Re: [PATCH V1] mmc: sdhci: Update the software timeout value for sdhc

[Doug Anderson <dianders@chromium.org>]

Hi,

On Fri, Jun 18, 2021 at 8:31 AM Veerabhadrarao Badiganti
<vbadigan@codeaurora.org> wrote:
>
>
> On 6/16/2021 2:55 PM, Shaik Sajida Bhanu wrote:
> > Whenever SDHC run at clock rate 50MHZ or below, the hardware data
> > timeout value will be 21.47secs, which is approx. 22secs and we have
> > a current software timeout value as 10secs. We have to set software
> > timeout value more than the hardware data timeout value to avioid seeing
> > the below register dumps.
> >
> > [  332.953670] mmc2: Timeout waiting for hardware interrupt.
> > [  332.959608] mmc2: sdhci: ============ SDHCI REGISTER DUMP ===========
> > [  332.966450] mmc2: sdhci: Sys addr:  0x00000000 | Version:  0x00007202
> > [  332.973256] mmc2: sdhci: Blk size:  0x00000200 | Blk cnt:  0x00000001
> > [  332.980054] mmc2: sdhci: Argument:  0x00000000 | Trn mode: 0x00000027
> > [  332.986864] mmc2: sdhci: Present:   0x01f801f6 | Host ctl: 0x0000001f
> > [  332.993671] mmc2: sdhci: Power:     0x00000001 | Blk gap:  0x00000000
> > [  333.000583] mmc2: sdhci: Wake-up:   0x00000000 | Clock:    0x00000007
> > [  333.007386] mmc2: sdhci: Timeout:   0x0000000e | Int stat: 0x00000000
> > [  333.014182] mmc2: sdhci: Int enab:  0x03ff100b | Sig enab: 0x03ff100b
> > [  333.020976] mmc2: sdhci: ACmd stat: 0x00000000 | Slot int: 0x00000000
> > [  333.027771] mmc2: sdhci: Caps:      0x322dc8b2 | Caps_1:   0x0000808f
> > [  333.034561] mmc2: sdhci: Cmd:       0x0000183a | Max curr: 0x00000000
> > [  333.041359] mmc2: sdhci: Resp[0]:   0x00000900 | Resp[1]:  0x00000000
> > [  333.048157] mmc2: sdhci: Resp[2]:   0x00000000 | Resp[3]:  0x00000000
> > [  333.054945] mmc2: sdhci: Host ctl2: 0x00000000
> > [  333.059657] mmc2: sdhci: ADMA Err:  0x00000000 | ADMA Ptr:
> > 0x0000000ffffff218
> > [  333.067178] mmc2: sdhci_msm: ----------- VENDOR REGISTER DUMP
> > -----------
> > [  333.074343] mmc2: sdhci_msm: DLL sts: 0x00000000 | DLL cfg:
> > 0x6000642c | DLL cfg2: 0x0020a000
> > [  333.083417] mmc2: sdhci_msm: DLL cfg3: 0x00000000 | DLL usr ctl:
> > 0x00000000 | DDR cfg: 0x80040873
> > [  333.092850] mmc2: sdhci_msm: Vndr func: 0x00008a9c | Vndr func2 :
> > 0xf88218a8 Vndr func3: 0x02626040
> > [  333.102371] mmc2: sdhci: ============================================
> >
> > So, set software timeout value more than hardware timeout value.
> >
> > Signed-off-by: Shaik Sajida Bhanu <sbhanu@codeaurora.org>
> > ---
> >   drivers/mmc/host/sdhci.c | 9 ++++++++-
> >   1 file changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> > index bf238ad..1386f7d 100644
> > --- a/drivers/mmc/host/sdhci.c
> > +++ b/drivers/mmc/host/sdhci.c
> > @@ -1670,7 +1670,14 @@ static bool sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
> >       else if (!cmd->data && cmd->busy_timeout > 9000)
> >               timeout += DIV_ROUND_UP(cmd->busy_timeout, 1000) * HZ + HZ;
> >       else
> > -             timeout += 10 * HZ;
> > +            /*
> > +             * In some of the conditions hardware data timeout value could be
> > +             * approx 21.5 seconds and driver is setting software data timeout
> > +             * value less than the hardware data timeout value and software data
> > +             * timeout value should be more than the hardware data timeout value.
> > +             * So, set software data timeout value more than 21.5 sec i.e. 22sec.
> > +             */
> > +             timeout += 22 * HZ;
>
> This timeout is qcom SDHC specific.
> I think right way is to, define your own set_timeout op and update
> host->data_timeout
> in that as per qcom SDHC requirements.

It is? Off-thread Shaik was indicating that the problem had to do with
the inaccuracy of the "SDHCI_TIMEOUT_CONTROL" register. That seems to
be in the common SDHCI code. Specifically looking at
sdhci_calc_timeout() it can be seen that the possible hardware values
for the timeout double each time, so if you need a hardware timeout
that's slightly higher than one of the possible values you might end
up with a hardware timeout that's almost double what you want.

Assuming that the problem actually is with the inaccuracy of
SDHCI_TIMEOUT_CONTROL (I didn't walk through and validate), it
actually seems like we should generally be doubling the value we were
programming for the software timeout (in other words, not just ones
that are <= 9 seconds). I haven't done all the math, but I presume the
reason that we need 22 instead of 20 is some type of extra fudge
factor somewhere?

Maybe the only reason that Qualcomm hits this is due to the PLL that's
sourcing the SDHCI controller at a non-standard rate?

I suppose another reason maybe why people aren't hitting it is just
the random chance of what rate the integer overflow in
mmc_set_data_timeout() leaves you at? I pointed this out to Shiak and
was hoping a patch would be included for that, but I can always try to
write one later if not. To be concrete, I have
card->csd.taac_ns=5000000 and card->csd.r2w_factor=5. Multiplying
things out (and accounting for mult=100 for SD cards), I end up with a
timeout_ns of 0x3b9aca000 (16 seconds) which doesn't fit in the 32-bit
data->timeout_ns earlier. The truncation was making it look like the
card requested a max timeout of 3,115,098,112 ns = ~3.1 seconds.

-Doug