Path: csiph.com!news.mixmin.net!news.unit0.net!news.panservice.it!bofh.it!news.nic.it!robomod From: Romain Perier Newsgroups: linux.kernel Subject: Re: [PATCH] mmc: core: Fix power sequence ordering in mmc_power_up Date: Wed, 01 Mar 2017 11:20:02 +0100 Message-ID: References: User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 MIME-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Sender: robomod@news.nic.it List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Approved: robomod@news.nic.it Lines: 84 Organization: linux.* mail to news gateway X-Original-Cc: linux-mmc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Sjoerd Simons X-Original-Date: Wed, 1 Mar 2017 11:00:12 +0100 X-Original-Message-ID: <44646f74-6260-6c0e-3726-60f90fd57149@collabora.com> X-Original-References: <20170301085902.7388-1-romain.perier@collabora.com> X-Original-Sender: linux-kernel-owner@vger.kernel.org Xref: csiph.com linux.kernel:1590181 Hi, Le 01/03/2017 à 10:53, Arend Van Spriel a écrit : > On 1-3-2017 9:59, Romain Perier wrote: >> Currently, mmc_power_up calls the pre_power_on callback, enables the >> power supply of the mmc by calling mmc_set_ios() and then call >> post_power_on. WiFi chipsets like the AP6335 require a specific power >> sequence ordering before being used. You must enable the power supply >> and wait until it reaches its minimum voltage, gate the clock and wait >> at least two cycles and then assert the reset line. > Hi Romain, > > You have to be more clear. What power supply, ie. vmmc or the supply for > the wifi chipset. Without knowing much of the details to me this sounds > like a new powerseq variant. That's for vqmmc. vqmmc has to be power on, then the clock must be enabled and then the reset line must be toggled. > >> This commit prevents regulators to be enabled in the middle of or after >> the power sequencing. We this fix, mmc_set_ios is first call, the >> underlying regulators are enabled, then pre_power_on and post_power_on >> are called, so clock and reset line are enabled in the right order, >> after the regulator. > It feels counter intuitive and maybe even wrong to change a setup > pattern like this. Can you be sure this will not cause any regressions? Well, I could keep the current pattern as it was currently working, and propose another one for this case (as an RFC). What do you think ? Regards, Romain > > Regards, > Arend > >> Signed-off-by: Romain Perier >> --- >> drivers/mmc/core/core.c | 13 +++++++++---- >> 1 file changed, 9 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c >> index 1076b9d..36df24f 100644 >> --- a/drivers/mmc/core/core.c >> +++ b/drivers/mmc/core/core.c >> @@ -1798,8 +1798,6 @@ void mmc_power_up(struct mmc_host *host, u32 ocr) >> if (host->ios.power_mode == MMC_POWER_ON) >> return; >> >> - mmc_pwrseq_pre_power_on(host); >> - >> host->ios.vdd = fls(ocr) - 1; >> host->ios.power_mode = MMC_POWER_UP; >> /* Set initial state and call mmc_set_ios */ >> @@ -1819,13 +1817,20 @@ void mmc_power_up(struct mmc_host *host, u32 ocr) >> */ >> mmc_delay(10); >> >> - mmc_pwrseq_post_power_on(host); >> - >> host->ios.clock = host->f_init; >> >> host->ios.power_mode = MMC_POWER_ON; >> mmc_set_ios(host); >> >> + mmc_pwrseq_pre_power_on(host); >> + >> + /* >> + * This delay should be sufficient to wait at least two cycles of clock >> + * gated by pre_power_on >> + */ >> + mmc_delay(1); >> + mmc_pwrseq_post_power_on(host); >> + >> /* >> * This delay must be at least 74 clock sizes, or 1 ms, or the >> * time required to reach a stable voltage. >>