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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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