On Fri, 2021-09-24 at 16:26 +0300, Adrian Hunter wrote:

On 24/09/21 4:08 pm, Bean Huo wrote:

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On Fri, 2021-09-24 at 15:17 +0300, Adrian Hunter wrote:

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         sdhci_writeb(host, count, SDHCI_TIMEOUT_CONTROL);
}
The driver has detected that the hardware timer cannot meet
the
timeout
requirements of the device, but we still use the hardware
timer,
which will
allow potential timeout issuea . Rather than allowing a
potential
problem to exist, why can’t software timing be used to
avoid
this
problem?

Timeouts aren't that accurate.  The maximum is assumed still
to
work.
mmc->max_busy_timeout is used to tell the core what the
maximum
is.

mmc->max_busy_timeout is still a representation of Host HW
timer
maximum timeout count, isn't it? 

Not necessarily.  For SDHCI_QUIRK2_DISABLE_HW_TIMEOUT it would be

set to zero to indicate no maximum.

yes, this is the purpose of the patch, for the host controller
without
quirk SDHCI_QUIRK2_DISABLE_HW_TIMEOUT, if the timeout count
required by
device is beyond the HW timer max count, we choose SW timer to
avoid the HW timer timeout IRQ.

I don't know if I get it correctly.

Why can't drivers that want the behaviour just set the quirk?

Drivers that do not work with the quirk, do not have to set it.

Adrian,

We cannot add this quirk to every host driver. This is the difference
on the device side. In addition, I don't know what the maximum hardware
timer budget for each host is. Even if you use the same SOC, the
maximum time budget on different platforms may be different.

Assume that the maximum timeout time supported by the hardware timer is
100 milliseconds, but the maximum data transmission time required by
the device is 150 milliseconds. In most cases, data transfer will not
take so long. 150 is the maximum time under extreme conditions. This
means that the device just needs to complete a data transfer within

100ms and keep the data line busy. If we still use the HW timer, it

will trigger a DATA LINE timeout interrupt.

This patch does not affect scenarios where the hardware timer meets the
max data transmission time requirements of the device. It will still
use the hardware timer. Only when the device changes, will it switch to
using the SW timer.

Bean