On Wed, Sep 05, 2018 at 09:45:15PM +0200, Cedric Roux wrote: > On 09/05/2018 07:45 PM, Krzysztof Kozlowski wrote: > > I looked at Mini2440 schematics found on the net and it looks like the > > pin (just like CD) is active low. However I might be looking at wrong > > schematics or missing some things. > > I have the same schematics I think. > But I have a real mini2440 and I am positively sure that WP > is active high. CD is active low, yes. > > Do you know someone that you trust that could confirm this? > > > > > This is really an old code so I am just quite surprised that it was not > > reported before. Not able to write to SD card (for example if it is > > rootfs) should be spotted quite early. > > I don't think anyone tried a recent kernel, that's why. > And the mini2440 has been kind of replaced by the mini6410, > I'm not sure it's still in production. Apart from me, I > don't think anyone still uses it. If someone does, I > heavily doubt that person will try to boot a 4.something > kernel on it. > > In the 2.6.32.63 kernel it's all different. > > We have s3cmci_get_ro in drivers/mmc/host/s3cmci.c > that calls s3c2410_gpio_getpin in arch/arm/plat-s3c24xx/gpio.c > that returns the WP bit as is read from the GPIO. > s3cmci_get_ro will return > 0 if the bit is set and > wprotect_invert is not set. For mini2440, wprotect_invert > is not set (actually it does not seem to be set anywhere > in the kernel tree, is it used at all in 2.6.32.63?). So > it's returned as is. Getting 1 from GPIO means Read Only. > > Then we have s3cmci_card_present, also in drivers/mmc/host/s3cmci.c, > that reads the CD bit from the GPIO, but take the opposite value > and then returns the opposite of the result if detect_invert > is 1. For mini2440 it's not 1, but 0. So we return the opposite > of the CD bit read from the GPIO, which means active low. > > I'm not an electronic professional so I don't know how to interpret > the schematics. My experiment with my mini2440 says that: > - no card: WP bit = 1, CD bit = 1 > - card read/write: WP bit = 0, CD bit = 0 > - card read only: WP bit = 1, CD bit = 0 > By "WP bit" I mean the value read from GPH8. > By "CD bit" I mean the value read from GPG8. > > So I don't know what to do. If you don't trust me and you know > no one that you trust that would confirm my findings, then it's > game over. > > I can do things that you ask me to do to prove my claims. > > I can provide a simple userland program to be run on a mini2440 > that demonstrates this as well (open /dev/mem, mmap 0x56000000, > reads GPG and GPH and prints the values). You provided really good explanation so let's go with your patch. Thanks, applied. Best regards, Krzysztof
