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[120.74.102.185]) by smtp.gmail.com with ESMTPSA id f28sm9137653pfq.191.2020.09.13.23.40.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 13 Sep 2020 23:40:05 -0700 (PDT) Date: Mon, 14 Sep 2020 15:40:01 +0900 From: AKASHI Takahiro To: Adrian Hunter Cc: Ben Chuang , ulf.hansson@linaro.org, linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org, ben.chuang@genesyslogic.com.tw, greg.tu@genesyslogic.com.tw Subject: Re: [RFC PATCH V3 13/21] mmc: sdhci: UHS-II support, skip signal_voltage_switch() Message-ID: <20200914064001.GA2743583@laputa> Mail-Followup-To: AKASHI Takahiro , Adrian Hunter , Ben Chuang , ulf.hansson@linaro.org, linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org, ben.chuang@genesyslogic.com.tw, greg.tu@genesyslogic.com.tw References: <20200710111104.29616-1-benchuanggli@gmail.com> <9ab64a9d-cd78-785c-b48f-561048cfe2ed@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9ab64a9d-cd78-785c-b48f-561048cfe2ed@intel.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Adrian, On Fri, Aug 21, 2020 at 05:09:01PM +0300, Adrian Hunter wrote: > On 10/07/20 2:11 pm, Ben Chuang wrote: > > From: AKASHI Takahiro > > > > sdhci_start_signal_voltage_switch() should be called only in UHS-I mode, > > and not for UHS-II mode. > > > > Signed-off-by: Ben Chuang > > Signed-off-by: AKASHI Takahiro > > --- > > drivers/mmc/host/sdhci.c | 7 ++++++- > > 1 file changed, 6 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c > > index 5511649946b9..7f2537648a08 100644 > > --- a/drivers/mmc/host/sdhci.c > > +++ b/drivers/mmc/host/sdhci.c > > @@ -2623,8 +2623,13 @@ int sdhci_start_signal_voltage_switch(struct mmc_host *mmc, > > /* > > * Signal Voltage Switching is only applicable for Host Controllers > > * v3.00 and above. > > + * But for UHS2, the signal voltage is supplied by vdd2 which is > > + * already 1.8v so no voltage switch required. > > */ > > - if (host->version < SDHCI_SPEC_300) > > + if (host->version < SDHCI_SPEC_300 || > > + (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) && > > + host->version >= SDHCI_SPEC_400 && > > + host->mmc->flags & MMC_UHS2_SUPPORT)) > > Please look at hooking ->start_signal_voltage_switch() instead Do you mean that you want every platform driver who wants to support UHS-II to set NULL to start_signal_voltage_switch hook even if this hack is platform agnostic? (Another option is that it would be put in sdhci_uhs2_add_host() which is responsible to set MMC_UHS2_SUPPORT.) -Takahiro Akashi > > > > return 0; > > > > ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2); > > >