Re: [PATCH V12 10/23] mmc: sdhci-uhs2: add reset function and uhs2_mode function

[Adrian Hunter <adrian.hunter@intel.com>]

On 3/10/23 15:22, Ulf Hansson wrote:
> On Tue, 3 Oct 2023 at 13:37, Adrian Hunter <adrian.hunter@intel.com> wrote:
>>
>> On 3/10/23 13:30, Ulf Hansson wrote:
>>> On Fri, 15 Sept 2023 at 11:44, Victor Shih <victorshihgli@gmail.com> wrote:
>>>>
>>>> From: Victor Shih <victor.shih@genesyslogic.com.tw>
>>>>
>>>> Sdhci_uhs2_reset() does a UHS-II specific reset operation.
>>>>
>>>> Signed-off-by: Ben Chuang <ben.chuang@genesyslogic.com.tw>
>>>> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
>>>> Signed-off-by: Victor Shih <victor.shih@genesyslogic.com.tw>
>>>> Acked-by: Adrian Hunter <adrian.hunter@intel.com>
>>>> ---
>>>>
>>>> Updates in V8:
>>>>  - Adjust the position of matching brackets.
>>>>
>>>> Updates in V6:
>>>>  - Remove unnecessary functions and simplify code.
>>>>
>>>> ---
>>>>
>>>>  drivers/mmc/host/sdhci-uhs2.c | 45 +++++++++++++++++++++++++++++++++++
>>>>  drivers/mmc/host/sdhci-uhs2.h |  2 ++
>>>>  2 files changed, 47 insertions(+)
>>>>
>>>> diff --git a/drivers/mmc/host/sdhci-uhs2.c b/drivers/mmc/host/sdhci-uhs2.c
>>>> index e339821d3504..dfc80a7f1bad 100644
>>>> --- a/drivers/mmc/host/sdhci-uhs2.c
>>>> +++ b/drivers/mmc/host/sdhci-uhs2.c
>>>> @@ -10,7 +10,9 @@
>>>>   *  Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
>>>>   */
>>>>
>>>> +#include <linux/delay.h>
>>>>  #include <linux/module.h>
>>>> +#include <linux/iopoll.h>
>>>>
>>>>  #include "sdhci.h"
>>>>  #include "sdhci-uhs2.h"
>>>> @@ -49,6 +51,49 @@ void sdhci_uhs2_dump_regs(struct sdhci_host *host)
>>>>  }
>>>>  EXPORT_SYMBOL_GPL(sdhci_uhs2_dump_regs);
>>>>
>>>> +/*****************************************************************************\
>>>> + *                                                                           *
>>>> + * Low level functions                                                       *
>>>> + *                                                                           *
>>>> +\*****************************************************************************/
>>>> +
>>>> +bool sdhci_uhs2_mode(struct sdhci_host *host)
>>>> +{
>>>> +       return host->mmc->flags & MMC_UHS2_SUPPORT;
>>>
>>> The MMC_UHS2_SUPPORT bit looks redundant to me. Instead, I think we
>>> should be using mmc->ios.timings, which already indicates whether we
>>> are using UHS2 (MMC_TIMING_UHS2_SPEED_*). See patch2 where we added
>>> this.
>>>
>>> That said, I think we should drop the sdhci_uhs2_mode() function
>>> altogether and instead use mmc_card_uhs2(), which means we should move
>>> it to include/linux/mmc/host.h, so it becomes available for host
>>> drivers.
>>>
>>
>> UHS2 mode starts at UHS2 initialization and ends either when UHS2
>> initialization fails, or the card is removed.
>>
>> So it includes re-initialization and reset when the transfer mode
>> currently transitions through MMC_TIMING_LEGACY.
>>
>> So mmc_card_uhs2() won't work correctly for the host callbacks
>> unless something is done about that.
> 
> Right, thanks for clarifying!
> 
> In that case I wonder if we couldn't change the way we update the
> ->ios.timing for UHS2. It seems silly to have two (similar) ways to
> indicate that we have moved to UHS2.

Perhaps something like below:

diff --git a/drivers/mmc/core/sd_uhs2.c b/drivers/mmc/core/sd_uhs2.c
index aacefdd6bc9e..e39d63d46041 100644
--- a/drivers/mmc/core/sd_uhs2.c
+++ b/drivers/mmc/core/sd_uhs2.c
@@ -70,7 +70,8 @@ static int sd_uhs2_power_off(struct mmc_host *host)
 
 	host->ios.vdd = 0;
 	host->ios.clock = 0;
-	host->ios.timing = MMC_TIMING_LEGACY;
+	/* Must set UHS2 timing to identify UHS2 mode */
+	host->ios.timing = MMC_TIMING_UHS2_SPEED_A;
 	host->ios.power_mode = MMC_POWER_OFF;
 	if (host->flags & MMC_UHS2_SD_TRAN)
 		host->flags &= ~MMC_UHS2_SD_TRAN;
@@ -1095,7 +1096,8 @@ static void sd_uhs2_detect(struct mmc_host *host)
 		mmc_claim_host(host);
 		mmc_detach_bus(host);
 		sd_uhs2_power_off(host);
-		host->flags &= ~MMC_UHS2_SUPPORT;
+		/* Remove UHS2 timing to indicate the end of UHS2 mode */
+		host->ios.timing = MMC_TIMING_LEGACY;
 		mmc_release_host(host);
 	}
 }
@@ -1338,7 +1340,8 @@ static int sd_uhs2_attach(struct mmc_host *host)
 err:
 	mmc_detach_bus(host);
 	sd_uhs2_power_off(host);
-	host->flags &= ~MMC_UHS2_SUPPORT;
+	/* Remove UHS2 timing to indicate the end of UHS2 mode */
+	host->ios.timing = MMC_TIMING_LEGACY;
 	return err;
 }
 
diff --git a/drivers/mmc/host/sdhci-uhs2.c b/drivers/mmc/host/sdhci-uhs2.c
index 517c497112f4..d1f3318b7d3a 100644
--- a/drivers/mmc/host/sdhci-uhs2.c
+++ b/drivers/mmc/host/sdhci-uhs2.c
@@ -267,10 +267,11 @@ static void __sdhci_uhs2_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
 
 	/* UHS2 timing. Note, UHS2 timing is disabled when powering off */
 	ctrl_2 = sdhci_readw(host, SDHCI_HOST_CONTROL2);
-	if (ios->timing == MMC_TIMING_UHS2_SPEED_A ||
-	    ios->timing == MMC_TIMING_UHS2_SPEED_A_HD ||
-	    ios->timing == MMC_TIMING_UHS2_SPEED_B ||
-	    ios->timing == MMC_TIMING_UHS2_SPEED_B_HD)
+	if (ios->power_mode != MMC_POWER_OFF &&
+	    (ios->timing == MMC_TIMING_UHS2_SPEED_A ||
+	     ios->timing == MMC_TIMING_UHS2_SPEED_A_HD ||
+	     ios->timing == MMC_TIMING_UHS2_SPEED_B ||
+	     ios->timing == MMC_TIMING_UHS2_SPEED_B_HD))
 		ctrl_2 |= SDHCI_CTRL_UHS2 | SDHCI_CTRL_UHS2_ENABLE;
 	else
 		ctrl_2 &= ~(SDHCI_CTRL_UHS2 | SDHCI_CTRL_UHS2_ENABLE);