On Mon, Sep 14, 2015 at 11:50:14AM +0100, Russell King - ARM Linux wrote: > On Mon, Sep 14, 2015 at 03:45:43PM +0530, Vaibhav Hiremath wrote: > > Came across below lines in the datasheet, > > > > ========= Copy-n-paste from datasheet============ > > > > All SDH interfaces share the same clock which is enabled when any of the SDH > > clock enables are > > set (from PMUA_SDH1_CLK_RES_CTRL, PMUA_SDH2_CLK_RES_CTRL, > > PMUA_SDH3_CLK_RES_CTRL, PMUA_SDH4_CLK_RES_CTRL, > > PMUA_SDH5_CLK_RES_CTRL), with clock source select and divider ratio > > controlled by > > PMUA_SDH1_CLK_RES_CTRL. > > > > ================================================== > > > > > > And I can confirm that after disabling AXI interface clock for all the > > SDH modules (1-5) I see I get an abort. > > > > This clearly explains/justifies/proves that the existing code is > > working as expected. I have eMMC mounted on the board, which makes > > clock to always stay ON on SDH3. > > > > So there is an OR gate implemented inside which takes input from > > SDHx_AXI_EN and feeds back to all SDHx instances. Don't ask me why it > > has been designed that way :) > > > > And I did some experiment as well, so what I have observed is, > > SDH_AXI_CLOCK is required to generate card detection, without that I do > > not see card detection working. > > What that means is that if DT configures the interface to use its > internal card detection, the AXI clock must never shut off when entering > runtime-PM. > > Yes, it means you don't get the same savings as you would by turning > off that clock, but that's the choice between using the internal card > detection and a GPIO for this. The code shouldn't force you to use a > GPIO just because the Linux driver implementation dumbly disables the > AXI clock. Note that should also happen if a SDIO card is inserted, and the SDIO IRQ is enabled - so the SDIO card can signal an interrupt back to the host. -- FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
