Re: [v6, 5/5] mmc: sdhci-of-esdhc: fix host version for T4240-R1.0-R2.0

[Scott Wood]

On 03/14/2016 02:29 AM, Yangbo Lu wrote:
>> -----Original Message-----
>> From: Arnd Bergmann [mailto:arnd@xxxxxxxx]
>> Sent: Monday, March 14, 2016 6:26 AM
>> To: linuxppc-dev@xxxxxxxxxxxxxxxx
>> Cc: Yangbo Lu; devicetree@xxxxxxxxxxxxxxx; linux-arm-
>> kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-
>> clk@xxxxxxxxxxxxxxx; linux-i2c@xxxxxxxxxxxxxxx; iommu@xxxxxxxxxxxx
>> foundation.org; netdev@xxxxxxxxxxxxxxx; linux-mmc@xxxxxxxxxxxxxxx;
>> ulf.hansson@xxxxxxxxxx; Zhao Qiang; Russell King; Bhupesh Sharma; Joerg
>> Roedel; Santosh Shilimkar; Scott Wood; Rob Herring; Claudiu Manoil; Kumar
>> Gala; Yang-Leo Li; Xiaobo Xie
>> Subject: Re: [v6, 5/5] mmc: sdhci-of-esdhc: fix host version for T4240-
>> R1.0-R2.0
>>
>> On Wednesday 09 March 2016 18:08:51 Yangbo Lu wrote:
>>> @@ -567,10 +580,20 @@ static void esdhc_init(struct platform_device
>> *pdev, struct sdhci_host *host)
>>>         struct sdhci_pltfm_host *pltfm_host;
>>>         struct sdhci_esdhc *esdhc;
>>>         u16 host_ver;
>>> +       u32 svr;
>>>
>>>         pltfm_host = sdhci_priv(host);
>>>         esdhc = sdhci_pltfm_priv(pltfm_host);
>>>
>>> +       fsl_guts_init();
>>> +       svr = fsl_guts_get_svr();
>>> +       if (svr) {
>>> +               esdhc->soc_ver = SVR_SOC_VER(svr);
>>> +               esdhc->soc_rev = SVR_REV(svr);
>>> +       } else {
>>> +               dev_err(&pdev->dev, "Failed to get SVR value!\n");
>>> +       }
>>> +
>>
>> This makes the driver non-portable. Better identify the specific
>> workarounds based on the compatible string for this device, or add a
>> boolean DT property for the quirk.
>>
>> 	Arnd
> 
> [Lu Yangbo-B47093] Hi Arnd, we did have a discussion about using DTS in v1 before.
> https://patchwork.kernel.org/patch/6834221/
> 
> We don’t have a separate DTS file for each revision of an SOC and if we did, we'd constantly have people using the wrong one.
> In addition, the device tree is stable ABI and errata are often discovered after device tree are deployed.
> See the link for details.
> 
> So we decide to read SVR from the device-config/guts MMIO block other than using DTS.
> Thanks.

Also note that this driver is already only for fsl-specific hardware,
and it will still work even if fsl_guts doesn't find anything to bind to
-- it just wouldn't be able to detect errata based on SVR in that case.

-Scott