RE: [RFC PATCH 2/3] mmc: sdhci-esdhc-imx: add NXP S32G2 support

[Bough Chen]

> -----Original Message-----
> From: Chester Lin [mailto:clin@xxxxxxxx]
> Sent: 2021年10月21日 15:31
> To: Ulf Hansson <ulf.hansson@xxxxxxxxxx>; dl-S32 <S32@xxxxxxx>; dl-linux-imx
> <linux-imx@xxxxxxx>; Bough Chen <haibo.chen@xxxxxxx>; Aisheng Dong
> <aisheng.dong@xxxxxxx>; linux-mmc@xxxxxxxxxxxxxxx
> Cc: Rob Herring <robh+dt@xxxxxxxxxx>; Shawn Guo <shawnguo@xxxxxxxxxx>;
> Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>; Pengutronix Kernel Team
> <kernel@xxxxxxxxxxxxxx>; Fabio Estevam <festevam@xxxxxxxxx>;
> devicetree@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; Radu-nicolae Pirea (OSS)
> <radu-nicolae.pirea@xxxxxxxxxxx>; Andreas Färber <afaerber@xxxxxxx>;
> Matthias Brugger <mbrugger@xxxxxxxx>; Ivan T . Ivanov <iivanov@xxxxxxx>;
> Lee, Chun-Yi <jlee@xxxxxxxx>
> Subject: Re: [RFC PATCH 2/3] mmc: sdhci-esdhc-imx: add NXP S32G2 support
> 
> Hi NXP S32 and i.MX Linux teams,
> 
> On Thu, Oct 21, 2021 at 03:13:32PM +0800, Chester Lin wrote:
> > Support the SDHCI controller found on NXP S32G2 platform. The new flag
> > ESDHC_FLAG_SKIP_ERR004536 is used because the hardware erratum bit is
> > not applicable for S32G2.
> >
> > Signed-off-by: Chester Lin <clin@xxxxxxxx>
> > ---
> >  drivers/mmc/host/sdhci-esdhc-imx.c | 17 +++++++++++++++--
> >  1 file changed, 15 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c
> > b/drivers/mmc/host/sdhci-esdhc-imx.c
> > index f18d169bc8ff..d0f7d46a0354 100644
> > --- a/drivers/mmc/host/sdhci-esdhc-imx.c
> > +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
> > @@ -196,6 +196,9 @@
> >   */
> >  #define ESDHC_FLAG_BROKEN_AUTO_CMD23	BIT(16)
> >
> > +/* ERR004536 is not applicable for the IP  */
> > +#define ESDHC_FLAG_SKIP_ERR004536	BIT(17)
> > +
> >  enum wp_types {
> >  	ESDHC_WP_NONE,		/* no WP, neither controller nor gpio */
> >  	ESDHC_WP_CONTROLLER,	/* mmc controller internal WP */
> > @@ -289,6 +292,13 @@ static const struct esdhc_soc_data
> usdhc_imx7d_data = {
> >  			| ESDHC_FLAG_BROKEN_AUTO_CMD23,
> >  };
> >
> > +static struct esdhc_soc_data usdhc_s32g2_data = {
> > +	.flags = ESDHC_FLAG_USDHC | ESDHC_FLAG_MAN_TUNING
> > +			| ESDHC_FLAG_HAVE_CAP1 | ESDHC_FLAG_HS200
> > +			| ESDHC_FLAG_HS400 | ESDHC_FLAG_HS400_ES
> > +			| ESDHC_FLAG_SKIP_ERR004536,
> > +};
> > +
> >  static struct esdhc_soc_data usdhc_imx7ulp_data = {
> >  	.flags = ESDHC_FLAG_USDHC | ESDHC_FLAG_STD_TUNING
> >  			| ESDHC_FLAG_HAVE_CAP1 | ESDHC_FLAG_HS200 @@ -347,6
> +357,7 @@
> > 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 = "nxp,s32g2-usdhc", .data = &usdhc_s32g2_data, },
> >  	{ /* sentinel */ }
> >  };
> >  MODULE_DEVICE_TABLE(of, imx_esdhc_dt_ids); @@ -1359,8 +1370,10
> @@
> > static void sdhci_esdhc_imx_hwinit(struct sdhci_host *host)
> >  		 * erratum ESDHC_FLAG_ERR004536 fix for MX6Q TO1.2 and MX6DL
> >  		 * TO1.1, it's harmless for MX6SL
> >  		 */
> > -		writel(readl(host->ioaddr + 0x6c) & ~BIT(7),
> > -			host->ioaddr + 0x6c);
> > +		if (!(imx_data->socdata->flags & ESDHC_FLAG_SKIP_ERR004536)) {
> > +			writel(readl(host->ioaddr + 0x6c) & ~BIT(7),
> > +				host->ioaddr + 0x6c);
> > +		}
> 
> Hope you don't might that I raise this question here. Is it really necessary to
> unconditionally apply the erratum bit even if some SoCs might not need this
> workaround? From the S32 implementation in CodeAurora[1], I noticed that
> this bit is not required by S32V/S32G so I wonder if there's any better way to
> refine this part?
> 

I confirmed with IP owner before, for SoC contain this errata fixup, clear this bit 7
will enable the fixup, set the bit 7 will disable the fixup.
For SoC which do not contain this errata fixup, this bit 7 has no definition.
So it's okay to clear this bit 7 unconditionally.

Best Regards
Haibo Chen


> Thanks,
> Chester
> 
> [1]
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fsource.
> codeaurora.org%2Fexternal%2Fautobsps32%2Flinux%2Ftree%2Fdrivers%2Fm
> mc%2Fhost%2Fsdhci-esdhc-imx.c%3Fh%3Drelease%2Fbsp30.0-5.4-rt%23n1268
> &amp;data=04%7C01%7Chaibo.chen%40nxp.com%7Cec36a273354b4b66c45b
> 08d99464c449%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C63770
> 3982782606697%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJ
> QIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=hvzsy
> 3W%2FpKXBmXxS8%2F73huzb157a%2FuHa5G4lFWj5ABQ%3D&amp;reserved=
> 0
> 
> >
> >  		/* disable DLL_CTRL delay line settings */
> >  		writel(0x0, host->ioaddr + ESDHC_DLL_CTRL);
> > --
> > 2.30.0
> >

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