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[209.85.166.178]) by smtp.gmail.com with ESMTPSA id z16sm123940iol.64.2019.10.16.17.22.21 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 16 Oct 2019 17:22:21 -0700 (PDT) Received: by mail-il1-f178.google.com with SMTP id c12so312664ilm.1 for ; Wed, 16 Oct 2019 17:22:21 -0700 (PDT) X-Received: by 2002:a92:819c:: with SMTP id q28mr703756ilk.269.1571271741101; Wed, 16 Oct 2019 17:22:21 -0700 (PDT) MIME-Version: 1.0 References: <20190722193939.125578-1-dianders@chromium.org> <20190722193939.125578-2-dianders@chromium.org> In-Reply-To: From: Doug Anderson Date: Wed, 16 Oct 2019 17:22:08 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2 1/2] mmc: core: Add sdio_trigger_replug() API To: Ulf Hansson Cc: Kalle Valo , Adrian Hunter , Ganapathi Bhat , linux-wireless , Andreas Fenkart , Brian Norris , Amitkumar Karwar , "open list:ARM/Rockchip SoC..." , Wolfram Sang , Nishant Sarmukadam , netdev , Avri Altman , "linux-mmc@vger.kernel.org" , "David S. Miller" , Xinming Hu , Matthias Kaehlcke , Linux Kernel Mailing List , Thomas Gleixner , Kate Stewart Content-Type: text/plain; charset="UTF-8" Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org Hi, On Thu, Oct 10, 2019 at 7:11 AM Ulf Hansson wrote: > > On Mon, 22 Jul 2019 at 21:41, Douglas Anderson wrote: > > > > When using Marvell WiFi SDIO cards, it is not uncommon for Linux WiFi > > driver to fully lose the communication channel to the firmware running > > on the card. Presumably the firmware on the card has a bug or two in > > it and occasionally crashes. > > > > The Marvell WiFi driver attempts to recover from this problem. > > Specifically the driver has the function mwifiex_sdio_card_reset() > > which is called when communcation problems are found. That function > > attempts to reset the state of things by utilizing the mmc_hw_reset() > > function. > > > > The current solution is a bit complex because the Marvell WiFi driver > > needs to manually deinit and reinit the WiFi driver around the reset > > call. This means it's going through a bunch of code paths that aren't > > normally tested. However, complexity isn't our only problem. The > > other (bigger) problem is that Marvell WiFi cards are often combo > > WiFi/Bluetooth cards and Bluetooth runs on a second SDIO func. While > > the WiFi driver knows that it should re-init its own state around the > > mmc_hw_reset() call there is no good way to inform the Bluetooth > > driver. That means that in Linux today when you reset the Marvell > > WiFi driver you lose all Bluetooth communication. Doh! > > Thanks for a nice description to the problem! > > In principle it makes mmc_hw_reset() quite questionable to use for > SDIO func drivers, at all. However, let's consider that for later. Yeah, unless you somehow knew that your card would only have one function. > > One way to fix the above problems is to leverage a more standard way > > to reset the Marvell WiFi card where we go through the same code paths > > as card unplug and the card plug. In this patch we introduce a new > > API call for doing just that: sdio_trigger_replug(). This API call > > will trigger an unplug of the SDIO card followed by a plug of the > > card. As part of this the card will be nicely reset. > > I have been thinking back and forth on this, exploring various > options, perhaps adding some callbacks that the core could invoke to > inform the SDIO func drivers of what is going on. > > Although, in the end this boils done to complexity and I think your > approach is simply the most superior in regards to this. However, I > think there is a few things that we can do to even further simply your > approach, let me comment on the code below. Right. Unplugging / re-plugging is sorta gross / inelegant, but it is definitely simpler and nice that it doesn't add so many new code paths. For cases where you're just trying to re-init things with a hammer it works pretty well. > > Signed-off-by: Douglas Anderson > > Reviewed-by: Matthias Kaehlcke > > --- > > > > Changes in v2: > > - s/routnine/routine (Brian Norris, Matthias Kaehlcke). > > - s/contining/containing (Matthias Kaehlcke). > > - Add Matthias Reviewed-by tag. > > > > drivers/mmc/core/core.c | 28 ++++++++++++++++++++++++++-- > > drivers/mmc/core/sdio_io.c | 20 ++++++++++++++++++++ > > include/linux/mmc/host.h | 15 ++++++++++++++- > > include/linux/mmc/sdio_func.h | 2 ++ > > 4 files changed, 62 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c > > index 221127324709..5da365b1fdb4 100644 > > --- a/drivers/mmc/core/core.c > > +++ b/drivers/mmc/core/core.c > > @@ -2161,6 +2161,12 @@ int mmc_sw_reset(struct mmc_host *host) > > } > > EXPORT_SYMBOL(mmc_sw_reset); > > > > +void mmc_trigger_replug(struct mmc_host *host) > > +{ > > + host->trigger_replug_state = MMC_REPLUG_STATE_UNPLUG; > > + _mmc_detect_change(host, 0, false); > > +} > > + > > static int mmc_rescan_try_freq(struct mmc_host *host, unsigned freq) > > { > > host->f_init = freq; > > @@ -2214,6 +2220,11 @@ int _mmc_detect_card_removed(struct mmc_host *host) > > if (!host->card || mmc_card_removed(host->card)) > > return 1; > > > > + if (host->trigger_replug_state == MMC_REPLUG_STATE_UNPLUG) { > > + mmc_card_set_removed(host->card); > > + return 1; > > Do you really need to set state of the card to "removed"? > > If I understand correctly, what you need is to allow mmc_rescan() to > run a second time, in particular for non removable cards. > > In that path, mmc_rescan should find the card being non-functional, > thus it should remove it and then try to re-initialize it again. Etc. > > Do you want me to send a patch to show you what I mean!? If you don't mind, that would probably be easiest. I've totally swapped out all of the implementation details of this from my brain now, but if I saw a patch from you it would be easy for me to analyze it and test it. Thanks! -Doug