linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Veerabhadrarao Badiganti <vbadigan@codeaurora.org>
To: Stephen Boyd <swboyd@chromium.org>, sbhanu@codeaurora.org
Cc: adrian.hunter@intel.com, robh+dt@kernel.org,
	ulf.hansson@linaro.org, asutoshd@codeaurora.org,
	stummala@codeaurora.org, rampraka@codeaurora.org,
	sayalil@codeaurora.org, sartgarg@codeaurora.org,
	rnayak@codeaurora.org, saiprakash.ranjan@codeaurora.org,
	sibis@codeaurora.org, cang@codeaurora.org,
	pragalla@codeaurora.org, nitirawa@codeaurora.org,
	linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org,
	agross@kernel.org, bjorn.andersson@linaro.org
Subject: Re: [PATCH V2] arm64: dts: qcom: sc7280: Add nodes for eMMC and SD card
Date: Thu, 25 Mar 2021 09:06:33 +0530	[thread overview]
Message-ID: <781df94a-b916-76eb-10c9-e95ba789f0b7@codeaurora.org> (raw)
In-Reply-To: <161660331135.3012082.15196616622122288364@swboyd.mtv.corp.google.com>


On 3/24/2021 9:58 PM, Stephen Boyd wrote:
> Quoting Stephen Boyd (2021-03-24 08:57:33)
>> Quoting sbhanu@codeaurora.org (2021-03-24 08:23:55)
>>> On 2021-03-23 12:31, Stephen Boyd wrote:
>>>> Quoting Shaik Sajida Bhanu (2021-03-20 11:17:00)
>>>>> +
>>>>> +                       bus-width = <8>;
>>>>> +                       non-removable;
>>>>> +                       supports-cqe;
>>>>> +                       no-sd;
>>>>> +                       no-sdio;
>>>>> +
>>>>> +                       max-frequency = <192000000>;
>>>> Is this necessary?
>>> yes, to avoid lower speed modes running with high clock rates.
>> Is it part of the DT binding? I don't see any mention of it.
> Nevermind, found it in mmc-controller.yaml. But I think this is to work
> around some problem with the clk driver picking lower speeds than
> requested? That has been fixed on the clk driver side (see commit like
> 148ddaa89d4a "clk: qcom: gcc-sc7180: Use floor ops for the correct sdcc1
> clk") so ideally this property can be omitted.
This is a good have dt node.

This will align clock requests between mmc core layer and sdhci-msm
platform driver. Say, for HS200/HS400 modes of eMMC, mmc-core layer
tries to set clock at 200Mhz, whereas sdhci-msm expects 192Mhz for
these modes. So we have to rely on clock driver floor/ceil values.
By having this property, mmc-core layer itself request for 192Mhz.

Same is for SD card SDR104 mode, core layer expects clock at 208Mhz
whereas sdhci-msm can max operate only at 202Mhz. By having this
property, core layer requests only for 202Mhz for SDR104 mode.

BTW, this helps only for max possible speed modes.
In case of lower-speed modes (for DDR52) we still need to rely on clock
floor rounding.


  reply	other threads:[~2021-03-25  3:37 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-20 18:17 [PATCH V2] arm64: dts: qcom: sc7280: Add nodes for eMMC and SD card Shaik Sajida Bhanu
2021-03-23  7:01 ` Stephen Boyd
2021-03-24 15:23   ` sbhanu
2021-03-24 15:57     ` Stephen Boyd
2021-03-24 16:28       ` Stephen Boyd
2021-03-25  3:36         ` Veerabhadrarao Badiganti [this message]
2021-03-25 16:20           ` Doug Anderson
2021-03-23 16:11 ` Doug Anderson
2021-03-25  3:58   ` Veerabhadrarao Badiganti
2021-03-25 16:17     ` Doug Anderson
2021-04-01  9:58       ` sbhanu
2021-03-26  6:56     ` sbhanu
2021-03-29 14:56       ` Doug Anderson
2021-04-13 10:59         ` sbhanu
2021-04-14 20:25           ` Doug Anderson
2021-04-16  9:52             ` Georgi Djakov
2021-04-20 17:20             ` sbhanu
2021-04-20 20:14               ` Doug Anderson
2021-04-28 10:47                 ` sbhanu
2021-04-28 15:13                   ` Doug Anderson
2021-04-29 20:44                     ` Georgi Djakov
2021-06-01  9:58                       ` sbhanu

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=781df94a-b916-76eb-10c9-e95ba789f0b7@codeaurora.org \
    --to=vbadigan@codeaurora.org \
    --cc=adrian.hunter@intel.com \
    --cc=agross@kernel.org \
    --cc=asutoshd@codeaurora.org \
    --cc=bjorn.andersson@linaro.org \
    --cc=cang@codeaurora.org \
    --cc=devicetree@vger.kernel.org \
    --cc=linux-arm-msm@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mmc@vger.kernel.org \
    --cc=nitirawa@codeaurora.org \
    --cc=pragalla@codeaurora.org \
    --cc=rampraka@codeaurora.org \
    --cc=rnayak@codeaurora.org \
    --cc=robh+dt@kernel.org \
    --cc=saiprakash.ranjan@codeaurora.org \
    --cc=sartgarg@codeaurora.org \
    --cc=sayalil@codeaurora.org \
    --cc=sbhanu@codeaurora.org \
    --cc=sibis@codeaurora.org \
    --cc=stummala@codeaurora.org \
    --cc=swboyd@chromium.org \
    --cc=ulf.hansson@linaro.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).