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    SubjectRe: [PATCH v2 4/5] mmc: dw_mmc: Fix the DTO timeout calculation
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    On 2017/10/13 4:11, Douglas Anderson wrote:
    > Just like the CTO timeout calculation introduced recently, the DTO
    > timeout calculation was incorrect. It used "bus_hz" but, as far as I
    > can tell, it's supposed to use the card clock. Let's account for the
    > div value, which is documented as 2x the value stored in the register,
    > or 1 if the register is 0.
    >
    > NOTE: This was likely not terribly important until commit 16a34574c6ca
    > ("mmc: dw_mmc: remove the quirks flags") landed because "DIV" is
    > documented on Rockchip SoCs (the ones that used to define the quirk)
    > to always be 0 or 1. ...and, in fact, it's documented to only be 1
    > with EMMC in 8-bit DDR52 mode. Thus before the quirk was applied to
    > everyone it was mostly OK to ignore the DIV value.
    >
    > I haven't personally observed any problems that are fixed by this
    > patch but I also haven't tested this anywhere with a DIV other an 0.
    > AKA: this problem was found simply by code inspection and I have no
    > failing test cases that are fixed by it. Presumably this could fix
    > real bugs for someone out there, though.
    >
    > Fixes: 16a34574c6ca ("mmc: dw_mmc: remove the quirks flags")
    > Signed-off-by: Douglas Anderson <dianders@chromium.org>

    Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com>

    > ---
    >
    > Changes in v2:
    > - Fix the DTO timeout calculation new for v2
    >
    > drivers/mmc/host/dw_mmc.c | 8 +++++++-
    > 1 file changed, 7 insertions(+), 1 deletion(-)
    >
    > diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
    > index 50148991f30e..6bc87b1385a9 100644
    > --- a/drivers/mmc/host/dw_mmc.c
    > +++ b/drivers/mmc/host/dw_mmc.c
    > @@ -1936,10 +1936,16 @@ static int dw_mci_data_complete(struct dw_mci *host, struct mmc_data *data)
    > static void dw_mci_set_drto(struct dw_mci *host)
    > {
    > unsigned int drto_clks;
    > + unsigned int drto_div;
    > unsigned int drto_ms;
    > + unsigned long irqflags;
    >
    > drto_clks = mci_readl(host, TMOUT) >> 8;
    > - drto_ms = DIV_ROUND_UP(drto_clks, host->bus_hz / 1000);
    > + drto_div = (mci_readl(host, CLKDIV) & 0xff) * 2;
    > + if (drto_div == 0)
    > + drto_div = 1;
    > + drto_ms = DIV_ROUND_UP(MSEC_PER_SEC * drto_clks * drto_div,
    > + host->bus_hz);
    >
    > /* add a bit spare time */
    > drto_ms += 10;
    >

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