RE: [PATCH] mmc: sdhci-esdhc-imx: improve imx8mq emmc/sd read performance

[Bough Chen]

> -----Original Message-----
> From: Luke Wang <ziniu.wang_1@xxxxxxx>
> Sent: 2025年2月17日 19:06
> To: adrian.hunter@xxxxxxxxx; ulf.hansson@xxxxxxxxxx
> Cc: Bough Chen <haibo.chen@xxxxxxx>; shawnguo@xxxxxxxxxx;
> s.hauer@xxxxxxxxxxxxxx; kernel@xxxxxxxxxxxxxx; festevam@xxxxxxxxx;
> imx@xxxxxxxxxxxxxxx; linux-mmc@xxxxxxxxxxxxxxx; dl-S32 <S32@xxxxxxx>;
> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: [PATCH] mmc: sdhci-esdhc-imx: improve imx8mq emmc/sd read
> performance
> 
> From: Luke Wang <ziniu.wang_1@xxxxxxx>
> 
> Compared with kernel 6.1, imx8mq eMMC/SD read performance drops by about
> 30% with kernel 6.6.
> 
> The eMMC/SD read thread will be put to sleep until the hardware completes
> data transfer. Normally, the read thread will be woken up immediately when the
> data transfer is completed. However, due to a known ic bug, if imx8mq is in
> cpuidle, it will take a long time (about 500us) to exit cpuidle. As a result, the
> read thread cannot immediately read the next data block, affecting the read
> performance.
> 
> Kernel 6.6 uses EEVDF as the new scheduler, which affects cpu scheduling and
> cpuidle behavior. With kernel 6.6, the cpu which the read thread resides has a
> greater probability in cpuidle (about 80%), while with kernel 6.1, the probability
> is only about 20-30%. For other platforms, this does not have a significant impact
> on read performance because the cpuidle exit time is very short (for example,
> imx93 is about 60us). But for imx8mq, this results in longer waits for the thread
> to be woken up while reading eMMC/SD, which drops performance.
> 
> So for imx8mq, use the ESDHC_FLAG_PMQOS flag to request the cpu latency
> QoS constraint. This can prevent entering cpuidle during data transfer.

Reviewed-by: Haibo Chen <haibo.chen@xxxxxxx>

Regards
Haibo Chen
> 
> Signed-off-by: Luke Wang <ziniu.wang_1@xxxxxxx>
> ---
>  drivers/mmc/host/sdhci-esdhc-imx.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c
> b/drivers/mmc/host/sdhci-esdhc-imx.c
> index ff78a7c6a04c..b3bf9c171d46 100644
> --- a/drivers/mmc/host/sdhci-esdhc-imx.c
> +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
> @@ -337,6 +337,15 @@ static struct esdhc_soc_data usdhc_imx8mm_data = {
>  	.quirks = SDHCI_QUIRK_NO_LED,
>  };
> 
> +static struct esdhc_soc_data usdhc_imx8mq_data = {
> +	.flags = ESDHC_FLAG_USDHC | ESDHC_FLAG_STD_TUNING
> +			| ESDHC_FLAG_HAVE_CAP1 | ESDHC_FLAG_HS200
> +			| ESDHC_FLAG_HS400 | ESDHC_FLAG_PMQOS
> +			| ESDHC_FLAG_STATE_LOST_IN_LPMODE
> +			| ESDHC_FLAG_BROKEN_AUTO_CMD23,
> +	.quirks = SDHCI_QUIRK_NO_LED,
> +};
> +
>  struct pltfm_imx_data {
>  	u32 scratchpad;
>  	struct pinctrl *pinctrl;
> @@ -381,6 +390,7 @@ static const struct of_device_id imx_esdhc_dt_ids[] = {
>  	{ .compatible = "fsl,imx7ulp-usdhc", .data = &usdhc_imx7ulp_data, },
>  	{ .compatible = "fsl,imx8qxp-usdhc", .data = &usdhc_imx8qxp_data, },
>  	{ .compatible = "fsl,imx8mm-usdhc", .data = &usdhc_imx8mm_data, },
> +	{ .compatible = "fsl,imx8mq-usdhc", .data = &usdhc_imx8mq_data, },
>  	{ .compatible = "fsl,imxrt1050-usdhc", .data = &usdhc_imxrt1050_data, },
>  	{ .compatible = "nxp,s32g2-usdhc", .data = &usdhc_s32g2_data, },
>  	{ /* sentinel */ }
> --
> 2.34.1