linux-kernel - Re: [PATCH v4 0/2] Fix LPSS clock divider for XPS 9530

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Date: Thu, 21 Dec 2023 22:12:59 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Aleksandrs Vinarskis <alex.vinarskis@...il.com>
Cc: Lee Jones <lee@...nel.org>, linux-kernel@...r.kernel.org,
	Hans de Goede <hdegoede@...hat.com>
Subject: Re: [PATCH v4 0/2] Fix LPSS clock divider for XPS 9530

On Thu, Dec 21, 2023 at 07:51:40PM +0100, Aleksandrs Vinarskis wrote:
> Dell XPS 9530 (2023) uses spi-pxa2xx with clock-divider enabled from
> intel-lpss with the ratio of 1:32767 (Dell's firmware bug). This caps SPI
> controller's speed at very low value of 3051Hz, which makes the interface
> practically unusable. Since either spi-pxa2xx or intel-lpss should have
> clock divider enabled, not both, and SPI controller can have higher speed
> than requested by the device, it is preffered to disable intel-lpss
> clock-divider, and let SPI controller handle it.
> 
> Fixing this issue directly in Dell firmware by setting lpss divider to 1:1
> would've been the ideal solution, but is unlikely to ever happen.
> 
> Particular driver already implements customized solution for handling buggy
> ACPI tables for select Microsoft devices. This patch series converts it to
> a more generic quirk table, and adds a new quirk QUIRK_CLOCK_DIVIDER_UNITY
> which forces clock divider to be set to 1:1. In the future, devices with
> similar bug (if any) can be easily added to the same pci id lookup table.

LGTM now,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

-- 
With Best Regards,
Andy Shevchenko