• Viken Dadhaniya's avatar
    i2c: qcom-geni: Correct I2C TRE sequence · 83ef106f
    Viken Dadhaniya authored
    For i2c read operation in GSI mode, we are getting timeout
    due to malformed TRE basically incorrect TRE sequence
    in gpi(drivers/dma/qcom/gpi.c) driver.
    
    I2C driver has geni_i2c_gpi(I2C_WRITE) function which generates GO TRE and
    geni_i2c_gpi(I2C_READ)generates DMA TRE. Hence to generate GO TRE before
    DMA TRE, we should move geni_i2c_gpi(I2C_WRITE) before
    geni_i2c_gpi(I2C_READ) inside the I2C GSI mode transfer function
    i.e. geni_i2c_gpi_xfer().
    
    TRE stands for Transfer Ring Element - which is basically an element with
    size of 4 words. It contains all information like slave address,
    clk divider, dma address value data size etc).
    
    Mainly we have 3 TREs(Config, GO and DMA tre).
    - CONFIG TRE : consists of internal register configuration which is
                   required before start of the transfer.
    - DMA TRE :    contains DDR/Memory address, called as DMA descriptor.
    - GO TRE :     contains Transfer directions, slave ID, Delay flags, Length
                   of the transfer.
    
    I2c driver calls GPI driver API to config each TRE depending on the
    protocol.
    
    For read operation tre sequence will be as below which is not aligned
    to hardware programming guide.
    
    - CONFIG tre
    - DMA tre
    - GO tre
    
    As per Qualcomm's internal Hardware Programming Guide, we should configure
    TREs in below sequence for any RX only transfer.
    
    - CONFIG tre
    - GO tre
    - DMA tre
    
    Fixes: d8703554 ("i2c: qcom-geni: Add support for GPI DMA")
    Reviewed-by: default avatarAndi Shyti <andi.shyti@kernel.org>
    Reviewed-by: default avatarBryan O'Donoghue <bryan.odonoghue@linaro.org>
    Tested-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org> # qrb5165-rb5
    Co-developed-by: default avatarMukesh Kumar Savaliya <quic_msavaliy@quicinc.com>
    Signed-off-by: default avatarMukesh Kumar Savaliya <quic_msavaliy@quicinc.com>
    Signed-off-by: default avatarViken Dadhaniya <quic_vdadhani@quicinc.com>
    Reviewed-by: default avatarDmitry Baryshkov <dmitry.baryshkov@linaro.org>
    Signed-off-by: default avatarAndi Shyti <andi.shyti@kernel.org>
    83ef106f
i2c-qcom-geni.c 26.8 KB