Re: [PATCH V2] arm64: dts: qcom: sc7280: Add nodes for eMMC and SD card

From: sbhanu@codeaurora.org
To: Doug Anderson <dianders@google.com>
Cc: Veerabhadrarao Badiganti <vbadigan@codeaurora.org>,
	Adrian Hunter <adrian.hunter@intel.com>,
	Ulf Hansson <ulf.hansson@linaro.org>,
	Rob Herring <robh+dt@kernel.org>,
	Asutosh Das <asutoshd@codeaurora.org>,
	Sahitya Tummala <stummala@codeaurora.org>,
	Ram Prakash Gupta <rampraka@codeaurora.org>,
	Sayali Lokhande <sayalil@codeaurora.org>,
	sartgarg@codeaurora.org, Rajendra Nayak <rnayak@codeaurora.org>,
	Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>,
	Sibi Sankar <sibis@codeaurora.org>,
	cang@codeaurora.org, pragalla@codeaurora.org,
	nitirawa@codeaurora.org,
	Linux MMC List <linux-mmc@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-arm-msm <linux-arm-msm@vger.kernel.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@vger.kernel.org>, Andy Gross <agross@kernel.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>
Subject: Re: [PATCH V2] arm64: dts: qcom: sc7280: Add nodes for eMMC and SD card
Date: Thu, 01 Apr 2021 15:28:34 +0530	[thread overview]
Message-ID: <f163ff1bcb870630ddcb963aa564a89e@codeaurora.org> (raw)
In-Reply-To: <CAD=FV=ULXU46C4jbx4nJEOuK4+wZmknoD=mZ_3=c0drfa32N=w@mail.gmail.com>

On 2021-03-25 21:47, Doug Anderson wrote:
> Hi,
> 
> On Wed, Mar 24, 2021 at 8:59 PM Veerabhadrarao Badiganti
> <vbadigan@codeaurora.org> wrote:
>> 
>> >> +                       clocks = <&gcc GCC_SDCC1_APPS_CLK>,
>> >> +                                       <&gcc GCC_SDCC1_AHB_CLK>,
>> >> +                                       <&rpmhcc RPMH_CXO_CLK>;
>> >> +                       clock-names = "core", "iface", "xo";
>> > I'm curious: why is the "xo" clock needed here but not for sc7180?
>> Actually its needed even for sc7180. We are making use of this clock 
>> in
>> msm_init_cm_dll()
>> The default PoR value is also same as calculated value for
>> HS200/HS400/SDR104 modes.
>> But just not to rely on default register values we need this entry.
> 
> Can you post a patch for sc7180?
sure will post a patch for sc7180.
> 
> 
>> >> +                       bus-width = <4>;
>> >> +
>> >> +                       no-mmc;
>> >> +                       no-sdio;
>> > Similar question to above: why exactly would mmc not work? Are you
>> > saying that if someone hooked this up to a full sized SD card slot and
>> > placed an MMC card into the slot that it wouldn't work? Similar
>> > question about SDIO. If someone placed an external SDIO card into your
>> > slot, would it not work?
>> >
>> As mentioned above, its just to optimize SDcard scan time a little.
> 
> OK. ...but while the eMMC one can make sense since the eMMC is
> soldered down (but in the board dts file, not in the SoC dtsi file) I
> think you should just remove these for SD card because:
> 
> 1. Even if only a uSD slot is exposed it's still _possible_ for
> someone to insert a card that uses MMC or SDIO signaling. If nothing
> else I have a (probably non-compliant) adapter that plugs into a uSD
> slot and provides a full sided SD slot. I could plug an MMC card or
> SDIO card in.
> 
> 2. Presumably the SD card scan time optimization is tiny.
> 
sure will remove these for SD card and will move eMMC flags(no-sd and 
no-sdio) to board dts file.
> 
> -Doug