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

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Date:   Tue, 11 Apr 2023 14:54:58 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Xu Yilun <yilun.xu@...el.com>
cc:     Wu Hao <hao.wu@...el.com>, Tom Rix <trix@...hat.com>,
        Moritz Fischer <mdf@...nel.org>, linux-fpga@...r.kernel.org,
        Lee Jones <lee@...nel.org>, Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        linux-hwmon@...r.kernel.org,
        Russ Weight <russell.h.weight@...el.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] mfd: intel-m10-bmc: Manage access to MAX 10 fw
 handshake registers

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@...el.com>
> > Signed-off-by: Russ Weight <russell.h.weight@...el.com>
> > Co-developed-by: Xu Yilun <yilun.xu@...el.com>
> > Signed-off-by: Xu Yilun <yilun.xu@...el.com>
> > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.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(-)
> >
> 
> [...]
>  
> >  
> > +void m10bmc_fw_state_set(struct intel_m10bmc *m10bmc, enum m10bmc_fw_state new_state)
> > +{
> > +	down_write(&m10bmc->bmcfw_lock);
> > +	m10bmc->bmcfw_state = new_state;
> > +	up_write(&m10bmc->bmcfw_lock);
> 
> Could we also skip this if no handshake is possible like for PMCI?

Did you mean guarding it with !m10bmc->info->handshake_sys_reg_nranges ?
If yes, it's doable (+ I'd add comment mentioning it since it's slightly 
trappy to not always have that state updated).


-- 
 i.