[U-Boot] [PATCH] mmd: sdhci: fix non GPIO card detect

[Baruch Siach]

Hi Faiz,

On Tue, Jul 23, 2019 at 03:35:31PM +0530, Faiz Abbas wrote:
> On 23/07/19 2:39 PM, Baruch Siach wrote:
> > On Tue, Jul 23, 2019 at 02:27:28PM +0530, Faiz Abbas wrote:
> >> On 23/07/19 1:30 PM, Peng Fan wrote:
> >>> + Faiz
> >>>
> >>>> Subject: [PATCH] mmd: sdhci: fix non GPIO card detect
> >>>>
> >>>> Some SD cards do not assert the SDHCI_CARD_PRESENT bit. Only the
> >>>> SDHCI_CARD_DETECT_PIN_LEVEL is enabled. Consider that enough for card
> >>>> detect indication.
> >>>>
> >>>> This fixes SD card access from SPL, since DM_GPIO is not available in SPL
> >>>> code.
> >>>>
> >>>> Fixes: da18c62b6e6a ("mmc: sdhci: Implement SDHCI card detect")
> >>>> Cc: T Karthik Reddy <t.karthik.reddy at xilinx.com>
> >>>> Cc: Michal Simek <michal.simek at xilinx.com>
> >>>> Signed-off-by: Baruch Siach <baruch at tkos.co.il>
> >>>> ---
> >>>>  drivers/mmc/sdhci.c | 2 +-
> >>>>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>>>
> >>>> diff --git a/drivers/mmc/sdhci.c b/drivers/mmc/sdhci.c index
> >>>> 2779bca93f08..17a28181fcca 100644
> >>>> --- a/drivers/mmc/sdhci.c
> >>>> +++ b/drivers/mmc/sdhci.c
> >>>> @@ -683,7 +683,7 @@ int sdhci_get_cd(struct udevice *dev)
> >>>>  	}
> >>>>  #endif
> >>>>  	value = !!(sdhci_readl(host, SDHCI_PRESENT_STATE) &
> >>>> -		   SDHCI_CARD_PRESENT);
> >>>> +		   (SDHCI_CARD_PRESENT | SDHCI_CARD_DETECT_PIN_LEVEL));
> >>>
> >>> Faiz, are you fine with this change?
> >>
> >> Not really. The spec is pretty clear that DETECT_PIN_LEVEL is not to be
> >> trusted. Also how does the CARD_PRESENT assertion depend on the SD card
> >> you use? Are you normally muxing the SDCD line to the IP (for hardware
> >> to detect) or are you connecting it as a gpio which software must detect?
> > 
> > I tested SanDisk 8GB SD card, class 10, UHS1, on Armada 388 based SolidRun 
> > Clearfog Base. The SDHCI_PRESENT_STATE register consistently reads 0x01f60000, 
> > that is, CARD_PRESENT is disabled, DETECT_PIN_LEVEL is enabled.
> > 
> > The SD card-detect GPIO is present at the hardware level, but it is not 
> > accessible from SPL code because there is currently no SPL_DM_GPIO. The main 
> > U-Boot image detects the SD card correctly (once the other MMC patches I 
> > posted are applied).
> > 
> > Without this patch boot from SD card is broken. What is the right fix then?
> 
> There are two choices to implement card detect:
> 
> 1. Mux the card detect line from the SD card cage directly to the host
> controller and expect PRESENT state register to indicate whether card is
> present or not.
> 
> 2. Mux the card detect line as a GPIO and use software
> (dm_gpio_get_value() call) to detect whether card is present or not. In
> that case, PRESENT_STATE[16,17,18] are completely useless because there
> is no card detect line going into the IP.
> 
> It seems that you are using #2. What confuses me is how any cards are
> able to assert CARD_DETECT.

As far as I can see the Armada 388 SD host controller does not provide option 
#1. The Clearfog indeed uses option #2. Until commit da18c62b6e6a4 ("mmc: 
sdhci: Implement SDHCI card detect") it used to work because the mv_sdhci 
driver does not implement the get_cd callback, so card-detect was ignored. Now 
we have a get_cd implementation at the sdhci level that returns 0 in SPL 
because the GPIO is not accessible.

What would you suggest?

baruch

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