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SubjectRE: [RFC PATCH] mmc: sdhci-of-arasan: Add auto tuning support for ZynqMP Platform
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> -----Original Message-----
> From: Adrian Hunter [mailto:adrian.hunter@intel.com]
> Sent: Thursday, February 22, 2018 1:50 PM
> To: Manish Narani <MNARANI@xilinx.com>; michal.simek@xilinx.com;
> ulf.hansson@linaro.org; linux-arm-kernel@lists.infradead.org; linux-
> mmc@vger.kernel.org; linux-kernel@vger.kernel.org;
> devicetree@vger.kernel.org; mark.rutland@arm.com; robh+dt@kernel.org
> Cc: Anirudha Sarangi <anirudh@xilinx.com>; Srinivas Goud
> <sgoud@xilinx.com>
> Subject: Re: [RFC PATCH] mmc: sdhci-of-arasan: Add auto tuning support for
> ZynqMP Platform
>
> On 21/02/18 17:00, Manish Narani wrote:
> > Hi Adrian,
> >
> >> -----Original Message-----
> >> From: Manish Narani
> >> Sent: Wednesday, February 21, 2018 11:39 AM
> >> To: Adrian Hunter <adrian.hunter@intel.com>; michal.simek@xilinx.com;
> >> ulf.hansson@linaro.org; linux-arm-kernel@lists.infradead.org; linux-
> >> mmc@vger.kernel.org; linux-kernel@vger.kernel.org;
> >> devicetree@vger.kernel.org; mark.rutland@arm.com;
> robh+dt@kernel.org
> >> Cc: Anirudha Sarangi <anirudh@xilinx.com>; Srinivas Goud
> >> <sgoud@xilinx.com>
> >> Subject: RE: [RFC PATCH] mmc: sdhci-of-arasan: Add auto tuning
> >> support for ZynqMP Platform
> >>
> >> Hi Adrian,
> >>
> >>
> >>> -----Original Message-----
> >>> From: Adrian Hunter [mailto:adrian.hunter@intel.com]
> >>> Sent: Friday, February 16, 2018 7:37 PM
> >>> To: Manish Narani <MNARANI@xilinx.com>; michal.simek@xilinx.com;
> >>> ulf.hansson@linaro.org; linux-arm-kernel@lists.infradead.org; linux-
> >>> mmc@vger.kernel.org; linux-kernel@vger.kernel.org;
> >>> devicetree@vger.kernel.org; mark.rutland@arm.com;
> robh+dt@kernel.org
> >>> Cc: Anirudha Sarangi <anirudh@xilinx.com>; Srinivas Goud
> >>> <sgoud@xilinx.com>; Manish Narani <MNARANI@xilinx.com>
> >>> Subject: Re: [RFC PATCH] mmc: sdhci-of-arasan: Add auto tuning
> >>> support for ZynqMP Platform
> >>>
> >>> On 30/01/18 20:14, Manish Narani wrote:
> >>>> This patch adds support of SD auto tuning for ZynqMP platform. Auto
> >>>> tuning sequence sends tuning block to card when operating in UHS-1
> >>>> modes. This resets the DLL and sends CMD19/CMD21 as a part of the
> >>>> auto tuning process. Once the auto tuning process gets completed,
> >>>> reset the DLL to load the newly obtained SDHC tuned tap value.
> >>>
> >>> How is this different from:
> >>> 1. reset the dll
> >>> 2. call sdhci_execute_tuning
> >>> 3. reset the dll
> >>>
> > Below is my take on your above comments:
> > - 'Reset the dll' is a platform specific call inside
> > 'arasan_zynqmp_execute_tuning' which is implemented in
> > sdhci-of-arasan.c
> > - 'arasan_zynqmp_execute_tuning' is called from 'sdhci_execute_tuning'
> > as a platform_execute_tuning routine
> > - So to keep 'DLL reset' routine called from sdhci-of-arasan.c, I have
> > implemented the execute_tuning in sdhci-of-arasan.c
>
> I meant something like:
>
> if (of_device_is_compatible(pdev->dev.of_node, "xlnx,zynqmp-
> 8.9a"))
> host->mmc_host_ops.execute_tuning =
> arasan_zynqmp_execute_tuning;
>
This will need the removal of 'const' from 'static const struct mmc_host_ops sdhci_ops = {}' in sdhci.c file. Please confirm.

Thanks,
Manish
>
> static int arasan_zynqmp_execute_tuning(struct mmc_host *mmc, u32
> opcode) {
> struct sdhci_host *host = mmc_priv(mmc);
> struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> struct sdhci_arasan_data *sdhci_arasan =
> sdhci_pltfm_priv(pltfm_host);
> int err;
>
> arasan_zynqmp_dll_reset(host, sdhci_arasan->device_id);
>
> err = sdhci_execute_tuning(mmc, opcode);
> if (err)
> return err;
>
> arasan_zynqmp_dll_reset(host, sdhci_arasan->device_id);
>
> return 0;
> }
>
> >
> > Alternative way (Please review):
> > - Define a host->quirk2 bit (SDHCI_QUIRK2_DLL_RESET_NEEDED) in
> > sdhci-of-arasan.c indicating DLL reset needed while tuning operation
> > - Call 'dll reset' routine before and after __sdhci_execute_tuning()
> > in sdhci.c when a host->quirk2 bit (SDHCI_QUIRK2_DLL_RESET_NEEDED) is
> > set
>
> We should try to avoid quirks.
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