linux-kernel - Re: [PATCH v3 1/5] misc: eeprom: eeprom_93cx6: Add quirk for extra read clock cycle

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Message-ID: <Zv1YUyzL41GTqsOA@smile.fi.intel.com>
Date: Wed, 2 Oct 2024 17:27:31 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Parker Newman <parker@...est.io>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>, Arnd Bergmann <arnd@...db.de>,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
	Parker Newman <pnewman@...necttech.com>
Subject: Re: [PATCH v3 1/5] misc: eeprom: eeprom_93cx6: Add quirk for extra
 read clock cycle

On Wed, Oct 02, 2024 at 10:14:07AM -0400, Parker Newman wrote:
> From: Parker Newman <pnewman@...necttech.com>
> 
> Add a quirk similar to eeprom_93xx46 to add an extra clock cycle before
> reading data from the EEPROM.
> 
> The 93Cx6 family of EEPROMs output a "dummy 0 bit" between the writing
> of the op-code/address from the host to the EEPROM and the reading of
> the actual data from the EEPROM.
> 
> More info can be found on page 6 of the AT93C46 datasheet (linked below).
> Similar notes are found in other 93xx6 datasheets.
> 
> In summary the read operation for a 93Cx6 EEPROM is:
> Write to EEPROM:	110[A5-A0]	(9 bits)
> Read from EEPROM:	0[D15-D0]	(17 bits)
> 
> Where:
> 	110 is the start bit and READ OpCode
> 	[A5-A0] is the address to read from
> 	0 is a "dummy bit" preceding the actual data
> 	[D15-D0] is the actual data.
> 
> Looking at the READ timing diagrams in the 93Cx6 datasheets the dummy
> bit should be clocked out on the last address bit clock cycle meaning it
> should be discarded naturally.
> 
> However, depending on the hardware configuration sometimes this dummy
> bit is not discarded. This is the case with Exar PCI UARTs which require
> an extra clock cycle between sending the address and reading the data.

...

> +static inline bool has_quirk_extra_read_cycle(struct eeprom_93cx6 *eeprom)
> +{
> +	return eeprom->quirks & PCI_EEPROM_QUIRK_EXTRA_READ_CYCLE;
> +}

> +

Seems to me the redundant new line at the end of file.


-- 
With Best Regards,
Andy Shevchenko