Re: [PATCH v2 2/4] mmc: core: group default initial state

Johan Rudholm
2014-11-05T12:22:08Z

Hi Ulf,

2014-11-05 11:13 GMT+01:00 Ulf Hansson <ulf.hansson@linaro.org>:
> On 4 November 2014 16:07, Johan Rudholm <johan.rudholm@axis.com> wrote:
>> mmc_do_hw_reset, mmc_power_up and mmc_power_off all set the same
>> group of initial values, simplify by sticking them together.
>
> That's not entirely true. This patch will actually change the
> behaviour for the "ios.bus_mode", which isn't exactly what the commit
> message are telling us. See more below.
>
> I still think this patch is interesting, since apparently the value of
> "ios.bus_mode" hasn't been handled consistently. In principle I like
> the approach of this patch, but we need to make sure it's working and
> following the specs.

Thank you for pointing this out. I've double-checked the JEDEC 5.01
spec regarding the bus mode in the context of this initial state, see
below for comments.

>
> Kind regards
> Uffe
>
>>
>> Signed-off-by: Johan Rudholm <johanru@axis.com>
>> ---
>> drivers/mmc/core/core.c | 49 +++++++++++++++++++++++------------------------
>> drivers/mmc/core/core.h | 1 +
>> 2 files changed, 25 insertions(+), 25 deletions(-)
>>
>> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
>> index 5d215ee..2c39d26 100644
>> --- a/drivers/mmc/core/core.c
>> +++ b/drivers/mmc/core/core.c
>> @@ -1088,6 +1088,24 @@ void mmc_set_bus_width(struct mmc_host *host, unsigned int width)
>> mmc_host_clk_release(host);
>> }
>>
>> +/*
>> + * Set initial state after a power cycle or a hw_reset.
>> + */
>> +void mmc_set_initial_state(struct mmc_host *host)
>> +{
>> + if (mmc_host_is_spi(host)) {
>> + host->ios.chip_select = MMC_CS_HIGH;
>> + host->ios.bus_mode = MMC_BUSMODE_PUSHPULL;
>> + } else {
>> + host->ios.chip_select = MMC_CS_DONTCARE;
>> + host->ios.bus_mode = MMC_BUSMODE_OPENDRAIN;
>> + }
>> + host->ios.bus_width = MMC_BUS_WIDTH_1;
>> + host->ios.timing = MMC_TIMING_LEGACY;
>> +
>> + mmc_set_ios(host);
>> +}
>> +
>> /**
>> * mmc_vdd_to_ocrbitnum - Convert a voltage to the OCR bit number
>> * @vdd: voltage (mV)
>> @@ -1534,15 +1552,9 @@ void mmc_power_up(struct mmc_host *host, u32 ocr)
>> mmc_host_clk_hold(host);
>>
>> host->ios.vdd = fls(ocr) - 1;
>> - if (mmc_host_is_spi(host))
>> - host->ios.chip_select = MMC_CS_HIGH;
>> - else
>> - host->ios.chip_select = MMC_CS_DONTCARE;
>> - host->ios.bus_mode = MMC_BUSMODE_PUSHPULL;
>
> Earlier we used always used MMC_BUSMODE_PUSHPULL, now it will depend on "spi".

The JEDEC spec says that in device identification mode the bus should
be open-drain and not push-pull. So this way should be compliant to
the spec, right? Unfortunately, I will require help in testing this on
a proper eMMC.

I can't find anything in the JEDEC or the SD spec about bus mode in
SPI mode though. However, this behavior is not changed by this patch,
so we should be safe.

>> host->ios.power_mode = MMC_POWER_UP;
>> - host->ios.bus_width = MMC_BUS_WIDTH_1;
>> - host->ios.timing = MMC_TIMING_LEGACY;
>> - mmc_set_ios(host);
>> + /* Set initial state and call mmc_set_ios */
>> + mmc_set_initial_state(host);
>>
>> /* Try to set signal voltage to 3.3V but fall back to 1.8v or 1.2v */
>> if (__mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_330) == 0)
>> @@ -1582,14 +1594,9 @@ void mmc_power_off(struct mmc_host *host)
>> host->ios.clock = 0;
>> host->ios.vdd = 0;
>>
>> - if (!mmc_host_is_spi(host)) {
>> - host->ios.bus_mode = MMC_BUSMODE_OPENDRAIN;
>> - host->ios.chip_select = MMC_CS_DONTCARE;
>
> So in here another change in behaviour, right!?

Ok, so the behavior for SPI is changed in this case, now we explicitly
set the bus+cs modes and before we left them as they were.

Does this matter though, since we're powering off the device and the
bus+cs modes will be set on the subsequent mmc_power_up?

>
>> - }
>> host->ios.power_mode = MMC_POWER_OFF;
>> - host->ios.bus_width = MMC_BUS_WIDTH_1;
>> - host->ios.timing = MMC_TIMING_LEGACY;
>> - mmc_set_ios(host);
>> + /* Set initial state and call mmc_set_ios */
>> + mmc_set_initial_state(host);
>>
>> /*
>> * Some configurations, such as the 802.11 SDIO card in the OLPC
>> @@ -2273,16 +2280,8 @@ static int mmc_do_hw_reset(struct mmc_host *host, int check)
>> }
>> }
>>
>> - if (mmc_host_is_spi(host)) {
>> - host->ios.chip_select = MMC_CS_HIGH;
>> - host->ios.bus_mode = MMC_BUSMODE_PUSHPULL;
>> - } else {
>> - host->ios.chip_select = MMC_CS_DONTCARE;
>> - host->ios.bus_mode = MMC_BUSMODE_OPENDRAIN;
>> - }
>> - host->ios.bus_width = MMC_BUS_WIDTH_1;
>> - host->ios.timing = MMC_TIMING_LEGACY;
>> - mmc_set_ios(host);
>> + /* Set initial state and call mmc_set_ios */
>> + mmc_set_initial_state(host);
>>
>> mmc_host_clk_release(host);
>>
>> diff --git a/drivers/mmc/core/core.h b/drivers/mmc/core/core.h
>> index 443a584..d76597c 100644
>> --- a/drivers/mmc/core/core.h
>> +++ b/drivers/mmc/core/core.h
>> @@ -49,6 +49,7 @@ void mmc_set_driver_type(struct mmc_host *host, unsigned int drv_type);
>> void mmc_power_up(struct mmc_host *host, u32 ocr);
>> void mmc_power_off(struct mmc_host *host);
>> void mmc_power_cycle(struct mmc_host *host, u32 ocr);
>> +void mmc_set_initial_state(struct mmc_host *host);
>>
>> static inline void mmc_delay(unsigned int ms)
>> {
>> --
>> 1.7.2.5
>>
>
> Kind regards
> Uffe

//Johan