From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vaibhav Hiremath Subject: Re: sdhci: runtime suspend/resume on card insert/removal Date: Mon, 14 Sep 2015 18:03:40 +0530 Message-ID: <55F6BEA4.1070803@linaro.org> References: <55F12CF8.50003@linaro.org> <20150910153129.07adbe68@xhacker> <20150910080233.GH21084@n2100.arm.linux.org.uk> <20150910160402.3b78b5c6@xhacker> <55F66874.2000609@linaro.org> <20150914142838.07ec6a07@xhacker> <55F681AC.2010605@linaro.org> <20150914161804.101dfc55@xhacker> <55F69121.3030700@linaro.org> <55F69E4F.8010608@linaro.org> <20150914105014.GJ21084@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-pa0-f52.google.com ([209.85.220.52]:36532 "EHLO mail-pa0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751285AbbINMdq (ORCPT ); Mon, 14 Sep 2015 08:33:46 -0400 Received: by padhk3 with SMTP id hk3so143304492pad.3 for ; Mon, 14 Sep 2015 05:33:45 -0700 (PDT) In-Reply-To: <20150914105014.GJ21084@n2100.arm.linux.org.uk> Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: Russell King - ARM Linux Cc: Jisheng Zhang , ulf.hansson@linaro.org, "linux-mmc@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , nico@fluxnic.net On Monday 14 September 2015 04:20 PM, 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, exactly. Its clock driver which is doing this. static struct mmp_param_gate_clk apmu_gate_clks[] = { /* The gate clocks has mux parent. */ {PXA1928_CLK_SDH0, "sdh0_clk", "sdh_div", CLK_SET_RATE_PARENT, PXA1928_CLK_SDH0 * 4, 0x1b, 0x1b, 0x0, 0, &sdh0_lock}, }; Here the mask and enable_val both are set to 0x1b, which means it shuts off both peripheral and AXI clock both. > 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. > Exactly, In my case, luckily I have eMMC on board, which keeps AXI clock ON all the time. Not sure why somebody would keep dependency like this, inspite having individual control for AXI clock. Thanks, Vaibhav From mboxrd@z Thu Jan 1 00:00:00 1970 From: vaibhav.hiremath@linaro.org (Vaibhav Hiremath) Date: Mon, 14 Sep 2015 18:03:40 +0530 Subject: sdhci: runtime suspend/resume on card insert/removal In-Reply-To: <20150914105014.GJ21084@n2100.arm.linux.org.uk> References: <55F12CF8.50003@linaro.org> <20150910153129.07adbe68@xhacker> <20150910080233.GH21084@n2100.arm.linux.org.uk> <20150910160402.3b78b5c6@xhacker> <55F66874.2000609@linaro.org> <20150914142838.07ec6a07@xhacker> <55F681AC.2010605@linaro.org> <20150914161804.101dfc55@xhacker> <55F69121.3030700@linaro.org> <55F69E4F.8010608@linaro.org> <20150914105014.GJ21084@n2100.arm.linux.org.uk> Message-ID: <55F6BEA4.1070803@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Monday 14 September 2015 04:20 PM, 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, exactly. Its clock driver which is doing this. static struct mmp_param_gate_clk apmu_gate_clks[] = { /* The gate clocks has mux parent. */ {PXA1928_CLK_SDH0, "sdh0_clk", "sdh_div", CLK_SET_RATE_PARENT, PXA1928_CLK_SDH0 * 4, 0x1b, 0x1b, 0x0, 0, &sdh0_lock}, }; Here the mask and enable_val both are set to 0x1b, which means it shuts off both peripheral and AXI clock both. > 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. > Exactly, In my case, luckily I have eMMC on board, which keeps AXI clock ON all the time. Not sure why somebody would keep dependency like this, inspite having individual control for AXI clock. Thanks, Vaibhav