mmc: host: meson-mx-sdhc: new driver for the Amlogic Meson SDHC host
The SDHC MMC host controller on Amlogic SoCs provides an eMMC and MMC card interface with 1/4/8-bit bus width. It supports eMMC spec 4.4x/4.5x including HS200 (up to 100MHz clock). The public S805 datasheet [0] contains a short documentation about the registers. Unfortunately it does not describe how to use the registers to make the hardware work. Thus this driver is based on reading (and understanding) the Amlogic 3.10 GPL kernel code. Some hardware details are not easy to see. Jianxin Pan was kind enough to answer my questions: The hardware has built-in busy timeout support. The maximum timeout is 30 seconds. This is only documented in Amlogic's internal documentation. The controller only works with very specific clock configurations. The details are not part of the public datasheet. In my own words the supported configurations are: - 399.812kHz: clkin = 850MHz div = 2126 sd_rx_phase = 63 - 1MHz: clkin = 850MHz div = 850 sd_rx_phase = 55 - 5.986MHz: clkin = 850MHz div = 142 sd_rx_phase = 24 - 25MHz: clkin = 850MHz div = 34 sd_rx_phase = 15 - 47.222MHz: clkin = 850MHz div = 18 sd_rx_phase = 11/15 (SDR50/HS) - 53.125MHz: clkin = 850MHz div = 16 sd_rx_phase = (tuning) - 70.833MHz: clkin = 850MHz div = 12 sd_rx_phase = (tuning) - 85MHz: clkin = 850MHz div = 10 sd_rx_phase = (tuning) - 94.44MHz: clkin = 850MHz div = 9 sd_rx_phase = (tuning) - 106.25MHz: clkin = 850MHz div = 8 sd_rx_phase = (tuning) - 127.5MHz: clkin = 1275MHz div = 10 sd_rx_phase = (tuning) - 141.667MHz: clkin = 850MHz div = 6 sd_rx_phase = (tuning) - 159.375MHz: clkin = 1275MHz div = 8 sd_rx_phase = (tuning) - 212.5MHz: clkin = 1275MHz div = 6 sd_rx_phase = (tuning) - (sd_tx_phase is always 1, 94.44MHz is not listed in the datasheet but this is what the 3.10 BSP kernel on Odroid-C1 actually uses) NOTE: CMD23 support is disabled for now because it results in command timeouts and thus decreases read performance. Tested-by:Wei Wang <lnykww@gmail.com> Tested-by:
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