On 04/06/18 09:42, Helmut Grohne wrote:
> Work around repeated:
>
> mmc0: error -84 whilst initialising SD card
> ---
> drivers/mmc/host/sdhci.c | 1 +
> 1 file changed, 1 insertion(+)
>
> I'm seeing the above error -84 with a series of Kingston cards of 4GB capacity
> when used with an arasan host controller. Using the cards with other hosts or
> using other cards with the host is not problematic. The host controller has the
> following device tree:
>
> ps7-sdio@e0100000 {
> compatible = "arasan,sdhci-8.9a";
> reg = <0xe0100000 0x1000>;
> clock-names = "clk_xin", "clk_ahb";
> clock-frequency = <50000000>;
> clocks = <&clkc 21>, <&clkc 32>;
> interrupt-parent = <&ps7_scugic_0>;
> interrupts = <0 24 4>;
> };
>
> When enabling sufficient debugging (and thus slowing the kernel down), the
> problem goes away. Without debug features, the insertion of this delay suffices
> for my particular instance. Inserting the same delay before the
> SDHCI_CLOCK_CARD_EN write also makes the error go away.
>
> While instrumenting the code I found that the loop waiting for the
> SDHCI_CLOCK_INT_STABLE would always terminate immediately (regardless of the
> card being used). Only when the card is removed, the loop would spin once. This
> hints that potentially the stable checking is broken for this host controller.
>
> During my testing I checked 7 Kingston cards, 2 Transcend Cards, 1 Apacer card,
> 3 arasn hosts, 3 non-arasan hosts and had consistent reports for a similar
> number of devices from others.
>
> If my hypothesis is reasonable, I can turn this patch into a new quirk that
> replaces the stable polling with msleep(20), which is the poll timeout. Is
> there anything else I should investigate before doing so?
Please avoid quirks. Perhaps use the ->set_clock() callback.
>
> Helmut
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 90cc1977b792..5d2809aeb4eb 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -1430,6 +1430,7 @@ void sdhci_enable_clk(struct sdhci_host *host, u16 clk)
>
> clk |= SDHCI_CLOCK_CARD_EN;
> sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
> + udelay(80);
> }
> EXPORT_SYMBOL_GPL(sdhci_enable_clk);
>
>
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