Re: [PATCH 4/4] mfd: intel-m10-bmc: Manage access to MAX 10 fw handshake registers

[Xu Yilun]

On 2023-04-05 at 11:01:52 +0300, Ilpo Järvinen wrote:
> On some MAX 10 cards, the BMC firmware is not available to service
> handshake registers during secure update erase and write phases at
> normal speeds. This problem affects at least hwmon driver. When the MAX
> 10 hwmon driver tries to read the sensor values during a secure update,
> the reads are slowed down (e.g., reading all D5005 sensors takes ~24s
> which is magnitudes worse than the normal <0.02s).
> 
> Manage access to the handshake registers using a rw semaphore and a FW
> state variable to prevent accesses during those secure update phases
> and return -EBUSY instead.
> 
> Co-developed-by: Russ Weight <russell.h.weight@xxxxxxxxx>
> Signed-off-by: Russ Weight <russell.h.weight@xxxxxxxxx>
> Co-developed-by: Xu Yilun <yilun.xu@xxxxxxxxx>
> Signed-off-by: Xu Yilun <yilun.xu@xxxxxxxxx>
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
> ---
>  drivers/fpga/intel-m10-bmc-sec-update.c | 17 +++++--
>  drivers/mfd/intel-m10-bmc-core.c        | 63 ++++++++++++++++++++++++-
>  drivers/mfd/intel-m10-bmc-pmci.c        |  4 ++
>  drivers/mfd/intel-m10-bmc-spi.c         | 14 ++++++
>  include/linux/mfd/intel-m10-bmc.h       | 27 +++++++++++
>  5 files changed, 120 insertions(+), 5 deletions(-)
>

[...]
 
>  
> +static const struct regmap_range null_fw_handshake_regs[0];
> +
>  static const struct m10bmc_csr_map m10bmc_n6000_csr_map = {
>  	.base = M10BMC_N6000_SYS_BASE,
>  	.build_version = M10BMC_N6000_BUILD_VER,
> @@ -375,6 +377,8 @@ static const struct m10bmc_csr_map m10bmc_n6000_csr_map = {
>  static const struct intel_m10bmc_platform_info m10bmc_pmci_n6000 = {
>  	.cells = m10bmc_pmci_n6000_bmc_subdevs,
>  	.n_cells = ARRAY_SIZE(m10bmc_pmci_n6000_bmc_subdevs),
> +	.handshake_sys_reg_ranges = null_fw_handshake_regs,
> +	.handshake_sys_reg_nranges = 0,

Not sure why a zero length array is needed? Could we just remove
these 2 lines?

Thanks,
Yilun