On Tue, Feb 22, 2022 at 11:28:18AM +0800, haibo.c...@nxp.com wrote:
> From: Haibo Chen <haibo.c...@nxp.com>
>
> After commit f132aab40327 ("Revert "mmc: fsl_esdhc_imx: use
> VENDORSPEC_FRC_SDCLK_ON to control card clock output""), it
> involve issue in mmc_switch_voltage(), because of the special
> design of usdhc.
>
> For FSL_USDHC, it do not implement VENDORSPEC_CKEN/PEREN/HCKEN/IPGEN,
> these are reserved bits(Though RM contain the definition of these bits,
> but actually internal IC logic do not implement, already confirm with
> IC team). Instead, use VENDORSPEC_FRC_SDCLK_ON to gate on/off the card
> clock output. Here is the definition of this bit in RM:
>
> [8] FRC_SDCLK_ON
> Force CLK output active
> Do not set this bit to 1 unless it is necessary. Also, make sure that
> this bit is cleared when uSDHC’s clock is about to be changed (frequency
> change, clock source change, or delay chain tuning).
> 0b - CLK active or inactive is fully controlled by the hardware.
> 1b - Force CLK active
>
> In default, the FRC_SDCLK_ON is 0. This means, when there is no command
> or data transfer on bus, hardware will gate off the card clock. But in
> some case, we need the card clock keep on. Take IO voltage 1.8v switch
> as example, after IO voltage change to 1.8v, spec require gate off the
> card clock for 5ms, and gate on the clock back, once detect the card
> clock on, then the card will draw the dat0 to high immediately. If there
> is not clock gate off/on behavior, some card will keep the dat0 to low
> level. This is the reason we fail in mmc_switch_voltage().
>
> To fix this issue, and concern that this is only the fsl usdhc hardware
> design limitation, set the bit FRC_SDCLK_ON in the beginning of the
> wait_dat0() and clear it in the end. To make sure the 1.8v IO voltage
> switch process align with SD specification.
>
> For standard tuning process, usdhc specification also require the card
> clock keep on, so also add these behavior in fsl_esdhc_execute_tuning().
>
> Reviewed-by: Marek Vasut <ma...@denx.de>
> Tested-by: Fabio Estevam <feste...@gmail.com>
> Signed-off-by: Haibo Chen <haibo.c...@nxp.com>
> Reviewed-by: Peng Fan <peng....@nxp.com>
> Reviewed-by: Jaehoon Chung <jh80.ch...@samsung.com>
> ---
> drivers/mmc/fsl_esdhc_imx.c | 25 ++++++++++++++++++++++---
> include/fsl_esdhc_imx.h | 2 ++
> 2 files changed, 24 insertions(+), 3 deletions(-)Is this going to get picked up in the imx or mmc trees soon, or should I take this directly? Thanks! -- Tom
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