On Tue, Feb 22, 2022 at 11:28:18AM +0800, haibo.chen@nxp.com wrote:
From: Haibo Chen haibo.chen@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 marex@denx.de Tested-by: Fabio Estevam festevam@gmail.com Signed-off-by: Haibo Chen haibo.chen@nxp.com Reviewed-by: Peng Fan peng.fan@nxp.com Reviewed-by: Jaehoon Chung jh80.chung@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!