linux-kernel - Re: [PATCH] mmc: enable UHS voltage switch for SDSC if supported【请注意，邮件由linux-mmc-owner@...r.kernel.org代发】

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Date:   Fri, 23 Apr 2021 14:51:26 +0800
From:   Shawn Lin <shawn.lin@...k-chips.com>
To:     Christian Löhle <CLoehle@...erstone.com>
Cc:     shawn.lin@...k-chips.com, "pali@...nel.org" <pali@...nel.org>,
        "huyue2@...ong.com" <huyue2@...ong.com>,
        "tiantao6@...ilicon.com" <tiantao6@...ilicon.com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "ulf.hansson@...aro.org" <ulf.hansson@...aro.org>
Subject: Re: [PATCH] mmc: enable UHS voltage switch for SDSC if supported【请注意，邮件由linux-mmc-owner@...r.kernel.org代发】

On 2021/4/23 14:38, Christian Löhle wrote:
> Claiming UHS-I support with SDSC is pretty rare, for obvious reasons (namely they are non-standard, so it's a gamble if a host makes use of it), but here you go:
> https://de.rs-online.com/web/p/micro-sd-karten/8743910/
> (sorry for the german, the site has a en. subpage, but it's certificate seem untrusted.)
> The more likely case is that they do not advertise UHS-I to customers,
> but the card will show support to the host.
> Let's look at this product, just as an example.
> https://www.tme.eu/html/EN/goodram-industrial-industrial-sd-sd-micro-memory-cards/ramka_15242_EN_pelny.html
> They provide an MLC and pSLC version of each device, with half the capacity naturally.
> The 4GB MLC claims UHS-I support, the 2GB pSLC is very likely to be the same controller,
> it only claims Class 6.
> So either they specifically changed the firmware to remove any UHS support indication,
> or, more likely IMO, the card still reports UHS support to the host.
> Such a card would benefit from this patch.
> 
> Disclaimer: I do not own the product and have not confirmed this device in any way,
> but I have seen UHS support on other devices that do not advertise it for their
> SDSC versions.
> If the mailing list would be interested, I can try to acquire such devices, listed in
> public open stores. Modern, potentially UHS supporting cards. are,
> as mentioned in the initial Mail, often SLC or pSLC and often are made on
> a customers request.
> 
> 

Thanks for sharing these, but from the datasheets, these SDSC cards
claims their throught up to 20MB/s. So, I guess highpseed mode is enough
for them? what do you think?

> From: Shawn Lin <shawn.lin@...k-chips.com>
> Sent: Friday, April 23, 2021 3:34 AM
> To: Christian Löhle <CLoehle@...erstone.com>
> Cc: shawn.lin@...k-chips.com <shawn.lin@...k-chips.com>; pali@...nel.org <pali@...nel.org>; huyue2@...ong.com <huyue2@...ong.com>; tiantao6@...ilicon.com <tiantao6@...ilicon.com>; linux-mmc@...r.kernel.org <linux-mmc@...r.kernel.org>; linux-kernel@...r.kernel.org <linux-kernel@...r.kernel.org>; ulf.hansson@...aro.org <ulf.hansson@...aro.org>
> Subject: Re: [PATCH] mmc: enable UHS voltage switch for SDSC if supported【请注意，邮件由linux-mmc-owner@...r.kernel.org代发】
>   
> On 2021/4/22 21:18, Christian Löhle wrote:
>> Ignore the reported capacity if the card otherwise reports UHS support.
>>
>> Currently SDSC cards reporting UHS support except for the CCS do not run
>> through the voltage switch.
>> While strictly speaking a SDSC card cannot support UHS in compliance
>> with the standard, there is no good reason to throttle them that way.
>> Especially for pSLCs in practice such cards benefit greatly by this patch,
> 
> Cduld you provide some more infomation about the SDSC cards which ones
> are labeled as UHS, e.g brand, webpage....
> 
>> as they can be new and UHS supporting, but must not lie about their CCS.
>> The behaviour of linux-mmc for SDSC is deviating from the standard anyway
>> in such a case, as the card is treated as UHS card not supporting the
>> voltage switch in general.
>> Such a card will come up as
>> mmc0: new ultra high speed SDR25 SD card at address 0001.
>> Thus the subsystem will support CMD23 and others to the card.
>> But if we deviate from the standard anyway, then we might as well
>> not throttle SDSC to 25MB/s.
>>
>> Signed-off-by: Christian Loehle <cloehle@...erstone.com>
>> ---
>>     drivers/mmc/core/sd.c | 7 +++----
>>     1 file changed, 3 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
>> index 6fa51a6ed058..281ca2da8e0b 100644
>> --- a/drivers/mmc/core/sd.c
>> +++ b/drivers/mmc/core/sd.c
>> @@ -841,11 +841,10 @@ int mmc_sd_get_cid(struct mmc_host *host, u32 ocr, u32 *cid, u32 *rocr)
>>                  return err;
>>     
>>          /*
>> -      * In case CCS and S18A in the response is set, start Signal Voltage
>> -      * Switch procedure. SPI mode doesn't support CMD11.
>> +      * In case S18A in the response is set, start Signal Voltage Switch
>> +      * procedure. SPI mode doesn't support CMD11.
>>           */
>> -     if (!mmc_host_is_spi(host) && rocr &&
>> -        ((*rocr & 0x41000000) == 0x41000000)) {
>> +     if (!mmc_host_is_spi(host) && rocr && (*rocr & 0x01000000)) {
>>                  err = mmc_set_uhs_voltage(host, pocr);
>>                  if (err == -EAGAIN) {
>>                          retries--;
>>
> 
> 
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