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

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

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On Fri, 7 Apr 2023, Xu Yilun wrote:

> 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@intel.com>
> > Signed-off-by: Russ Weight <russell.h.weight@intel.com>
> > Co-developed-by: Xu Yilun <yilun.xu@intel.com>
> > Signed-off-by: Xu Yilun <yilun.xu@intel.com>
> > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> > ---
> >  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?

It seems to be safe to remove them so I dropped it.

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