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Subject: Re: [baylibre-upstreaming] [PATCH 0/3] mmc: meson-gx: add
 ddr-access-quirk support
To:     baylibre-upstreaming@groups.io, narmstrong@baylibre.com,
        ulf.hansson@linaro.org, khilman@baylibre.com
Cc:     linux-mmc@vger.kernel.org, linux-amlogic@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
References: <20190513091548.16674-1-narmstrong@baylibre.com>
From:   guillaume La Roque <glaroque@baylibre.com>
Message-ID: <65423579-52c0-40ca-143a-6bc6ed33c90e@baylibre.com>
Date:   Tue, 14 May 2019 11:14:53 +0200
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On 5/13/19 11:15 AM, Neil Armstrong wrote:
> On the Amlogic G12A SoC family, (only) the SDIO controller fails to access
> the data from DDR, leading to a broken controller.
>
> Add the amlogic,ddr-access-quirk property so signal this particular
> controller has this bug and needs a quirk to work properly.
>
> But each MMC controller has 1,5KiB of SRAM after the registers, that can
> be used as bounce buffer to avoid direct DDR access from the integrated
> DMAs (this SRAM may be used by the boot ROM when DDR is not yet initialized).
>
> The quirk is to disable the chained descriptor for this controller, and
> use this SRAM memory zone as buffer for the bounce buffer fallback mode.
>
> The performance hit hasn't been evaluated, but the fix has been tested
> using a WiFi AP6398S SDIO module, and the iperf3 Bandwidth measurement gave
> 55.2 Mbits/sec over a 63 Hours long test, with the SDIO ios set as High-Speed
> at 50MHz clock. It gave around 170 Mbits/sec as SDR104 and 200MHz clock.
>
> Neil Armstrong (3):
>   dt-bindings: mmc: meson-gx: add ddr-access-quirk property
>   mmc: meson-gx: add ddr-access-quirk
>   arm64: dts: meson-g12a: add ddr-access-quirk property to SDIO
>     controller
>
>  .../bindings/mmc/amlogic,meson-gx.txt         |  4 ++
>  arch/arm64/boot/dts/amlogic/meson-g12a.dtsi   |  1 +
>  drivers/mmc/host/meson-gx-mmc.c               | 65 +++++++++++++++----
>  3 files changed, 57 insertions(+), 13 deletions(-)
>
Test with SEI510 board no problem or regression seen

Tested-by: Guillaume La Roque <glaroque@baylibre.com>