT_IN_EN | CORE_HC_SELECT_IN_SDR50;
> +		writel_relaxed(config, host->ioaddr + msm_offset->core_vendor_spec);
> +	}
> +
>  	/*
>  	 * For HS400 tuning in HS200 timing requires:
>  	 * - select MCLK/2 in VENDOR_SPEC