linux-kernel - Re: [PATCH V1] mmc: sdhci-msm: Enable MMC_CAP_AGGRESSIVE

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Message-ID: <tpervpypkne6lasl3fn3v52xutl3zfuytalo3cveoe4us63rrb@p2w4cvt2jf7a>
Date: Thu, 24 Jul 2025 15:01:01 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Sarthak Garg <quic_sartgarg@...cinc.com>
Cc: Adrian Hunter <adrian.hunter@...el.com>,
        Ulf Hansson <ulf.hansson@...aro.org>, linux-mmc@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        quic_cang@...cinc.com, quic_nguyenb@...cinc.com,
        quic_rampraka@...cinc.com, quic_pragalla@...cinc.com,
        quic_sayalil@...cinc.com, quic_nitirawa@...cinc.com,
        quic_bhaskarv@...cinc.com, kernel@...cinc.com
Subject: Re: [PATCH V1] mmc: sdhci-msm: Enable MMC_CAP_AGGRESSIVE_PM for
 qualcomm controllers

On Thu, Jul 24, 2025 at 04:45:38PM +0530, Sarthak Garg wrote:
> 
> 
> On 5/21/2025 9:11 PM, Dmitry Baryshkov wrote:
> > On 21/05/2025 18:36, Sarthak Garg wrote:
> > > 
> > > 
> > > On 5/21/2025 8:19 PM, Dmitry Baryshkov wrote:
> > > > On 21/05/2025 17:35, Sarthak Garg wrote:
> > > > > 
> > > > > 
> > > > > On 5/21/2025 6:25 PM, Dmitry Baryshkov wrote:
> > > > > > On Wed, May 21, 2025 at 12:46:49PM +0530, Sarthak Garg wrote:
> > > > > > > 
> > > > > > > 
> > > > > > > On 11/15/2024 6:53 PM, Dmitry Baryshkov wrote:
> > > > > > > > On Fri, 15 Nov 2024 at 12:23, Sarthak Garg
> > > > > > > > <quic_sartgarg@...cinc.com> wrote:
> > > > > > > > > 
> > > > > > > > > 
> > > > > > > > > 
> > > > > > > > > On 11/4/2024 4:19 PM, Dmitry Baryshkov wrote:
> > > > > > > > > > On Mon, Nov 04, 2024 at 11:37:22AM +0530, Sarthak Garg wrote:
> > > > > > > > > > > Enable MMC_CAP_AGGRESSIVE_PM for qualcomm controllers.
> > > > > > > > > > > This enables runtime PM for eMMC/SD card.
> > > > > > > > > > 
> > > > > > > > > > Could you please mention, which
> > > > > > > > > > platforms were tested with this patch?
> > > > > > > > > > Note, upstream kernel supports a lot of
> > > > > > > > > > platforms, including MSM8974, I
> > > > > > > > > > think the oldest one, which uses SDHCI.
> > > > > > > > > > 
> > > > > > > > > 
> > > > > > > > > This was tested with qdu1000 platform.
> > > > > > > > 
> > > > > > > > Are you sure that it won't break other platforms?
> > > > > > > > 
> > > > > > > 
> > > > > > > Thanks for your valuable comment.
> > > > > > > I am not sure about the older platforms so to avoid issues on older
> > > > > > > platforms we can enable this for all SDCC version 5.0 targets ?
> > > > > > 
> > > > > > No, there are still a lot of platforms. Either explain why this is
> > > > > > required for all v5 platforms (and won't break those) or
> > > > > > find some other
> > > > > > way, e.g. limit the change to QDU1000, explaining why it is _not_
> > > > > > applicable to other platforms.
> > > > > > 
> > > > > 
> > > > > Thanks for your comment.
> > > > 
> > > > No need to.
> > > >  >> I agree with your concern but for me also its not possible
> > > > to test on
> > > > > all the platforms.
> > > > 
> > > > Sure.
> > > > >> Lets say if I want to enable this caps for QDU1000 for which it has
> > > > > been tested and on any other upcoming target after testing,
> > > > > then how can I proceed to enable?
> > > > 
> > > > Let's start from the beginning: why do you want to enable it on QDU1000?
> > > > 
> > > 
> > > QDU1000 is one latest available target where we have enabled this
> > > and tested. This has been enabled to save power.
> > 
> > Isn't it a powered device? How much power is the save? Is it worth it?
> > 
> 
> Sorry I just did basic sanity on QDU1000 device to confirm its not breaking
> any eMMC functionality and we have also tested SD card on SM8550 as well.
> For power no's we have stared internal discussions and based on target
> available for power profiling with eMMC device we will come back.

So, again, _why_ do we want to enable it? If you haven't measured the
actual power savings, then it's obviously not a primary reason.

As for the v5 targets only, they start from SDM845. Have you tested it?
Does it bring any actual benefits?

-- 
With best wishes
Dmitry